KICP in the News, 2011

Giant telescope could solve deep mysteries
The University of Chicago News Office, January 18, 2011
The Giant Magellan Telescope will combine seven 8.4-meter primary mirror segments into the equivalent of a 24.5-meter telescope.   <i>Photo courtesy of Giant Magellan Telescope - GMTO Corp.</i>
The Giant Magellan Telescope will combine seven 8.4-meter primary mirror segments into the equivalent of a 24.5-meter telescope.

Photo courtesy of Giant Magellan Telescope - GMTO Corp.
by Steve Koppes, The University of Chicago News Office

"Larger telescopes allow us to look farther out in space and further back in time to probe the very earliest history of the universe."
- Edward "Rocky" Kolb,
Arthur Holly Compton Distinguished Service Professor

Most of the starlight that hits the Earth falls into the oceans, "but coded into that light is the entire history of the universe."

So said Patrick McCarthy, project director of the Giant Magellan Telescope, during a recent visit to campus. The telescope, which could open as early as 2019, will peer more deeply into the universe's hidden history than humans have ever attempted. Scientists say the instrument's combined mirrors will be sensitive enough to detect a candle on the moon, or to see the face on a dime 200 miles away.

The possibilities have energized researchers at the University of Chicago, which is a founding member of the GMT Organization. Construction of the telescope will begin at the Las Campanas Observatory in Chile in two years. Experts say the facility is part of a long-term ambition to understand the nature of dark matter and dark energy, and to glimpse the formation and evolution of extrasolar planets, stars, galaxies, and black holes.

"When we study the evolution of the universe we can use telescopes as time machines," says Edward "Rocky" Kolb, chairman of UChicago's Department of Astronomy & Astrophysics and the Arthur Holly Compton Distinguished Service Professor. "Larger telescopes allow us to look farther out in space and further back in time to probe the very earliest history of the universe."

In addition to joining the GMT Organization in July, UChicago also secured access for its astronomers to the existing twin Magellan Telescopes at Las Campanas, perched high in the Chilean Andes, starting next year.

"The Magellan Telescopes will be our tool in optical astronomy for the next 10 years. Beyond that is the Giant Magellan Telescope," says Kolb.

The GMT will combine seven 8.4-meter primary mirror segments operating together as if they were part of a single, 24.5-meter telescope. Its capabilities will exceed those of even the Hubble Space Telescope.

The Search for 'Missing Matter'
The first of the GMT's primary mirrors has already been cast and is undergoing polishing at the University of Arizona's Steward Observatory Mirror Lab. "There's only one place in the world that can make these mirrors, and that's the University of Arizona Mirror Lab," Kolb says.

The GMT will address some of the biggest questions in astronomy, including how dark matter affects the movements of galaxies and galaxy clusters, and the role that dark energy has played in the evolution of the universe.

"We know that the universe is made of 74 percent dark energy, 22 percent dark matter, and 4 percent ordinary matter," says Hsiao-Wen Chen, Assistant Professor in Astronomy & Astrophysics. Chen is especially interested in the search for "dark" ordinary matter. This is the stuff of stars, planets and people, yet two-thirds of this dark matter remains missing.

"The missing matter underscores a serious shortfall in our knowledge of the growth of the visible universe," says Chen, who has made many trips to Las Campanas to use the twin 6.5-meter Magellan Telescopes for her research.

Space: Not empty
Even though space appears to be empty, it's not. How much more unseen matter is out there? How fast are the stars forming in the 'dark' universe? Will these faint objects eventually be captured by other known luminous galaxies?" Chen asks. "More powerful telescopes will help us to answer many of these outstanding questions."

Michael Gladders, Assistant Professor in Astronomy & Astrophysics, is another frequent UChicago visitor to Las Campanas. He built two instruments for the Magellan Telescopes as a fellow at the Carnegie Institution for Science before coming to UChicago a few years ago. He and his UChicago colleagues are now discussing instrumentation possibilities for the GMT.

The GMT partners have half a dozen instrument concepts currently under study and will select up to four of them for further development in fall 2011. As a founding partner of the GMT, UChicago will have an opportunity to help select and develop the new instruments.

These instruments are specialized attachments designed to enhance the investigation of various phenomena - searching for Earthlike planets around other stars, for example. "The opportunity to build instruments for a world-leading facility like this basically opens up scientific pathways that you cannot otherwise open," Gladders says.


Related Links:
KICP Members: Hsiao-Wen Chen; Michael D. Gladders; Edward W. Kolb
Scientific projects: Giant Magellan Telescope (GMT)

First light: Joining on to build the next biggest and best telescope, Chicago secures its astrophysics footing
University of Chicago Magazine, January 25, 2011
The twin Magellan telescopes at Chiles Las Campanas Observatory.
The twin Magellan telescopes at Chile's Las Campanas Observatory.
by Benjamin Recchie, University of Chicago Magazine

Over the next decade, an international team of scientists and engineers will construct a scientific behemoth high in the Andes Mountains. The Giant Magellan Telescope will be more than 200 feet high and weigh hundreds of tons. It will see the first stars that ever shone and Earth-like planets around distant suns. It will be more than four times larger than any optical telescope in existence today, and the University of Chicago will help to build it.


Related Links:
KICP Members: Hsiao-Wen Chen; Michael D. Gladders; Edward W. Kolb; Richard G. Kron
Scientific projects: Giant Magellan Telescope (GMT)

Richard Kron to chair Science Advisory Committee of Giant Magellan Telescope
The University of Chicago News Office, February 10, 2011
Richard Kron, KICP associate.
Richard Kron, KICP associate.
by Steve Koppes, The University of Chicago News Office

The Giant Magellan Telescope board of directors has appointed Richard Kron, Professor in Astronomy & Astrophysics, as chair of the GMT Science Advisory Committee, effective immediately.

"Richard has great experience in providing scientific advice and oversight to large projects," including the Columbus Project (now called the Large Binocular Telescope), the Sloan Digital Sky Survey and the Dark Energy Survey, said Patrick McCarthy, director of the GMT Organization.

Hsiao-Wen Chen will continue to serve as UChicago's SAC member. Last summer UChicago became a founding partner of the GMT - the effort to build the world's largest telescope in Chile.

In the next year, SAC will begin the process of selecting the GMT's first-generation suite of instruments. The committee also will review and update the facility's science case, update and finalize the top-level scientific and technical requirements, and update the operations procedures and formulate a science support and data plan.


Related Links:
KICP Members: Hsiao-Wen Chen; Richard G. Kron
Scientific projects: Giant Magellan Telescope (GMT)

Rogue Planets Could Harbor Life
Wired Science, February 11, 2011
Eric Switzer, KICP fellow, at the Atacama Cosmology Telescope, 17,000 ft.
Eric Switzer, KICP fellow, at the Atacama Cosmology Telescope, 17,000 ft.
by Lisa Grossman, Wired Science

If a planet is ripped from the warm cradle of its solar system and plunged into the frigid depths of space, it could still hold on to a liquid ocean - and maybe life - beneath an icy crust.

Planet formation models suggest that small planets are regularly flung from their solar systems by close encounters with neighboring gas giants. The giants' gravitational fields create an interplanetary slingshot effect, sending smaller planets on unstable orbits that quickly leave their star behind.

Prior to ejection, some of those planets could conceivably be like Earth, with continents, oceans and biospheres. A new model suggests that submarine aliens on such a planet could have a chance at survival.

"We originally started with the question, 'What if you turned off the sun?'" said University of Chicago geophysicist Dorian Abbot, co-author of a paper submitted to Astrophysical Journal Letters and prepublished Feb. 5 on

Along with fellow University of Chicago astrophysicist Eric Switzer, Abbot ran the numbers to see if an ocean could stay liquid without heat from a star. They called their rogue world a Steppenwolf planet, "since any life in this strange habitat would exist like a lone wolf wandering the galactic steppe."

The pair assumed the planet was between 0.1 and 10 times Earth's mass, with a similar amount of water and rock. Once the planet was flung its warm, nurturing star, the ocean would start to freeze. But leftover heat from the planet's formation and decaying radioactive elements in the rock could keep the ocean warm beneath a shell of ice. As long as the planet could keep the ice from freezing all the way to the core, the ocean should be safe.

Abbot and Switzer calculated that a planet 3.5 times the mass of Earth would be warm enough at the core to maintain a liquid ocean beneath an ice crust a few kilometers thick. The ocean could last for about 5 billion years.

"That's a non-ridiculously short timescale," said astrobiologist Cynthia Phillips of the SETI Institute, who was not involved in the new work. "It seems like this thick ocean could actually persist for longer than you might assume, without going through the numbers."

Phillips studies the possibility of life beneath the icy crust of Jupiter's moon Europa, a world superficially similar to the hypothetical Steppenwolf planet. But unlike the rogue world, most of Europa's heat comes from tides raised by Jupiter.

In a slightly more bizarre twist, Switzer and Abbot imagined the Steppenwolf planet with volcanoes spewing carbon dioxide into the atmosphere. The gas would freeze and fall as snow almost immediately, covering the world with an insulating blanket of dry ice. In that case, planets as small as 0.3 times the mass of Earth could keep a liquid ocean.

"That, I'm a bit more dubious about," Phillips said. With only decaying radioactive elements providing heat, "it seems unlikely that you'd have serious volcanic activity going on, without any other energy present."

Life on the planet could consist not only of organisms that survived the interstellar turmoil and adapted, but those that evolved later, around hydrothermal vents at ocean floors.

Abbot and Switzer declined to speculate what such life would look like, but they and Phillips agreed that it would almost certainly be microscopic.

"I would be very, very surprised if a planet like this could sustain big macroscopic life forms, just because the energy is so limited," Phillips said.

If these inhabited, free-floating planets exist, they could have been a vehicle for bringing the seeds of life to Earth. If the planet came within about 0.01 light-years of Earth, it could even be observed from the ground, Abbot and Switzer suggested.

But the odds of that happening about one in a billion at best, Switzer said. The researchers mostly meant to muse on the extreme possibilities for habitable worlds.

"If you can imagine life on such an object," Abbot said, "potentially there could be life in many sorts of weird situations that we haven't thought of before."


Related Links:
KICP Members: Eric Switzer

U. of C. gets serious about stargazing: University invests millions, gaining access to telescopes in Chile
Chicago Tribune, February 16, 2011
Edward Rocky Kolb, KICP senior member.   Image credit: Zbigniew Bzdak
Edward "Rocky" Kolb, KICP senior member.

Image credit: Zbigniew Bzdak
by Hailey Branson-Potts, Chicago Tribune

If astronomy were a religion, telescopes would be the cathedrals, says Matt Bayliss, an astronomy and astrophysics doctoral student at the University of Chicago.

"There's just something about working with telescopes," Bayliss said. "They are very romantic. You're working outside, and you're working with a very unique piece of equipment."

For U. of C. students like Bayliss, the opportunities to work with massive optical telescopes around the world are increasing. In the past year, the university has invested millions of dollars to gain exclusive access to two top-tier telescopes in Chile and has committed to help build the world's largest telescope - the Giant Magellan Telescope - within the next decade.

The new emphasis on and access to these tools will create one of the leading astronomy and astrophysics departments in the world, said the department's chair, Edward "Rocky" Kolb.


Related Links:
KICP Members: Hsiao-Wen Chen; Edward W. Kolb
KICP Students: Matthew B. Bayliss; Megan B. Gralla
Scientific projects: Giant Magellan Telescope (GMT)

Bruce Winstein
Cosmic Variance, Discover Magazine, February 28, 2011
by Sean Carroll, Cosmic Variance, Discover Magazine

Bruce Winstein, an experimental physicist at the University of Chicago, passed away this morning. He had been fighting cancer.

Bruce was a fantastic physicist and person. He became well-known as a particle experimentalist, forgoing giant collaborations to work in small groups where he could do something unique. He was the leader of the KTeV experiment at Fermilab, which measured the very subtle "direct" CP violation effect. He won the Panofsky Prize from the American Physical Society for this work.

In an especially impressive move, he then decided that he wanted to switch fields, into cosmology. He took a sabbatical year and went to Princeton, where he basically worked as a grad student in Suzanne Staggs' lab, learning the trade of cosmic microwave background observations from the ground up. Then he came back to Chicago, where he started and was the founding director of the Center for Cosmological Physics, later the Kavli Institute for Cosmological Physics. Once that was up and running, he moved back into research full-time, becoming a leader of the QUIET collaboration.

Bruce was a great friend, and a valued mentor while I was at Chicago. He was one of the few faculty members to reach out and invite me into his office when I arrived, and was always ready to talk about physics - or music. He was a true audiophile, and connoisseur of jazz in particular. It was Bruce who introduced me to the music of Von Freeman (who just won the prestigious Rosenberger Medal from the University of Chicago).

Bruce died far too young. We'll miss him greatly.


Related Links:
KICP Members: Bruce D. Winstein

Bruce Winstein, physicist, 1943-2011
The University of Chicago News Office, March 2, 2011
Bruce D. Winstein
Bruce D. Winstein
by Sarah Galer, The University of Chicago News Office

Bruce Winstein, an experimental physicist who studied the afterglow of the universe's birth, died Feb. 28 after a four-year battle with cancer. He was 67.

Winstein, the Samuel K. Allison Distinguished Service Professor in Physics, the Enrico Fermi Institute and the College, was known as a punctilious leader of experiments measuring the aftermath of the big bang in two fundamental fields of physics - particle physics and cosmology.

A strong advocate of "blinded" measurements, in which scientists intentionally conceal the final answer while analyzing data to prevent their preconceptions from influencing the result, he imported many practices of particle physics after his mid-career switch into cosmology, the study of the early universe,. "Psychologically, it's better," Winstein told an interviewer in 2000. "There's no concern about, 'Do we agree with our old experiment?'"

In 1999, after 25 years of increasingly precise measurements at the Fermi National Accelerator Laboratory, Winstein and colleagues produced the first definitive evidence of "direct" CP violation - proof that matter and anti-matter, once thought to be mirror opposites, are not perfect twins. The result showed that the direction time flows, from past to future, is part of the fundamental laws of the universe. The size of the finding produced an "audible gasp" from the Fermilab audience, reports said. In accordance with the "blinded" technique, Winstein had not known the results until the days before the announcement.

"Bruce had the skill and the passion to measure that quantity to whatever precision necessary," said James Cronin, the University Professor Emeritus in Physics, who won the Nobel Prize in 1980 for the discovery of CP violation. "The experiments took extraordinary sensitivity and attention to detail."

"Bruce was an extraordinary experimentalist who applied what he learned from particle physics directly to the field of cosmology," said Stephan Meyer, Associate Director of Astronomy & Astrophysics. "The result was a new experiment using a different approach and different instrumentation - a great thing for difficult and subtle measurements."

At a daylong "Brucefest" retirement party hosted by UChicago last month, former students recalled Winstein as an intense experimenter. "I remember, with surprising fondness, your regular 11 p.m. call asking what I'd learned since dinner," said Ritchie Patterson, the Department Chair of Physics at Cornell University and a doctoral student of Winstein's in the 1980s.

Outside the lab, Winstein was a mischievous presence. He arranged increasingly elaborate and red-herring-filled surprise birthday parties for his wife, Joan, through 32 years of marriage, and loved hiking with his family each year in the Rocky Mountains. Winstein was an avid audiophile, hosting "blinded" comparisons in the 1980s between vinyl records and then-new compact discs.

Winstein had a deep interest in film, took silent movies with a hand-cranked, 16-millimeter camera, and founded a film series at the California Institute of Technology while a graduate student. He was proud of having met both Stan Laurel - of Laurel and Hardy, whose films he collected - and Michelangelo Antonioni, the Italian modernist director whom Winstein studied intensely.

He later taught two courses on Antonioni at UChicago's undergraduate College, and he lectured on the director's work at Middlebury College this past fall. "He really appreciated Antonioni's creativity and his use of the medium," said Ted Perry, a Middlebury film scholar and Antonioni specialist, and a friend of Winstein's.

In 1999, Winstein won a Guggenheim Fellowship to collaborate with researchers in cosmology at Princeton University. He began to study the cosmic microwave background radiation - the first flash of light produced after the big bang, now an extraordinarily dim afterglow whose patterns show the footprints of events in the early universe.

Back at Chicago, Winstein helped found the Kavli Institute for Cosmological Physics, where he served as the first director and brought together an interdisciplinary group of physicists and astronomers. He led the QUIET experiment, an international collaboration in Chile's Atacama Desert to measure the polarization, or twists, in the background radiation, to learn the effects of gravity waves believed to have rippled through the fabric of space-time almost 14 billion years ago.

"He had an uncanny ability to motivate people working with him to get more out of them than anyone expected," said Edward Blucher, UChicago's chairman of the Department of Physics.

Bruce Darrell Winstein was born in Los Angeles on Sept. 25, 1943. He attended UCLA before earning his doctorate in physics at California Institute of Technology in 1970.

Winstein was elected to the National Academy of Sciences in 1995 and to the American Academy of Arts & Sciences in 2007. The American Physical Society awarded Winstein and two others the 2007 Panofsky Prize for outstanding achievements in experimental particle physics. In 1976, he gave the inaugural Arthur Holly Compton Lectures, a public lecture series at UChicago. He served on the faculty at Stanford University in 1986.

Winstein is survived by wife Joan, his children Keith and Allison, and his sister Carolee.

A memorial service is planned for the spring. In lieu of flowers, the family requests donations be sent to the Bruce Winstein Fund for Graduate Students, c/o Department of Physics, KPTC 201, University of Chicago, 5720 South Ellis Ave., Chicago, IL 60637.


Related Links:
KICP Members: Bruce D. Winstein

Bruce Winstein, physicist, 1943-2011
Fermilab Today, March 3, 2011
Bruce Winstein
Bruce Winstein
Fermilab Today

Editor's note: Bruce Winstein was heavily involved in work at Fermilab. During the 1990s he led a program at Fermilab of kaon physics experiments, which studied matter-antimatter asymmetries. He received the Panofsky Prize in physics for this work.

Bruce Winstein, an experimental physicist who studied the afterglow of the universe's birth, died Feb. 28 after a four-year battle with cancer. He was 67.

Winstein, the Samuel K. Allison Distinguished Service Professor in Physics, the Enrico Fermi Institute and the College, was known as a punctilious leader of experiments measuring the aftermath of the big bang in two fundamental fields of physics - particle physics and cosmology.

A strong advocate of "blinded" measurements, in which scientists intentionally conceal the final answer while analyzing data to prevent their preconceptions from influencing the result, he imported many practices of particle physics after his mid-career switch into cosmology, the study of the early universe. "Psychologically, it's better," Winstein told an interviewer in 2000. "There's no concern about, 'Do we agree with our old experiment?'"


Related Links:
KICP Members: Bruce D. Winstein

Bruce D. Winstein 1943-2011, University of Chicago physicist, dies at 67
Chicago Tribune, March 6, 2011
by Margaret Ramirez, Chicago Tribune

Bruce Winstein was an experimental physicist at the University of Chicago best known for his ground-breaking research in particle physics and cosmology.

Mr. Winstein, 67, who spent nearly 30 years leading a research team at Fermilab that studied matter and antimatter, the mirror image of the material that makes up the Earth, sun and stars, died of cancer Monday, Feb. 28, in his Oak Park home, according to his wife.

In 1999, Mr. Winstein and his team documented the first evidence that matter and antimatter are not exact mirror opposites. He and his fellow physicists observed a phenomenon called CP violation, or charge parity violation. Their work showed a new way that antimatter follows different rules than regular matter.

Mr. Winstein's finding was hailed as the most significant advancement in understanding the universe's composition since 1964, when Nobel Prize-winning physicist James Cronin discovered CP violation.

In 2007, Mr. Winstein was awarded the Panofsky Prize from the American Physical Society.


Related Links:
KICP Members: Bruce D. Winstein

Astronomer Royal Martin Rees to lecture on mysteries of universe
The University of Chicago News Office, April 7, 2011
Martin Rees, Astronomer Royal
Martin Rees, Astronomer Royal
by Steve Koppes, The University of Chicago News Office

Astronomer Royal Martin Rees will deliver the University of Chicago 2011 Brinson Lecture, titled "From Big Bang to Biospheres," at 6 p.m. Monday, April 11 at the School of the Art Institute of Chicago.

The public is invited to this free event at the MacLean Ballroom, 112 S. Michigan Ave., which is co-sponsored by UChicago and SAIC with support from the Brinson Foundation. Serving as moderator will be Gabriel Spitzer, who covers science, health and the environment for WBEZ radio.

Advanced technology has enabled astronomers to trace cosmic history back to the big bang nearly 14 billion years ago, and begin to understand the emergence of atoms, galaxies, stars and planets, and how life developed a complex biosphere on Earth. In his illustrated lecture, Rees will discuss some of the new questions posed by these advances: What does the long-range future hold? How widespread is life in the cosmos? Is it surprising that physical laws permitted the emergence of complexity? And is physical reality even more extensive than what telescopes can probe?

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The Guardian: 'Martin Rees's Templeton prize may mark a turning point in the "God wars"'

Rees is master of Trinity College, Cambridge and former director of the Institute of Astronomy at Cambridge and of the Royal Society. The author of eight books and many research publications, he has lectured widely in the United States, Europe and the Far East. His research interests include cosmology, galaxy formation, black holes and high-energy phenomena in the universe.

On April 6, Rees accepted the Templeton Prize, which is worth one million British pounds and awarded annually to a scholar or individual who has made "an exceptional contribution to affirming life's spiritual dimension." The Templeton Foundation noted that Rees, who says he has no religious beliefs, has made major contributions to "big questions" in cosmology that have scientific, philosophical and theological implications.

A foreign associate of the U.S. National Academy of Sciences, the Russian Academy of Sciences, the Pontifical Academy of Sciences and several other foreign academies, Rees also is a member of the United Kingdom's House of Lords.


"From Big Bang to Biospheres" with Martin Rees presented by the University of Chicago
WBEZ, April 13, 2011
Brinson Lecture: Martin Rees, Astronomer Royal, From Big Bang to Biospheres
Brinson Lecture: Martin Rees, Astronomer Royal, "From Big Bang to Biospheres"

Listen to the Martin Rees lecture presented by the University of Chicago April 11, 2011

Astronomers have made astonishing progress in probing our cosmic environment thanks to advanced technology. We can trace cosmic history back to some mysterious "beginning" nearly 14 billion years ago. And we understand in outline the emergence of atoms, galaxies, stars, and planets and how, on at least one planet, life developed a complex biosphere of which we are part. But these advances pose new questions: What does the long-range future hold? How widespread is life in our cosmos? Should we be surprised that the physical laws permitted the emergence of complexity? Is physical reality even more extensive than the domain that our telescopes can probe? This lectures addresses (but does not answer!) such questions.

Martin Rees is Master of Trinity College, Cambridge, and holds the honorary title of Astronomer Royal. He was once Director of the Institute of Astronomy at Cambridge and has lectured widely in the U.S., Europe, and the Far East. His research interests include cosmology, galaxy formation, black holes, and "high energy" phenomena in the universe. In addition to his research publications, he is the author of eight books and numerous articles on scientific and general subjects. He is a foreign associate of the U.S. National Academy of Sciences, the Russian Academy of Sciences, the Pontifical Academy, and several other foreign academies. He is a member of the UK's House of Lords and recently completed a five-year term as President of the Royal Society (the UK's national science academy).


Signs of dark matter from Minnesota mine
ScienceNews, May 5, 2011
by Ron Cowen, ScienceNews

An experiment in Minnesota is the first to bolster a long-contested claim that detectors a continent away have found evidence of particles called WIMPs.

WIMPs are theorized particles considered to be leading candidates for dark matter, invisible material believed to make up more than 80 percent of the matter in the universe. In the Minnesota experiment, called COGENT, a hockey puck-sized chunk of germanium deep in a former iron mine attempts to record rare collisions with WIMPS.

In 15 months' worth of data, COGENT researchers detected a seasonal variation in the collision rate - higher in summer and lower in winter - similar to that seen for 13 years by a larger experiment, using different detectors, in Italy. Researchers with that experiment, DAMA/LIBRA, have attributed the results to the Earth's motion through a cloud of WIMPs (for weakly interacting massive particles) (SN: 5/10/08, p. 12). But many physicists have doubted that interpretation because, until now, no other experiment had found similar results.

COGENT team leader Juan Collar of the University of Chicago presented the new findings May 2 in Anaheim, Calif., at a meeting of the American Physical Society. Collar said he would not discuss the results with reporters until after papers describing the work are posted online.

The new COGENT results have features that you would expect from a dark matter detection, "something pretty similar to what DAMA has seen," says theorist Dan Hooper of the Fermi National Accelerator Laboratory in Batavia, Ill., who heard Collar's talk. "Everything that you would hope would be there, if it's dark matter, is basically there."

The finding does not constitute a discovery of dark matter, however, because the likelihood of such results appearing by chance are too high to qualify for what physicists consider proof, notes Hooper.

WIMPs are favored candidates for dark matter particles because they have been predicted in theories attempting to unify nature's known particles and forces. Features predicted for WIMPs correspond with properties expected for cosmic dark matter, the gravitational glue that holds galaxies together and allowed them to form in the first place (SN: 8/28/10, p. 22).

If correct, the COGENT result implies that WIMPs have a relatively low mass, roughly five to 10 times the mass of a proton, says Katherine Freese of the University of Michigan in Ann Arbor. Recent results from other experiments appear to be in conflict with the experiment but may not be as sensitive as COGENT is to collisions with such low-mass particles (SN: 5/7/11, p. 12).

The COGENT finding intrigues Freese, who, with other researchers, predicted in the 1980s that a seasonal variation could be a sign of dark matter. That idea envisions vast halos of WIMPs engulfing galaxies, including the Milky Way. Earth would plow through the Milky Way's WIMP halo faster in summer than winter because its revolution around the sun would then correspond with the rotation of the galaxy into the WIMP halo. In winter, the Earth's revolution would take it in the opposite direction of the galaxy's rotation. So detectors ought to see more collisions in summer than winter - the trend now seen by both DAMA/LIBRA and COGENT.

Theorist Neal Weiner of New York University says his calculations indicate that the COGENT team was either very lucky or saw an unusually high variation in the collision rate to be able to make a tentative detection with just 15 months of data.

Theorists are now increasingly challenged to identify properties of dark matter that might explain why some experiments see signs of the particles while others do not, Weiner said May 2 in Baltimore at a meeting on dark matter.


Related Links:
KICP Members: Juan I. Collar; Daniel Hooper
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)

Second experiment hints at seasonal dark matter signal
NewScientist, May 6, 2011
The Soudan mine is home to the CoGeNT experiment
The Soudan mine is home to the CoGeNT experiment
by Valerie Jamieson, NewScientist

Things just got a little less lonely for researchers who have been insisting for years not only that their experiment has found dark matter, but also that the dark matter signal varies with the seasons. Now a second experiment, called CoGeNT, is reporting similar findings, though both results are in conflict with two other teams' observations.

No one knows what dark matter is - astronomers merely detect its gravitational pull on normal matter, which it seems to outweigh by a factor of five to one. But many researchers believe it is made of theoretical particles called WIMPs, which interact only weakly with normal matter.

Since 1998, researchers running the DAMA experiment deep inside the Gran Sasso mountain in Italy have claimed to have found evidence of WIMPs.

DAMA uses an array of sodium iodide detectors to spot the rare moments when WIMPs slam into atoms in the detectors, producing flashes of light. The number of flashes ebbs and flows with the seasons, and DAMA team members argue that this is because Earth's velocity relative to the surrounding sea of dark matter changes as the planet orbits the sun. They say their observations could be explained by a WIMP weighing a few gigaelectronvolts.

Tense situation
However two other experiments have found no sign of dark matter with their detectors. One, called XENON100, uses 100 kilograms of liquid xenon deep below Gran Sasso mountain, and the other, called CDMS II, uses ultra-pure crystals of germanium and silicon housed in a deep mine in Soudan, Minnesota.

Both experiments are so sensitive that they should have seen dark matter if the DAMA result is due to WIMPs. "The situation has created tension," says Dan Hooper, a theorist at the University of Chicago in Illinois.

Now another dark matter experiment called CoGeNT has found a seasonal variation in its results, reports team leader Juan Collar, who presented an analysis of 442 days of observations at the American Physical Society meeting in Anaheim, California, on Monday.

"We tried like everyone else to shut down DAMA, but what happened was slightly different," Collar said during his presentation.

Germanium crystal
The CoGeNT detector is tiny compared with many other dark matter experiments. It comprises a 440-gram crystal of germanium. Still, dark matter is so abundant that 100 million particles of it are expected to pass through the CoGeNT detector every second.

About once a day, one of these will wallop a germanium nucleus, sending the nucleus careering through the crystal, where it rips electrons from neighbouring atoms. An electric field sweeps these electrons towards an electrode to produce a tiny electrical signal.

Previously, the CoGeNT team reported an excess of events when it ran its experiment in the Soudan mine for 56 days (Physical Review Letters, DOI: 10.1103/PhysRevLett.106.131301). Team members said the excess could be due to some kind of background noise that physicists don't understand, or potentially to WIMPs weighing 7 GeV.

'Smoking gun'?
The experiment kept running continuously until a fire in the Soudan mine on 17 March halted observations. This motivated Collar and his colleagues to look for a seasonal variation in the 442 days of observations they had already collected. "I hope this isn't the final data we have taken," says Collar, who has not yet been allowed to return to the Soudan mine to check for damage.

The CoGeNT team finds that their signal changes with the seasons in exactly the same way as the DAMA result does. And it is consistent with a low-mass dark matter particle, like that reported by DAMA.

"The annual modulation is the closest thing to a smoking gun [for dark matter]," says theorist Jonathan Feng at the University of California, Irvine, who is not part of the CoGeNT team. "This is the first evidence we've seen it somewhere other than DAMA."

Weird WIMP
But Laura Baudis at the University of Zurich in Switzerland, who reported at the meeting on Monday that XENON100 still had seen no signs of dark matter, is not sure what to make of the results: "I need time to think about them."

Feng suggests that the discrepancy among all the experimental results may simply be due to the assumption that WIMPs interact the same way with protons and neutrons. If this is not the case, that could explain differences in the signals from xenon and germanium detectors, which each have a different ratio of protons to neutrons ( "These experiments may look inconsistent, but a small theoretical tweak can bring everything in to line," he told New Scientist.

Both the CoGeNT and XENON100 teams are planning to enlarge their experiments. Approval has just been given to build the XENON1T experiment in the Gran Sasso mine, which will use 1 tonne of liquid xenon. And the CoGeNT team is planning to replace its single germanium crystal with four separate crystals, each weighing 1 kilogram, starting later this year.


Related Links:
KICP Members: Juan I. Collar; Daniel Hooper
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)

Award-winning teachers find the unexpected
The University of Chicago News Office, May 27, 2011
Angela Olinto, KICP senior member  <i>Photo credit: Dan Dry</i>
Angela Olinto, KICP senior member

Photo credit: Dan Dry
by Steve Koppes, The University of Chicago News Office

When Angela Olinto communicates with other cosmologists, they often rely on equations to transmit their scientific thoughts quickly. But teaching cosmology to undergraduate non-science majors requires completely different methods.

It challenges your imagination," says Olinto.

"We have the saying that we teach teachers. We learn a lot from these future teachers. We're actually teaching and learning pretty much at the same rate." - Angela Olinto

The Department of Astronomy & Astrophysics does not offer an undergraduate major but provides a variety of service courses for undergraduates who wish to learn about the universe. Olinto has been significantly involved in organizing and teaching these courses.

Cosmology for non-science majors
In 1998, she helped redesign the department's classes for undergraduates from non-science majors. The following year, she helped develop the department's specialization in astrophysics for science majors.

Then in 2008, Olinto helped develop a sequence of three study-abroad courses in astronomy and astrophysics at the University of Chicago Center in Paris. Olinto recently returned from Paris, where she had been teaching a course titled "The Origin of the Universe and How We Know It."

That course is for non-science majors, as are her courses on the "Origin and Evolution of the Universe" and on "European Astronomy & Astrophysics." For science majors, Olinto also has taught the Physics of the Early Universe and the Physics of Galaxies in the Universe.

"These were all new classes, actually, every single one of them," she says.

Olinto approaches the teaching of cosmology to non-science majors with the idea that "everybody should be able to get some of it and that curiosity is really the requirement more than the mathematical skills."

Related Links:
KICP Members: Angela V. Olinto

The Hunt for Dark Matter in the Universe
Kavli Foundation, June 2, 2011
Juan Collar (Credit: Dan Dry, The University of Chicago)
Juan Collar (Credit: Dan Dry, The University of Chicago)
Kavli Foundation

KICP's Juan Collar leads a team that detected a signal compatible with dark matter theory. In an interview, he discusses the significance of the finding, what will be needed to prove the existence of dark matter, and how turning to an old technology is helping scientists in the 21st Century.

A DARK MATTER DETECTOR about 700 meters below the ground in a Minnesota mine has recorded a seasonal modulation in staggeringly faint electrical pulses - the possible result of dark matter particles called WIMPs that envelope the Milky Way galaxy and collide with atoms in the detector's germanium crystal.

The finding, by the Coherent Germanium Neutrino Technology, or CoGeNT] experiment at the Soudan mine, is described in a paper posted online by a team of researchers led by Juan Collar of the Kavli Institute for Cosmological Physics (KICP) at the University of Chicago.

The results are consistent with the modulation in signals first recorded more than a decade ago by the DArk MAtter/Large sodium Iodide Bulk for RAre processes (DAMA/LIBRA) experiment at Gran Sasso, Italy. It also appears to match recent but as-yet-unpublished findings by another experiment called CRESST, or the Cryogenic Rare Event Search with Superconducting Thermometers, also at Gran Sasso.

Collar said his experiment is carefully designed to detect the collisions between WIMPs (Weakly Interacting Massive Particles, which are hypothesized by dark matter theory) and atoms in the crystal. "It's sensitive to very low energies, and that's where we got stuck," Collar said of CoGeNT's detection of a modulation in signals. "We're seeing something down there that we don't quite understand yet."

Collar and his colleagues, who have submitted the paper "Search for an Annual Modulation in a P-type Point Contact Germanium Dark Matter Detector" for publication, emphasized that the origin of the signals is unknown, but that the data collected from 442 days of observations "are prima facie congruent when the WIMP hypothesis is examined."

Collar discussed his research, and the meaning of his recent findings, in a conversation with The Kavli Foundation.

THE KAVLI FOUNDATION (TKF): Is your tentative result, which suggests a seasonal variation in the number of particle collisions with the nuclei in your detector, evidence for WIMPs - that is, evidence for dark matter?

JUAN COLLAR: You know, evidence is a big word in particle physics. In principle, one might be tempted to speak the language of evidence, but this whole situation with dark matter is so volatile one must be very cautious. We decided to share our data and publish. The impact is rather large, because our observations seem to agree with what DAMA has seen for about 10 years now. They are also similar to preliminary results from CRESST, another dark matter experiment.

So it's an important result. But evidence? We wouldn't touch that word with a ten-foot pole. There is evidence, perhaps, for a modulation in the data. But for the detection of dark matter? That is something that we've stated DAMA shouldn't claim, even after 10 years of very solid observation of a modulation. The origin of this modulation does not necessarily have to be dark matter particles.

TKF: What is unique about your detector in the CoGeNT experiment, and what exactly is it detecting?

COLLAR: When a dark matter particle, a WIMP, strikes the nucleus of an atom in a germanium crystal, the nucleus recoils, striking other nearby atoms and knocking off their electrons. Our detector reads this ionization as an electrical signal. What's special about our detector is that it's optimized to look for light-mass dark matter particles, arguably the best for that particular job.

The reason for this is that most other detectors are designed to detect particles about 100 times the mass of a proton. But if WIMPS are much lighter than that, say just a few times the mass of a proton, then you need a detector with very low electronic noise. You have to be able to distinguish the very tiny energy depositions that are triggered by these collisions, because that's what you expect from lighter particles; they don't pack as much of a punch as something heavier.

That's what CoGeNT detectors are designed for, and that's where they perform very well, dramatically so. They are sensitive to very low energies, and that's where we got stuck. We're observing something down there that we don't quite understand yet. We cannot yet tell you what it is, but of course we can list many possibilities. The low energy events that we end up with - we don't see anything anomalous in them. They look like they're produced by some form of radiation.

TKF: You detected a seasonal modulation in your data after 442 days of observations, and then your experiment was halted in March by a fire in the Soudan mine. Was the CoGeNT detector damaged? If it's OK, will you continue to gather more data to strengthen your result?

COLLAR: It's a pure coincidence, but we started at the expected time for the minimum number of expected WIMP collisions. We started early in December of 2009, that is, we departed from the minimum, went through a full cycle, and on the way into the second cycle we ran out of luck. There was this fire in the mine shaft, and that stopped everything.

We were to some extent lucky. The underground laboratory is pretty large, and our side was untouched by either fire or fire-extinguishing fluid. That's what made much of the mess down there; so much foam had to be injected that it actually pushed the doors open to the laboratory and some experiments were completely covered by it. Our experiment was fine; but the detector went through a thermal cycle. Normally, we keep these devices at ninety degrees Kelvin, which is pretty chilly, and when you warm them up like this the quality of the vacuum inside the detector makes a critical difference. If it's a good vacuum, you should be fine when you turn it on again; if it's a bad vacuum, the detector could be useless for the delicate work we are trying to do. This is why we have analyzed the data collected up until the fire. We have 15 months of observations and we don't know if we'll have another day of good data with this device.

If this detector is not dead and the signal rate starts to decrease again toward next December and then picks up again afterward - the chances of seeing something like that start to become very small, very fast. The opposite side of the coin is, of course, if it doesn't do what I just described. In that case, the modulation we have observed so far may have been just a fluke.

TKF: One possibility is that you're seeing a systematic error, that is, false signals that originate from the detector itself. But if CoGeNT, DAMA and CRESST - all different experiments with different kinds of detectors and different methods - are seeing the same seasonal modulation in collisions, isn't it unlikely that the signal is some kind of systematic effect?

COLLAR: Indeed. Yes, you're right. The targets, or the material that the detectors are made of, are different. Also, each of these experiments collects and reads events differently.

"[It] gives you pause, the fact that the same kind of dark matter particle could be behind these three different observations from three very different detectors."

In our detector, particles strike the germanium crystal and produce ionization. In DAMA, particles strike sodium iodine, which is a scintillator material that generates light when radiation impinges on it, and that light is read out by a photomultiplier - an electronic eye of sorts - that turns light into electrical pulses. CRESST, meanwhile, is entirely different. CRESST uses a calcium tungstenate crystal, another scintillating material, but it is also operated as another type of detector called a bolometer, in this case, a hybrid bolometer. It's a device where they read out the light that is produced through scintillation, but also the increase in temperature that is produced by the particle interaction.

So you're perfectly right, it's kind of suspicious that what these three experiments observe can be interpreted as a dark matter particle in common, of the same mass and with the same probability of interaction with different detector materials. That gives you pause, the fact that the same kind of dark matter particle could be behind these three different observations from three very different detectors.

TKF: The CRESST experiment appears to be seeing signals compatible with dark matter. What makes them confident that they are seeing something similar to what CoGeNT is seeing?

COLLAR: They've been exquisitely careful about trying to eliminate other possibilities. Over the last year or so, they have implemented different precautions, and have made different tests of their detector - all to exclude the possibility that what they're observing is a number of possible sources of background radiation. They've been discarding those one after another, and they're now left with about 20 events that they just don't know what to make of. They look like nuclear recoils, particularly affecting the oxygen in the crystal, and they cannot be explained away. They see evidence for 20 events that might be compatible with the same particle that might be producing a modulation in DAMA, or might be producing a modulation in our detector.

TKF: So, because the chance is very tiny that this is some background noise, the odds are higher that these collisions are being caused by dark matter particles, is that correct?

COLLAR: Well, that's not entirely true. The first part of the statement is correct. You can grow convinced that the chances are small that this is due to a background or any other non-exotic process that we can dream up. But it takes a leap of faith to go from there to the next step, claiming that what we are detecting is dark matter. That is actually why the community has been very critical of DAMA. They claim that the chances are tremendously small that their fluctuation is due to some kind of fluke. True. But going from there to stating, ergo it must be dark matter - that's a hard call. But the DAMA collaboration seems not to be detoured by such considerations.

TKF: Could this modulation in collisions also be due to some kind of exotic physics that we don't yet know about?

COLLAR: Well, exactly. It could be. It's one of three things: It's either dark matter, or it is something perfectly boring, systematic and instrumental - it wouldn't be the first time in physics that we fool ourselves into thinking that something mundane is relevant. This sort of situation typically happens when agreement with other experiments is noticed, and soon after you are obsessed with observations that normally you wouldn't pay any attention to.

Or third, it might be something interesting that's not related to dark matter. For instance, we could be noticing new effects arising from solar neutrino interactions in the detectors, as some phenomenologists are proposing. That would be pretty exciting, a new piece of physics not really related to dark matter. We'd still get to learn something about nature. Of course, the first possibility to consider is some instrumental effect that we have not figured out yet.

TKF: DAMA has claimed that they've also detected a seasonal modulation in their data, but other projects such as CDMS-II claim that they are not seeing compatibility with this modulation signal. What do you make of that?

COLLAR: CDMS-II is observing a spectrum of irreducible signals. That is, they've tried their best to reject them but they still remain, and they have essentially the same energy spectrum as ours. The material of their detector is also the same as ours - germanium.

CDMS can only marginally exclude what we are observing, and that is after much trying. I claim that they are not doing an unbiased job, and that they're neglecting important facts. I don't see any contradictions between CDMS-II data and ours. To the contrary, there is quite a good chance that there might be a lot in common between our data and theirs.

TKF: You've been involved in other experiments to detect dark matter particles - namely COUPP, the Chicagoland Observatory for Underground Particle Physics at Fermi National Laboratory. This experiment uses a quartz bell jar or bubble chamber as a detector for WIMPs. But this type of detector was conceived by physicist Donald Glaser in 1952. Why turn to an old technology in the 21st century race to detect dark matter?

The old saying "There's nothing new under the sky" actually applies remarkably well to the field of radiation detection. There are only so many ways you can detect radiation, and we seem to have gone through most of them. If you look at the history of our field, there have been very few important additions to the repertoire of radiation detectors in the last 30 or 40 years. There are instead a lot of variations around the same themes.

I started working with superheated liquids at the University of Paris. In my case, contact was purely coincidental. I was working on something unrelated to dark matter when I ran into a paper in a journal called Health Physics. They were talking about radiation dosimeters used to monitor neutron dose in hospitals, while being extremely insensitive to gamma radiation. I thought, "That sounds like a WIMP detector". I went to my boss in Paris, Georges Waysand, and asked, "What's going on with these detectors?" and he said, "I have no idea." So we decided to look into them. When I came to Chicago we moved to using the same concept in the form of bubble chambers.

"The old saying "There's nothing new under the sky" actually applies remarkably well to the field of radiation detection. There are only so many ways you can detect radiation, and we seem to have gone through most of them."

Let me explain something that is unique about the bubble chamber. In DAMA and CoGeNT, at the end of the day we are dealing with electrical pulses. In DAMA you have a flash of light that is invisible to the eye, and there's a photomultiplier that converts it and amplifies it into a small current. All these things are happening very, very close to the electronic noise in these devices. In CoGeNT, it's the same story. We pull the ionization signal out of the crystal and we amplify it. This is done close to the noise of the detector.

But a bubble is a bubble is a bubble. If you started to see an annual modulation in the rate of something that at the end of the day is macroscopic and can be detected via standard photography, there's no concern that there's some electronic noise or anything similar conspiring to give you signals you may mistake for a WIMP.

The whole beauty of the bubble chamber is that it all starts with the microscopic process of radiation interacting with matter. And you don't have to move a finger to amplify it. It's all coming from the fact that the liquid is out of equilibrium. It's an unstable system, and when an episode of microscopic boiling happens because a particle interacted with the fluid, everything that ensues, the formation of visible bubbles, is a spontaneous transition from the microscopic world to macroscopic observables. You don't have to amplify small signals through noisy chains of electronics or anything like it.

TKF: In bubble chamber detectors, WIMP collisions are expected to generate a single bubble, while other, more energetic particles are expected to trigger bubble tracks. Why is that?

COLLAR: When a WIMP strikes a nucleus, that nucleus doesn't go very far at all, whether the detector medium is a liquid or a solid. The distance is of the order of hundreds of angstroms, and not much more. The reason is that the nuclear recoil is pretty heavy. The nucleus slows down rapidly; it bangs around a lot and hits a lot of other nuclei, and it dissipates its energy very, very fast over a very short distance.

That's why when a nuclear recoil happens in a bubble chamber liquid, it produces a seed of nucleation, an episode of very local, microscopically localized high temperature, caused by this nucleus bouncing around and hitting other nuclei. If you were able to stick a thermometer at the point of interaction, it would measure an effective temperature in the hundreds or thousands of degrees.

Under some conditions, you can create a microscopic bubble. Those conditions are met for nuclear recoils because the local heating is very high, precisely because the nucleus doesn't go very far. The recoil track is very short. But for other types of radiation, the energy is deposited over much longer distances. It's the same amount of energy, but it is spread out, and the particle doesn't heat up the liquid enough locally to produce bubbles. We fine-tune the temperature and pressure of the bubble chamber to be able to detect only bubbles produced by nuclear recoils like those expected from WIMPs, and not the tracks produced by uninteresting known particles.

We catch the bubbles in the act of forming when they are smaller than 1 millimeter. We take short movies, examining the frames in real time every ten milliseconds. The software is looking for a change in the image; essentially you have a motion sensor going, so you catch them as they grow. When you have confirmation that an image change is large enough to be a bubble, then you immediately recompress the liquid so that the whole volume doesn't boil, and you end up with a little movie covering a fraction of a second. In those you can see these bubbles start to grow, start to ascend through the fluid and then shrink back as we recompress the fluid. And then they disappear.

TKF: Getting back to the CoGeNT experiment, now that you've made public this result, what is the next step for you in the search for dark matter?

COLLAR: For about a year now, we've been designing the next generation of CoGeNT detectors, and hopefully they will have lower background noise and an improved ability to perceive smaller signals.

TKF: Is this the same detector model used by CoGeNT, with germanium crystals?

COLLAR: This is the same detector concept, but with a lot of improvements. It's essentially the same thing, but hopefully even better in performance.

TKF: What are your plans for continued studies with bubble chambers?

COLLAR: The bubble chamber, in principle, should allow us to test this hypothesis - that there should be a modulation in the rate of collisions between WIMPs and the nuclei in our detectors. We can make our bubble chamber sensitive to light WIMPs, and we have done that before. We have operated the chamber in conditions where we should be able to see the bubbles produced by these particles - if they exist.

The problem is that there are internal sources of neutrons in our bubble chamber. Some materials inside the bubble chamber are generating - at a very small rate - a neutron every so often. And we have evidence for that, because we see events containing multiple bubbles that can only be neutrons.

We identified where these neutrons are coming from, and we're going to replace those parts of the detector this summer - these sources of internal neutrons in the bubble chamber. After that, we'll attempt to look for light WIMPs with our bubble chambers.

TKF: What are the sources of these internal neutrons inside the bubble chamber?

COLLAR: In this particular case, they seem to be dominated by our ceramic piezos - they are electronic sensors that we use to detect the acoustic emission that accompanies the production of the bubbles. When bubbles form, it's a rather dramatic process. You have a liquid that is out of equilibrium. It's super-heated, so it's a liquid that you've tricked into remaining a liquid when it should be a gas at the pressure and temperature you've set.

So, when a bubble forms, it yields quite a release of energy. The bubble expands very fast, and this produces a cracking sound that was described as a "plink" by the inventor of the bubble chamber many years ago - (in 1952, by physicist Donald Glaser at the University of Michigan). He actually used phonograph pickups to detect that sound in bubble chamber prototypes and trigger their photography. In our case, the sound is detected through the ceramic piezo-electric sensors, and we found out that there is enough uranium and thorium in them to produce these neutrons at a very, very low rate. We are getting a neutron essentially every week, and these neutrons start close enough to the active part of the chamber to give us some bubbles.

These piezos have to be replaced, and we already know how to do this. We found better ways to produce those ceramics. There are some inspection windows that need to be replaced as well. Those are the two main sources of internal neutrons that we could find. Everything else we think should be fine as it is.

TKF: So as long as you are eliminating all the known sources of noise, such as the ceramic material that you've identified in your bubble chamber, then hopefully what you're left with is an authentic signal of WIMPs, of dark matter?

COLLAR: Well...

TKF: That would be a leap of logic.

COLLAR: That would be a leap of faith. You would be left wondering, in the case of the bubble chamber, if you have rejected all the possibilities that your signals might be something else - for instance, some other background radiation.

"I'm going to quote my colleague here in Chicago, (astrophysicist) Rocky Kolb. Rocky says, 'It's going to take a village to discover dark matter,' and I agree with that. It's going to take more than the direct detection community observing these recoils."

Now, a few months ago, when the signals we have now identified to be these neutrons produced inside the chamber started to show, we had been pretty convinced that we hadn't missed anything. We thought, "These must be WIMPS". And then we saw a triple bubble, which a WIMP cannot produce. WIMPS cannot interact more than once. You're lucky enough to get them to interact at all.

We immediately knew we had this neutron problem, and within a few weeks we knew where they had to be coming from. We measured the radioactivity in the piezos and other materials, and found agreement with the rate of neutron production. We explained away the observed signal.

There is a lesson to be learned there. It teaches you that, not only for bubble chambers but any other WIMP detector, after you clean things up you're always going to be left wondering what else it is that you missed. Particle physics and in particular dark matter searches can be very tricky.

TKF: Another approach on the road toward detecting WIMPs, besides measuring the seasonal modulation, is to measure the direction that a nuclei recoils after a particle collides with it - and the modulation in the direction of recoil over time. That's because according to dark matter theory, WIMPs are expected to strike the Earth from a particular direction in the sky, depending on the time of the day. How far are we from making this kind of measurement, and would it provide stronger evidence for dark matter?

COLLAR: That's actually a technology that nobody has yet - a technology that can see the direction of the recoil. There are small prototypes that researchers have been building, and it is an extremely promising technique.

What we're noticing is just a modulation in the rate of collisions, and that's a lot less complex than detecting a modulation in the direction of the recoil. So right now, what we and everyone else who is trying to detect dark matter have available is technology to look for this annual modulation in rate. That's a poor man's smoking gun, unfortunately.

The day someone observes the modulation in the direction of the recoils - that would be very hard to mimic, and it would be the next step on the road to a discovery. It would be very hard to explain such data as anything else other than dark matter, because there's essentially nothing else in nature that could imitate that.

The problem is that the only way that we know how to spot the direction of a recoil is by stretching the short tracks they make in a solid. They only span on the order of 500 angstroms, so there's no way we could image that in a radiation detector. The solution, then, is to rarify the detector medium, to move to gaseous detectors and to operate them at very low pressure. Then, those tracks - those little tracks that the recoils might produce with a preferred direction if they're coming from WIMPS - they can be stretched to a few millimeters. We have the technologies to image that - barely, but we do.

So, the challenge is that your detector has to use targets that have a very low mass because their density has to be very, very small. At the same time, the detectors must have enough overall mass in order to interact with incoming WIMPs, which have, by definition, a very low probability of striking. And then you end up with enormous devices at a very high cost. One day we may be able to observe this beautiful WIMP signature, but right now the detectors are just small prototypes.

TKF: Let's say eventually you are able to confirm this seasonal modulation in collisions with CoGeNT and with COUPP, and other different experiments show the same thing. And then the day arrives when we can measure the direction of recoils, and we detect a daily modulation in the direction of recoils.

If all these results are replicated with different experiments around the world, which use different materials and different methods, would you feel confident that we have detected WIMPs - that is, dark matter?

COLLAR: I'm going to quote my colleague here in Chicago, (astrophysicist) Rocky Kolb. Rocky says, "It's going to take a village to discover dark matter," and I agree with that. It's going to take more than the direct detection community observing these recoils. Certainly the directional signature would be fantastic, but I think we're really far away from getting to that point, if we ever get to that point.

If several experiments of our kind detect the same modulation, that would be tremendous. But personally, I believe you even need a bit more than that. And what else is that little extra?

Well, accelerator experiments are in principle sensitive to the same types of particles that we're searching. If you can produce man-made WIMPs in accelerator experiments, and they match the properties that we observe in our experiments, that would be fantastic.

On top of anything that the detection community might find, there's a theoretical framework that explains why these particles exist, why they have the mass they have, the probability of interaction that we observe in experiments, etc. This theoretical framework also generates new predictions that you can go out and test.

If those theories are confirmed, at that point, we could say that we did it.

TKF: What are the perils of relying solely on direct detection experiments, without returning to theory to check on what you are seeing?

COLLAR: The problem with just relying on direct detection experiments is the following: we are biased. For instance, we are paying attention to these light WIMPs, but why? Because they are really almost the only thing left that could explain DAMA's observations. Everything else seems to be excluded, so you start to pay a lot of attention to those.

Now, maybe the CRESST guys are paying more attention to those 20 events than they should, because they're biased by DAMA's pre-existing results. Same exact thing applies to us and our modulation within CoGeNT. So on and so forth.

There have been plenty episodes in the history of particle physics where a number of experiments have observed the same thing, and then years later an equally large number of experiments found nothing. And in some instances, there was never a good explanation as to why the first batch of experiments saw anything at all in the first place.

You know, things come and go. A few years ago, physicists thought they were observing nuclear structures containing five quarks, the so-called pentaquarks. Eleven experiments had pretty good solid evidence for them, and then many more experiments came along and saw nothing. And now the interest is pretty much dead.

Nobody knows what happened there. We do not have a good explanation as to why these objects were observed in the first place. The evidence just went away. So that's why you should not rely exclusively on direct detection experiments for dark matter, in my opinion.

I am much more conservative than many of my colleagues. Some will tell you that their experiment, on its own, is going to find dark matter, with absolute certainty. Crazy as that sounds.


Related Links:
KICP Members: Juan I. Collar; Edward W. Kolb
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT); COUPP/PICO

New data still have scientists in dark over dark matter
The University of Chicago News Office, June 6, 2011
KICP physicist Juan Collar (left) and University of Washington graduate student Mike Marino inspect the CoGeNT experiment at the Soudan Mine in Minnesota. CoGeNT has detected a seasonal signal variation during its first year of operation. This is what scientists would expect if dark matter is made of Weakly Interacting Massive Particles (WIMPs), but the CoGeNT collaboration considers the results to be inconclusive.  <i>Image Credit: Courtesy of CoGeNT Collaboration</i>
KICP physicist Juan Collar (left) and University of Washington graduate student Mike Marino inspect the CoGeNT experiment at the Soudan Mine in Minnesota. CoGeNT has detected a seasonal signal variation during its first year of operation. This is what scientists would expect if dark matter is made of Weakly Interacting Massive Particles (WIMPs), but the CoGeNT collaboration considers the results to be inconclusive.

Image Credit: Courtesy of CoGeNT Collaboration
by Steve Koppes, The University of Chicago News Office

A dark-matter experiment deep in the Soudan mine of Minnesota now has detected a seasonal signal variation similar to one an Italian experiment has been reporting for more than a decade.

The new seasonal variation, recorded by the Coherent Germanium Neutrino Technology (CoGeNT) experiment, is exactly what theoreticians had predicted if dark matter turned out to be what physicists call Weakly Interacting Massive Particles (WIMPs).

"We cannot call this a WIMP signal. It's just what you might expect from it," said Juan Collar, associate professor in physics at the University of Chicago. Collar and John Orrell of Pacific Northwest National Laboratory, who lead the CoGeNT collaboration, are submitting their results in two papers to Physical Review Letters.

WIMPS might have caused the signal variation, but it also might be a random fluctuation, a false reading sparked by the experimental apparatus itself or even some exotic new phenomenon in atomic physics, Collar said.

Dark matter accounts for nearly 90 percent of all matter in the universe, yet its identity remains one of the biggest mysteries of modern science. Although dark matter is invisible to telescopes, astronomers know it is there from the gravitational influence it exerts over galaxies.

Theorists had predicted that dark matter experiments would detect an annual modulation because of the relative motion of the Earth and sun with respect to the plane of the Milky Way galaxy.

The sun moves in the plane of the galaxy on the outskirts of one of its spiral arms at a speed of 220 kilometers per second (136 miles per second). The Earth orbits the sun at 15 kilometers per second (18.5 miles per second). During winter, Earth moves in roughly the opposite direction of the sun's movement through the galaxy, but during summer, their motion becomes nearly aligned in the same direction. This alignment increases Earth's net velocity through a galactic halo of dark matter particles, whose existence scientists have inferred from numerous astronomical observations.

Like a cloud of gnats
WIMPs would be moving in random directions in this halo, at velocities similar to the sun's. "You find yourself in a situation similar to a car moving through a cloud of gnats," Collar explained. "The faster the car goes, the more gnats will hit the front windshield."

CoGeNT seems to have detected an average of one WIMP particle interaction per day throughout its 15 months of operation, with a seasonal variation of approximately 16 percent. Energy measurements are consistent with a WIMP mass of approximately 6 to 10 times the mass of a proton.

These results could be consistent with those of the Italian DArk MAtter (DAMA) experiment, which has detected a seasonal modulation for years. "We are in the very unfortunate situation where you cannot tell if we are barely excluding DAMA or barely in agreement. We have to clarify that," Collar said.

In particle physics, he further cautioned, agreement between two or three experiments doesn't necessarily mean much. The pentaquark is a case in point. Early this century, approximately 10 experiments found hints of evidence for the pentaquark, a particle consisting of five quarks, when no other known particle had more than three. But as time went on, new experiments were unable to see it.

"It's just incredible," said UChicago physics Professor Jonathan Rosner. "People still speculate on whether it's real."

Collar and his colleagues have calculated the probability that their finding is a fluke to be five-tenths of a percent, or 2.8 sigma in particle physics parlance.

"It's not an exact science yet, unfortunately," Collar said. "But with the information we have, the usual set of assumptions that we make about the halo and these particles, their behavior in this halo, things seem to be what you would expect."

Other dark-matter experiments, including Xenon100, have not detected the seasonal signal that CoGeNT and DAMA have reported.

"If you really wanted to see an effect, you could argue that the Xenon100 people don't have the sensitivity to Juan's result," said Rosner, who is not a member of the CoGeNT collaboration. "On the other hand, they've done a number of studies of what their sensitivity is at low energies and they believe they're excluding this result."

Interrupted by fire
CoGeNT operated from December 2009 until interrupted by a fire in the Soudan mine in March 2011. Fifteen months of data collection is a relatively brief period for a dark-matter experiment. In fact, Collar and his colleagues decided to examine the data now only because the fire had stopped the experiment, at least temporarily.

The fire did not directly affect the experiment, but the CoGeNT team has not been able to examine the detector because of clean-up efforts. The detector may no longer work, or if it does work, it may now have different properties.

"This effect that we're seeing is touch-and-go. It's something where you have to keep the detector exquisitely stable," Collar said. If a single key characteristic of the detector has changed, such as its electronic noise, "We may be unable to look for this modulation with it from now on."

The putative mass of the WIMP particles that CoGeNT possibly has detected ranges from six to 10 billion electron volts, or approximately seven times the mass of a proton. "To look for WIMPs 10 times heavier is hard enough. If they're this light, it becomes a nightmare," Collar said.


Related Links:
KICP Members: Juan I. Collar; Jonathan L. Rosner
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)

Cosmologist Josh Frieman to present June 9 lecture on 'The Dark Universe'
The University of Chicago News Office, June 8, 2011
Josh Frieman, KICP senior member.
Josh Frieman, KICP senior member.
by Steve Koppes, The University of Chicago News Office

Josh Frieman, director of the international Dark Energy Survey collaboration, will kick off a new lecture series on current astrophysics with a talk on "The Dark Universe" at 7 p.m. Thursday, June 9 at the Adler Planetarium, 1300 S. Lake Shore Drive in Chicago.

Over the last decade, cosmologists have discovered that only 4 percent of the universe is made of ordinary matter - the atoms and molecules that form stars, planets and people. The other 96 percent is dark, existing in a form totally unlike anything scientists have ever encountered.

Dark matter, which makes up approximately a quarter of the universe, holds galaxies together and is the key ingredient in their formation. The remaining three-quarters of the universe is composed of dark energy, a mysterious force that is causing the expansion of the universe to speed up.

Frieman's presentation will introduce "The Dark Universe," review what scientists have learned about it and describe new experiments and observatories that aim to solve the enigmas of dark matter and dark energy. The presentation will include a virtual full-dome tour of the large-scale universe recently revealed by cosmic sky surveys.

Frieman is a professor in astronomy & astrophysics at the University of Chicago and a senior staff scientist at Fermi National Accelerator Laboratory's Center for Particle Astrophysics. He directs the Dark Energy Survey, a collaboration of more than 120 scientists from 20 institutions on three continents. The collaboration is building a 570-megapixel camera for a telescope in Chile to probe the origin of cosmic acceleration.

Admission is $10 general admission, $5 for Adler members and students. For more information, visit


Related Links:
KICP Members: Joshua A. Frieman
Scientific projects: Dark Energy Survey (DES)

President Obama Meets U.S. Laureates of 2010 Kavli Prizes
Kavli Foundation, June 11, 2011
President Barack Obama talks with U.S. recipients of the 2010 Kavli Prize in the Oval Office, June 6, 2011.   <i>Official White House Photo by Pete Souza</i>
President Barack Obama talks with U.S. recipients of the 2010 Kavli Prize in the Oval Office, June 6, 2011.

Official White House Photo by Pete Souza
Kavli Foundation

June 6, 2011

At the White House today, President Barack Obama met in the Oval Office with the seven U.S. recipients of the 2010 Kavli Prizes to recognize and honor their seminal contributions to the three fields for which the Prizes are awarded -- astrophysics, nanoscience and neuroscience.

Joined by the President's science advisor, John P. Holdren, President Obama greeted Kavli Prize Laureates Roger Angel (University of Arizona), Jerry E. Nelson (University of California, Santa Cruz), Donald M. Eigler (IBM Almaden Research Center), James E. Rothman (Yale University), Richard H. Scheller (Genentech), Nadrian C. Seeman (New York University), and Thomas C. Sudhof (Stanford University). Accompanying the laureates were Fred Kavli, Founder and Chairman of The Kavli Foundation; Robert W. Conn, President of The Kavli Foundation; and Wegger Chr. Strommen, the Norwegian Ambassador to the United States.

The Kavli Prizes are a partnership between The Kavli Foundation (U.S.), the Norwegian Academy of Science and Letters and the Norwegian Ministry of Education and Research.

"We are extremely grateful to the President for the honor of this visit, and for his strong and heartfelt commitment to scientific research and discovery," said Fred Kavli. "It reflects the nation's deep support for innovative research that scientists across the country rely upon, including the foundational research discoveries of the 2010 Kavli Laureates."

The Kavli Laureates received their awards for research that made it possible to look more deeply and clearly into the universe, to control matter on the nano scale, and to understand how the brain's nerve cells communicate.

The 2010 Kavli Prize in Astrophysics was awarded to Roger Angel, Jerry E. Nelson and Raymond N. Wilson (European Southern Observatory, Germany) for their contributions to the development of giant telescopes. The size of a telescope's primary mirror determines the light-gathering power and ability to detect and resolve the faintest and most distant objects in the universe. Nelson, Wilson and Angel pioneered the development of a new generation of large optical telescopes with innovations such as precise reflecting mirrors and more sophisticated shaping that has led to an extraordinary range of fundamental discoveries about the cosmos.

The 2010 Kavli Prize in Nanoscience was awarded to Donald M. Eigler and Nadrian C. Seeman for their development of unprecedented methods to control matter on the nanoscale. Eigler demonstrated it was possible to pick up and precisely place individual atoms at will, creating a whole field of quantum engineering. Seeman conceived the idea of using DNA as a building material for nanoscale engineering. Inventing DNA nanotechnology, he pioneered the use of DNA as a non-biological programmable material for a countless number of devices that self-assemble, walk, compute and catalyze. These discoveries promise breakthroughs in future applications in fields ranging from electronics to biology.

The 2010 Kavli Prize in Neuroscience was awarded to James E. Rothman, Richard H. Scheller and Thomas C. Sudhof for discovering the molecular basis of neurotransmitter release. Understanding how nerve cells communicate with one another has been a central problem in modern brain science. Over the past thirty years, Scheller, Sudhof and Rothman have used a creative multidisciplinary set of approaches to elucidate the key molecular events of neurotransmitter release. Moreover, their work has demonstrated that neurotransmitter release represents a special case of the fundamental cell biological process of membrane trafficking.

The Kavli Prize consists of a scroll, a gold medal and a cash award of one million dollars in each field, with the prizes awarded biennially. Kavli Prize recipients are chosen by committees comprised of distinguished international scientists recommended by the Chinese Academy of Sciences, the French Academy of Sciences, the Max Planck Society, the U.S. National Academy of Sciences and The Royal Society. After making their selection for Prize recipients, the recommendations are confirmed by the Norwegian Academy of Science and Letters. The formation of Prize Committees and the selection of prize recipients is independent of The Kavli Foundation - a nonprofit U.S.-based foundation dedicated to advancing science for the benefit of humanity, promoting public understanding of scientific research, and supporting scientists and their work.

The 2010 Kavli Prize Laureates were announced last year and received their awards in a ceremony held in Oslo, Norway. The call for nominations for the 2012 Kavli Prizes occurs this fall.


Rocky Kolb, U Of C Astronomy Prof: It's Time To Explore Asteroids
CBS Chicago, July 15, 2011
Prof. Rocky Kolb, KICP senior member.
Prof. Rocky Kolb, KICP senior member.
CBS Chicago

The head of the University of Chicago Astronomy and Astrophysics Department says it's time to look way beyond low-earth orbit for the nation's next space venture.

As WBBM Newsradio 780's John Cody reports, professor Rocky Kolb says the space shuttle helped keep the pioneering Hubble space telescope operating, but private industry can probably take over that job.


Related Links:
KICP Members: Edward W. Kolb

Dovetta McKee helps usher urban youths into college via Office of Special Programs-College Prep
The University of Chicago News Office, July 22, 2011
<i>Photo credit:</i> by Jason Smith
Photo credit: by Jason Smith
by Kadesha Thomas, The University of Chicago News Office

Dovetta McKee believes that every child has the potential to achieve academically, including disadvantaged youths, if given the opportunity and support. As the current director of the University's Office of Special Programs-College Prep, McKee is back where she got her career start in youth development.

From 1992 to 1999, McKee worked side by side with the late Larry Hawkins, who founded the office's landmark program Upward Bound. Hawkins, who was a high school star athlete, turned basketball coach, used sports to hook inner-city students into the academic program. McKee, who managed parent involvement activities, remembers how as many as 700 high school students would fill the programs and visit the University campus.

McKee took on the directorship in 2009 after Hawkins' death that year and now oversees his legacy, shepherding minority students from low-income South Side communities into college by providing a bridge to possibilities.

Between her UChicago stints, McKee was an associate professor at Aurora University, where she helped adults working in child development complete undergraduate degrees. She later became director of special initiatives at Prevention First, a program that partnered with Chicago Public Schools to tackle social issues that hinder academic success, such as neighborhood violence, teen pregnancy and substance abuse.

McKee brings her past experience to tackle some of those same issues and usher her students into college. "A lot of people do not believe that young African Americans can excel academically, and as a result they have very low standards for them," said McKee, who earned a law degree from John Marshall Law School. "People believe the hype; they believe what they see in the media, and the emphasis is always on the negative."

Despite relatively low graduation rates among urban high school students, youths who participate in the OSP-CP programs maintain a 100 percent high school graduation rate, up from 94 percent in 1997. Since 2007, between 85 and 100 percent have enrolled in four-year universities. Before then, the college enrollment rate was nearly 80 percent.

"When the bar is set high, and I have parents who are committed-even sometimes without committed parents-when I have young people who have been encouraged to believe in themselves, they do achieve," McKee said.

The OSP-CP operates throughout the school year, offering Saturday classes and campus tours at colleges and universities. Summer activities focus on math, science, foreign-language study and entrance exam preparation. The OSP-CP partners with the University's Kavli Institute for Cosmological Physics to expose students to scientific research and the University Theater to engage students in the arts. McKee's team also helps students develop soft skills like public speaking and punctuality.

The program's location on the University of Chicago campus reinforces its ability to give students an excellent pre-collegiate experience. "With any new adventure, you're always fearful because of the unknown," McKee explained. "It's imperative that young people from underserved communities see that people who work and learn on college campuses are just like everybody else. They need to know it's possible to cross the bridge and not fall in the river."


The Hunt for Dark Matter: A Conversation with KICP's Juan Collar
Kavli Foundation Newsletter, Vol. 4, Issue 3, 2011, September 2, 2011
Kavli Foundation Newsletter, Vol. 4, Issue 3, 2011

In June, it was announced that a dark-matter experiment had detected a seasonal signal variation similar to two other experiments that used different detectors. The new seasonal variation, recorded by the Coherent Germanium Neutrino Technology (CoGeNT) experiment, is exactly what theoreticians had predicted if dark matter turned out to be what physicists call Weakly Interacting Massive Particles (WIMPs).

Juan Collar of the Kavli Institute for Cosmological Physics, University of Chicago, led the team that detected the seasonal signal variation. In an extended interview, he discusses the significance of the finding and what will be needed to prove the existence of dark matter. "[It] gives you pause, the fact that the same kind of dark matter particle could be behind these three different observations from three very different detectors."

Related Links:
KICP Members: Juan I. Collar
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)

$10 million gift to enhance faculty support in Physical Sciences Division
The University of Chicago News Office, September 29, 2011
William Eckhardt, SM70
William Eckhardt, SM'70
by Steve Koppes, The University of Chicago News Office

A $10 million donation from futures trader and University of Chicago alumnus William Eckhardt, SM'70, will enable the Physical Sciences Division to respond rapidly and with flexibility to scholarly opportunities and challenges as they arise.

The donation will add to the division's discretionary funds, which are intended to address priorities as needed, including the recruitment and retention of prominent scholars.

"William Eckhardt has been a champion of scientific research, and an essential supporter of the University's efforts to bring innovative scholars to our campus and help them do their best work," said University President Robert J. Zimmer. "We are very grateful for this important gift."

Eckhardt said that one inspiration for his gift was his understanding that most scientific advances depend on an interplay between theoretical and applied science.

"Theoretical science is one of the glories of scholarship at the University of Chicago, and for me, one of the gratifying aspects of giving to the physical sciences is to be able to support that endeavor. They take theory seriously," he said.

The gift should benefit the division's faculty in many ways in the coming years, said Robert Fefferman, dean of Physical Sciences.

"William Eckhardt has made an historic commitment that will change the future of our division," said Fefferman. "What makes this gift so powerful is the flexibility that I or any dean in Physical Sciences will have in its use. To have a gift of this size directed to discretionary funds is quite rare, and it takes a very special appreciation and understanding of science to do that."

Eckhardt's appreciation for science extends to his hobbies, which include the study of quantum mechanics and the philosophy of time, Fefferman noted. "These are not hobbies that most people have. He has a firm technical grasp of science and mathematics that's rather astounding."

Eckhardt had previously donated $20 million to the division, which prompted the University to name the William Eckhardt Research Center in his honor.

A mixture of theoreticians and experimentalists will make their home in the Eckhardt Center, which will be under construction from late 2011 to late 2014. Moving into the Eckhardt Center will be the Department of Astronomy & Astrophysics, the Kavli Institute for Cosmological Physics, the theoretical physics group of the Enrico Fermi Institute, part of the James Franck Institute and the University's new Institute for Molecular Engineering.

"We want very much to attract not just excellent faculty members, but faculty members who will change the history of science, and we've done it. We've had historic-level scientists and mathematicians come here, and this latest gift will allow us to continue that effort," Fefferman said.

These scientists and mathematicians include a long list of Nobel laureates in physics and chemistry and of Fields medalists, recipients of the highest honor in mathematics. Two recent examples are Yoichiro Nambu and Ngo Bao Chau. Nambu, the Harry Pratt Judson Distinguished Professor Emeritus in Physics, shared the 2008 Nobel Prize in physics, while Ngo, the Francis and Rose Yuen Distinguished Service Professor in Mathematics, accepted an appointment at UChicago just months before receiving the Fields Medal last year.

Eckhardt's gift will help the Physical Sciences Division move quickly to recruit or retain such talent as the situations arise. Many scientists require precision equipment to conduct their research, and start-up funds to equip their laboratories have increased markedly in recent years. The cost of keeping top-performing, established scientists sought after by other institutions is rising as well.

"Here, with Mr. Eckhardt's gift, we have the ability to draw on resources to respond to the situation," Fefferman said.


2011 physics Nobel laureates collaborators on UChicago, Fermilab projects
The University of Chicago News Office, October 5, 2011
by Steve Koppes, The University of Chicago News Office

Two of the three recipients of the 2011 Nobel Prize in Physics are collaborators on cosmology projects led by the University of Chicago and Fermi National Accelerator Laboratory.

The physics Nobel was awarded on Tuesday, Oct. 4, "for the discovery of the accelerating expansion of the universe through observations of distant supernovae." One half of the prize went to Saul Permutter, a collaborator on the Dark Energy Survey.

The other half of the prize was shared by Adam Riess, a collaborator on the Sloan Digital Sky Survey's Supernova Survey, and Brian Schmidt, an astronomer at the Australian National University. Riess is a professor of astronomy and physics at Johns Hopkins University and an astronomer at the Space Telescope Science Institute.

"This was expected and well-deserved," said Joshua Frieman, a Fermilab scientist and professor in astronomy & astrophysics at UChicago.

Frieman founded and directs the Dark Energy Survey, a giant digital camera that is scheduled to probe the origin of cosmic acceleration from the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile.

The SDSS Supernova Survey, which operated from 2005 until 2008, discovered more than 500 type Ia supernovas for cosmological study. Perlmutter is an astrophysicist at the U.S. Department of Energy's Lawrence Berkeley National Laboratory and a professor of physics at the University of California at Berkeley.

Type Ia supernovas are exploding stars that shine with such predictable brightness that they are known as standard candles. This year's Nobel laureates and many other astronomers use them as astronomical measuring devices to help determine the expansion rate of the universe. By comparing a type Ia supernovae at the edge of the known universe to similar ones nearby, scientists can estimate whether the universe will expand forever or eventually collapse back into itself under the force of gravity.

Stephan Meyer, professor in astronomy & astrophysics, collaborated with another Nobel Prize-winning team on the Cosmic Background Explorer, which in 1992 confirmed that the universe was born in a hot big bang.


Related Links:
KICP Members: Joshua A. Frieman; Stephan S. Meyer

Nobel laureate John Mather to present Brinson Lecture on Nov. 1
The University of Chicago News Office, October 26, 2011
by Steve Koppes, The University of Chicago News Office

Cosmologist John C. Mather will deliver the 2011-2012 University of Chicago Brinson Lecture on "The History of The Universe in a Nutshell: From the Big Bang to Life and the End of Time."

The lecture will begin at 6 p.m. Tuesday, Nov. 1 in the MacLean Ballroom of the School of the Art Institute of Chicago, 112 S. Michigan Ave. Admission is free, and the event is open to the public. Mather's lecture is co-sponsored by the UChicago and SAIC with support from the Brinson Foundation.

Mather shared the 2006 Nobel Prize in Physics for his work on the Cosmic Background Explorer satellite. COBE's measurements of the cosmic microwave background radiation marked the first detection of hot and cold spots in the heat radiation from the big bang. Astrophysicists regard these measurements as the beginning of the era of precision cosmology. Mather currently is a senior astrophysicist at NASA's Goddard Space Flight Center in Maryland and the senior project scientist for the James Webb Telescope, the proposed successor to the Hubble Space Telescope.

During his lecture, Mather will explain Albert Einstein's biggest mistake, how Edwin Hubble discovered the expansion of the universe, how the COBE mission was built and how its data support the big bang theory.


2011-2012 Brinson Lecture: John Mather, "History of the Universe in a Nutshell: From the Big Bang to Life and the End of Time"
WBEZ 91.5, November 21, 2011
2011-2012 Brinson Lecture: John Mather, History of the Universe in a Nutshell: From the Big Bang to Life and the End of Time
WBEZ 91.5

Presented The University of Chicago via Chicago Amplified | Nov. 01, 2011

The history of the universe in a nutshell, from the Big Bang to now, and on to the future... John Mather tells the story of how we got here, how the universe began with a Big Bang, how it could have produced an Earth where sentient beings can live, and how those beings are discovering their history.

Mather was project scientist for NASA's Cosmic Background Explorer (COBE) satellite, which measured the spectrum (the color) of the heat radiation from the Big Bang, discovered hot and cold spots in that radiation, and hunted for the first objects that formed after the great explosion. He explains Einstein's biggest mistake, how Edwin Hubble discovered the expansion of the universe, how the COBE mission was built, and how the COBE data support the Big Bang theory. He also shows NASA's plans for the next great telescope in space, the James Webb Space Telescope. It will look even farther back in time than the Hubble Space Telescope, and will peer inside the dusty cocoons where stars and planets are being born today. It is capable of examining Earth-like planets around other stars using the transit technique, and future missions may find signs of life.

John C. Mather is an astrophysicist, cosmologist, and Nobel laureate. He was awarded the 2006 Nobel Prize in Physics for his work on COBE. Mather received his Nobel Prize for the precise determination that the spectrum of the cosmic microwave background radiation is that of a thermal source and the first detection and measurement of the anisotropy. These measurements marked the beginning of the era of precision cosmology. Mather is currently a senior astrophysicist at NASA's Goddard Space Flight Center in Maryland and the Senior Project Scientist for the James Webb Space Telescope, the successor to the Hubble Space Telescope.


Science pubs create lively intellectual exchange: UChicago speakers help bring informal research discussions to Chicago's suburbs.
The University of Chicago News Office, December 1, 2011
by Steve Koppes, The University of Chicago News Office

Allen Sanderson invited his audience in the banquet room at Grady's Grille in Homewood one evening last September to treat his presentation as a seminar in economics at the University of Chicago. He welcomed interruptions and even rudeness, but drew the line at throwing bottles across the room.

Sanderson, a senior lecturer in economics, was speaker of the month at the Homewood-Flossmoor Science Pub, a new forum for freewheeling exchange between interested members of the public and researchers of all stripes. The topic on the menu for the evening was "Sports, Statistics, and Economics."

Homewood resident Peter Doran, professor in earth and environmental sciences at the University of Illinois at Chicago, founded the H-F Science Pub after reading an article last January in USA Today.

"It was about a fad sweeping the nation called Science Pubs," he says. "I thought this was a great idea and started looking around for one of the local bars to hold it."

Such meet-ups create a valuable space for people who love science and research to come together as fans, rather than as students or professional colleagues. Organizers say the popular discussions have revealed a broad public appetite for informal events that are both intellectual and fun.

The venue alternates between Grady's Grille in Homewood and the Flossmoor Station Restaurant and Brewery, and routinely draws a capacity crowd of 40 or more. "Homewood-Flossmoor is a natural environment for this, with all the scientists who live in the area from the University of Chicago and the museum campus," Doran notes.

Science events grow in popularity

Doran gave the first talk, on "Human and Robotic science in the McMurdo Dry Valleys of East Antarctica." UChicago is contributing a continual stream of speakers, which began in May with Michael Coates, professor in organismal biology & anatomy at UChicago. Coates passed around a specially preserved dead fish during his humor-laced talk, playfully titled "The Incompleat Angler, or Fishing for Creatures from the Black Lagoon."

Following suit the next month, without the dead fish, was Rocky Kolb, the Arthur Holly Compton Distinguished Service Professor in Astronomy & Astrophysics. Kolb, author of Blind Watchers of the Sky, signed a small stack of his books for one woman after he described "The Dark Side of the Universe" to an appreciative audience.

Still other Science Pub speakers have come from UIC, the American Institute of Steel Construction and Indiana University Northwest.

UChicago alumna Stephanie Levi, PhD'09, began doing science outreach events called Night Lab for the public in 2008 at Schubas Tavern in Chicago's Lakeview neighborhood. A molecular geneticist and cellular biologist, Levi tweets at @scienceissexy and operates a Science is Sexy website. Levi will discuss "Sex and Attraction" Feb. 15 at the Divinity School's Wednesday Community Luncheon program, which offers speakers to the UChicago community in a spirit similar to the Science Pub and Cafe Scientifique. Her previous programs have been featured in the University of Chicago Magazine on coffee science and in a variety of other news outlets.

Public interest in science runs high in the Chicago area, if attendance at these and other events are any indication. Randy Landsberg, outreach director for the Department of Astronomy & Astrophysics and the Kavli Institute for Cosmological Physics, founded a Cafe Scientifique on the North Side in April 2006. The Cafe draws rave reviews at the Map Room, where it typically meets.

Last Nov. 1, more than 400 people attended Nobel laureate John Mather's UChicago Brinson Lecture. "We were over capacity," says Landsberg, a Brinson Lecture organizer. "Folks were almost literally hanging from the rafters."

On that same night, just a few blocks away at the Harold Washington Public Library, another capacity crowd of more than 400 heard Harvard physics professor Lisa Randall discuss her new book, Knocking on Heaven's Door in an Illinois Science Council event. Talks by visiting scientists in October and April also filled the library's auditorium.

The next H-F Science Pub takes place at 8 p.m. Nov. 29 at Grady's Grille, 18147 Harwood Ave. in Homewood. The speaker will be UChicago's Steven Simon, senior scientist in geophysical sciences, discussing "The Fall, Recovery, and Classification of the Park Forest Meteorite."

The Dec. 20 Science Pub at the Flossmoor Station will feature Kay MacLeod, associate professor in the Ben May Department for Cancer Research at UChicago. Her topic, beginning at 8 p.m., will be "Cancer's Sweet Tooth - How Tumors Acquire and Burn Energy Differently from Normal Tissue."


Related Links:
KICP Members: Edward W. Kolb; Randall H. Landsberg

New Twist in the Search for Dark Matter
Wired Science, December 2, 2011
The Bootes I dwarf galaxy. Sloan Digital Sky Survey
The Bootes I dwarf galaxy. Sloan Digital Sky Survey
by Adam Mann, Wired Science

Sometimes it seems like dark matter is intentionally trying to drive physicists mad.

New research using observations from dwarf galaxies has set a lower limit on the mass of dark matter particles. But the results contradict findings from several previous experiments, which observed dark-matter particles with masses below this threshold.

Dark matter is an invisible substance found throughout the universe that doesn't emit any light. Scientists know that if dark matter exists, then so does anti-dark matter, and putting the two together will cause them to annihilate each other and produce gamma radiation.

"We are looking for this byproduct of the annihilation," said physicist Savvas Koushiappas of Brown University in Providence, Rhode Island, who co-authored one of the papers, which will both be published Dec. 1 in Physical Review Letters.

Using NASA's Fermi Gamma-ray Space Telescope, Koushiappas' team and another group from Stockholm University in Sweden looked at data taken from seven dwarf galaxies - Bootes I, Draco, Fornax, Sculptor, Sextans, Ursa Minor, and Segue 1 - which are ideal targets because they are made up of as much as 99 percent dark matter.

After subtracting out the gamma-ray light from other sources, such as pulsars and supernovas, the teams calculated the portion of gamma radiation that should be due to dark matter annihilation. If the dark matter was lighter, there should be a lot more particles and therefore more radiation. But if the mass were larger, the radiation would not be as plentiful.

The researchers estimated from the amount of radiation that a dark matter particle's mass must be greater than 40 GeV, roughly 40 times the mass of a proton. This is strange because at least three prior experiments here on Earth have claimed to detect particles corresponding to dark matter with a mass between 7 and 12 GeV. Another observation, also using the Fermi telescope, had similarly found evidence for dark matter within this lighter mass range.

The explanation for this discrepancy may be relatively straightforward, however. The new research only imposes a constraint on one method that dark matter and anti-dark matter can annihilate, physicist Juan Collar of the University of Chicago, who leads the Coherent Germanium Neutrino Technology (CoGeNT) experiment that may have detected light dark matter, wrote in an email. This process is not the one favored by the researchers who previously used Fermi to see hints of less massive dark matter in the universe, so the existence of lighter dark matter isn't strictly ruled out, he added.

These underlying assumptions of the different experiments may be the reason for the disagreement, agreed Koushiappas. His team was looking for the most basic dark matter particles, but it is possible that dark matter is more complex than simple models predict.

"This is just a step in the puzzle," said Koushiappas.


Related Links:
KICP Members: Juan I. Collar
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)

Small reactors could figure into U.S. energy future
The University of Chicago News Office, December 13, 2011
Photo by Lloyd DeGrane
Photo by Lloyd DeGrane
by Steve Koppes, The University of Chicago News Office

A newly released study from the Energy Policy Institute at the University of Chicago (EPIC) concludes that small modular reactors may hold the key to the future of U.S. nuclear power generation.

"Clearly, a robust commercial SMR industry is highly advantageous to many sectors in the United States," concluded the study, led by Robert Rosner, institute director and the William Wrather Distinguished Service Professor in Astronomy & Astrophysics.

"It would be a huge stimulus for high-valued job growth, restore U.S. leadership in nuclear reactor technology and, most importantly, strengthen U.S. leadership in a post-Fukushima world, on matters of nuclear safety, nuclear security, nonproliferation, and nuclear waste management," the report said.

The SMR report was one of two that Rosner rolled out Thursday, Dec. 1, at the Center for Strategic and International Studies in Washington, D.C. Through his work as former chief scientist and former director of Argonne National Laboratory, Rosner became involved in a variety of national policy issues, including nuclear and renewable energy technology development.

The reports assessed the economic feasibility of classical, gigawatt-scale reactors and the possible new generation of modular reactors. The latter would have a generating capacity of 600 megawatts or less, would be factory-built as modular components, and then shipped to their desired location for assembly.

The U.S. Department of Energy funded the reports through Argonne, which is operated by UChicago Argonne LLC. The principal authors of the report were Rosner and Stephen Goldberg, special assistant to Argonne's director.

The reports followed up a 2004 UChicago study on the economic future of nuclear energy. The 2004 study concluded that the nuclear energy industry would need financial incentives from the federal government in order to build new plants that could compete with coal- and gas-fired plants.

The first report, "Analysis of GW-scale Overnight Costs," updates the overnight cost estimates of the 2004 report. Overnight costs are the estimated costs if you were to build a new large reactor 'overnight,' that is, using current input prices and excluding the cost of financing.

It would now cost $4,210 per kilowatt to build a new gigawatt-scale reactor, according to the new report. This cost is approximately $2,210 per kilowatt higher than the 2004 estimate because of commodity price changes and other factors.

Struggling restart
At the Center for Strategic and International Studies event on Dec. 1, CSIS president and CEO John Hamre said that economic issues have hindered the construction of new large-scale reactors in the United States. The key challenge facing the industry is the seven-to-nine-year gap between making a commitment to build a nuclear plant and revenue generation.

Few companies can afford to wait that long to see a return on the $10 billion investment that a large-scale nuclear plant would require. "This is a real problem," Hamre said, but the advent of the small modular reactor "offers the promise of factory construction efficiencies and a much shorter timeline."

Natural gas would be the chief competitor of nuclear power generated by small modular reactors, but predicting the future of the energy market a decade from now is a risky proposition, Rosner said. "We're talking about natural-gas prices not today but 10, 15 years from now when these kinds of reactors could actually hit the market."

The economic viability of small modular reactors will depend partly on how quickly manufacturers can learn to build them efficiently. "The faster you learn, the better off you are in the long term because you get to the point where you actually start making money faster," Rosner noted.

Small modular reactors could be especially appealing for markets that could not easily accommodate gigawatt-scale plants, such as those currently served by aging, 200- to 400-megawatt coal plants, which are likely to be phased out during the next decade, Rosner said. An unknown factor that will affect the future of these plants would be the terms of any new clean-air regulations that might be enacted in the next year.

An important safety aspect of small modular reactors is that they are designed to eliminate the need for human intervention during an emergency. In some of the designs, Rosner explained, "the entire heat load at full power can be carried passively by thermal convection. There's no need for pumps."

Getting the first modular reactors built will probably require the federal government to step in as the first customer. That is a policy issue, though, that awaits further consideration. "It's a case that has to be argued out and thought carefully about," Rosner said. "There's a long distance between what we're doing right now and actually implementing national policy."

The full reports can be downloaded at the Energy Policy Institute website.


Related Links:
KICP Members: Robert Rosner

South Pole centennial history includes UChicago telescopes
The University of Chicago News Office, December 14, 2011
The South Pole Telescope stands 75 feet tall, measures 33 feet across and weighs 280 tons. It was test-built in Kilgore, Texas, then taken apart and transported to the South Pole.  <i>Photo courtesy of Jose Francisco Salgado</i>
The South Pole Telescope stands 75 feet tall, measures 33 feet across and weighs 280 tons. It was test-built in Kilgore, Texas, then taken apart and transported to the South Pole.

Photo courtesy of Jose Francisco Salgado
by Steve Koppes, The University of Chicago News Office

Roald Amundsen reached the South Pole on Dec. 14, 1911. The following year, Arctic explorer Admiral Robert Peary wondered about the scientific merits of making a continuous year of astronomical observations from the South Pole. So Peary sent a letter to Edwin Frost, director of the University of Chicago's Yerkes Observatory, asking about the idea.

Frost rejected the idea, but his UChicago successors thought differently. In 1986 they established the first in a series of telescopes at the South Pole to take advantage of its high elevation (9,301 feet), its clear, dry atmosphere, and its uninterrupted view of the same patch of sky. UChicago scientists have since become a scientific fixture of the South Pole, which now enters its second century of human activity.

UChicago deployed its first telescopes as part of the Cosmic Background Radiation Anisotropy Experiment (COBRA). The largest COBRA telescope, called Python, recorded measurements of the cosmic microwave background - the big bang's afterglow - that were 10 to 100 times better than any other Earthbound site conducting such studies.

Then came Chicago's South Pole Infrared Explorer (SPIREX), the only telescope in the world that had a continuous view of the crash of Comet Shoemaker-Levy 9 with Jupiter in July 1995.

The Degree Angular Scale Interferometer (DASI), which began operating in 2000, soon recorded slight temperature fluctuations in the cosmic microwave background. DASI's precise measurements enabled cosmologists to verify the theory that ordinary matter, of which humans, stars and galaxies are made, accounts for less than 5 percent of the universe's total mass and energy.

DASI also made the first detection of the much fainter polarization in the cosmic microwave background, which made the cover of the Dec. 19, 2002 issue of Nature.

Succeeding DASI was the South Pole Telescope, which collected its first data in February 2007. SPT studies the mysterious phenomenon of dark energy, which makes the expansion of the universe accelerate.

The South Pole Telescope also will be featured as a Science Bulletin next summer in a high-definition, seven-minute documentary at the American Museum of Natural History in New York City.


Related Links:
KICP Members: John E. Carlstrom
Scientific projects: Degree Angular Scale Interferometer (DASI); South Pole Telescope (SPT)