Star-filled evening


Covering everything from galaxy "mergers and acquisitions" to gamma rays shooting from black holes, ten Chicago astronomers and astrophysicists led a so-called "cosmic tour" of the universe Wednesday night at the Art Institute. Seated beneath spotlights on a dark and cavernous stage, University cosmologists Rocky Kolb and Michael Turner emceed the evening, peppering their colleagues, who appeared in panels of two or three, with questions about their research. Nobel laureate and physics professor emeritus James Cronin, SM'53, PhD'55, explained a recent "fundamental discovery" from the Pierre Auger Observatory in Argentina: the high-energy cosmic rays constantly showering Earth come from the violent cores of nearby galaxies.

Chicago professor and Fermilab researcher Joshua Frieman described the Sloan Digital Sky Survey. Begun in 1998, it aims to map a quarter of the heavens in detail and illuminate how cosmic structures are formed. "We're doing archaeology on a grand scale," Frieman said. "We're using galaxies like pottery shards." Associate professor Andrey Kravtsov explained that dark matter, a still-mysterious entity that makes up most of the universe's mass, holds galaxies together. In about three billion years, he added, the Milky Way Galaxy will collide with its nearest large neighbor, the Andromeda Galaxy. "But don't worry, nothing will happen to the sun or anything," he said, detecting a nervous rustle among the audience. "If you want to stick around," he added, "the sky will be spectacular."

Punctuated by questions from the crowd, which filled the main floor and spilled into the auditorium's balcony, the program stretched past two hours. The scientists—each of whom brought a short video to illustrate their work—described their research, such as using a ten-meter telescope to scan the Antarctic sky for dark energy, a hypothetical force believed to accelerate the universe's expansion; or searching for dark matter, which emits too little light to be seen but nevertheless exerts gravitational power, in South Dakota mines and Cook County municipal tunnels, where surface-level cosmic rays won't disrupt the sensitive detectors. "How will we know if you find dark matter?" Kolb asked assistant professor Juan Collar. Joked Collar, "I will call you right away."

Capping the evening with one final question, an audience member asked, "What good will all this information do?" Kolb offered a philosophical response: "For the last 6,000 years," he said, "people have looked to the sky and wondered what's out there. It's our human curiosity, and once these cosmic questions are answered, there will be other, deeper cosmic questions."


Photo: Chicago astrophysicist Andrey Kravtsov (second from left) displays a video simulation of dark matter's cosmic rotation while colleagues (left to right) Michael Turner, Michael Gladders, Joshua Frieman, and Rocky Kolb look on.

December 7, 2007