Astronomy researcher challenges star cluster lifecycles

March 30, 2010 | Research, UToday
By Meghan Cunningham



A University of Toledo researcher is challenging the long-held belief that large clusters of stars exist for billions of years.

The existence of such large globular clusters in the Milky Way galaxy and many other nearby galaxies led to the belief that once formed, such massive clusters would be nearly impossible to destroy, but Dr. Rupali Chandar, UT assistant professor of astronomy, says that massive clusters that survive could actually be rare, with most rapidly falling apart.

Chandar received a National Science Foundation Career Award of nearly $729,000 over five years to test a new theory about the life cycle of star clusters. Most stars are believed to form in clusters, within giant clouds of cold and dense molecular gas. Little, though, is known about the clusters’ subsequent survival. The research project is called “The Life Cycle of Star Clusters: New Windows Into Star Formation and Galaxy Evolution.”

By studying star clusters in a number of galaxies, Chandar and her team are finding many huge young clusters that are only millions of years old, but few such clusters that are older. So either there was an extreme ramp-up in the formation of these clusters during a time representing the last 0.1 percent of the age of the universe, or the large clusters really don’t endure.

“The conventional wisdom has been that when these monsters form, they will be nearly impossible to destroy, hanging around for billions of years. It took us awhile to wrap our minds around the fact that 80 or 90 percent of them may actually be destroyed quite quickly, after only 10 million years,” Chandar said. “We’re starting to think those old large globular clusters that we see are just the skeletal remains of a much larger population, the lucky survivors.”

If Chandar’s team continues to find mostly young clusters as they expand their studies to more galaxies, about 30 in all, the next questions to delve into are why the lucky few have lasted billions of years and what causes most to quickly disperse.

Dr. Karen Bjorkman, Distinguished University Professor and chair of the Physics and Astronomy Department, said Chandar’s research has generated a lot of discussion in the astronomy community.

“Rupali has brought a lot of energy and enthusiasm to the department, and her research is creating a lot of waves and is challenging us to think differently about the formation of star clusters in galaxies,” Bjorkman said.

The Career grant also includes an outreach component, for which Chandar is developing a workshop to train middle school teachers to instruct students about the universe beyond our solar system, using lessons that students will find fun as well as educational. She also is organizing a day for middle school students to come to campus to learn about science and math with hands-on activities.

Chandar’s data comes from large telescopes on the ground, such as those located in Hawaii and Chile, and also from NASA’s Hubble Space Telescope as she works with other research teams to look into those findings.

Most recently, she was involved with the Hubble discovery of ancient galaxies coming together in the Hickson Compact Group 31. It is believed that the coming together of galaxies was common in the universe’s formative years, but this discovery shows a nearby example that is happening before researchers’ eyes at a time when the merging of multiple galaxies is much more rare.

“I’m lucky to have access to some of the best data in the world, taken both from space and ground-based telescopes, and to be working on research that has generated a lot of discussion among astronomers,” Chandar said.

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