Press Release - 4 June 2001

198th Meeting of the American Astronomical Society
Pasadena, CA, USA

 

ASTRONOMERS FIND WIND BUBBLE AROUND YOUNG SUPER STAR CLUSTER


An international team of astronomers announced the detection of a wind bubble associated with a super star cluster in a nearby galaxy. The bubble is caused by the combined action of winds from a young cluster of massive stars.

"We have detected supersonic motions in the nebula surrounding this super star cluster", says Jean L. Turner, UCLA professor and principal investigator. "We know of smaller wind bubbles around hot young stars in our own Milky Way, but this wind is far more powerful, with the potential to seriously disrupt its parent galaxy."

The findings of the team, which include Lucian P. Crosthwaite and David S. Meier, UCLA graduate students, and Sara C. Beck from Tel-Aviv University's Wise Observatory, were reported at today's meeting of the American Astronomical Society in Pasadena. The discovery, supported by funding from the National Science Foundation, was made with infrared spectra taken at the W. M. Keck Observatory in Hawaii, operated jointly by the University of California and the California Institute of Technology, with support from NASA.

"We're detecting wind speeds of about 3000 miles per hour in the hydrogen gas", says Crosthwaite. "These are not unusual speeds for stellar winds. But stellar winds normally involve only a little mass. This wind is exceptional because it is pushing a million earth masses of gas, so it's far more powerful than what we have seen before".

The wind arises in a gas cloud that hides what may be the youngest known super star cluster, located in a galaxy about 12 million light years away in the direction of the constellation Centaurus. The star cluster estimated to contain a million young stars is so young, in astronomical terms, that it is still hidden from optical view by a hot and glowing cloud of gas and dust. These luminous young stars drive winds by the sheer force of their radiation pressure, and their combined results in the detected wind bubble. Although only a few light years across, the distance from the Sun to the nearest star, the cluster and its windy cocoon emit the power of a billion suns, and are responsible for nearly one quarter of the energy output of the entire galaxy.

"We estimate from its current rate of expansion that this phase of the life of this super star cluster can be at most 15,000 years, unless gravity is slowing the expansion, which is likely," says Meier. "Even so, this cloud is evolving rapidly and it may prevent future star formation in the immediate vicinity."

Super star clusters were formed in the Milky Way billions of years ago, and were more common in the early universe. The effects of these luminous young clusters on galaxies are unknown. According to Beck, "We've known for some time that galaxies undergoing bursts of star formation make super star clusters and we've suspected that the winds of these clusters could strongly affect the evolution of the parent galaxies. But this is a very short-lived phase in the life of the cluster so it's hard to catch one in the act. We are lucky that NGC 5253 is at the right place and the right time for us to detect and study this extraordinary wind-blown bubble."

More information about the globular cluster research is available here.


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