Newborn stars discovered in dramatic galaxy tail (9/22/2007)

This composite image of Abell 3627 was gathered from the SOAR telescope and the Chandra X-ray Observatory.

A team of astronomers, including several from Michigan State University, has discovered a number of stars forming in a section of our universe that is not normally conducive to the birth of stars.

Typically, stars form within galaxies that contain large clouds of molecular hydrogen gas, the raw material for star formation. The vast spaces in between galaxies have been considered unlikely places for star formation because they are generally devoid of the molecular hydrogen gas needed to make stars.

However, new observations from MSU astronomers Ming Sun, Megan Donahue and Mark Voit, using MSU's SOuthern Astrophysical Research, or SOAR, telescope and NASA's Chandra X-ray Observatory, are challenging this long-held viewpoint.

The SOAR telescope - a 4.1-meter instrument located in the Andes Mountains in Chile - is a joint project between MSU, the University of North Carolina at Chapel Hill, the country of Brazil and the National Optical Astronomy Observatories.

Their pictures of a galaxy named ESO 137-001, about 215 million light years from Earth, show that it is falling through a cluster of galaxies known as Abell 3627.

Sun, an MSU postdoctoral researcher, noticed in an image obtained with the Chandra X-ray Observatory that this galaxy has an unusually long tail of hot gas trailing behind it, extending more than 100,000 light years from the galaxy. The tail looks similar to a comet's tail and consists of matter stripped out of the galaxy as it passes through the super-hot gas between the cluster's galaxies.

"This is one of the longest tails like this we have ever seen," Sun said. "And it turns out that this is a giant wake of creation, not of destruction."

The high-temperature gas detected with the Chandra X-ray telescope is too hot to form stars, but follow-up observations of the tail with MSU's SOAR telescope have revealed clouds of star-forming gas within the X-ray tail.

MSU analysis of the images collected by the SOAR telescope found that those young stars formed within the last 10 million years, a relatively short time period compared with the 10 billion-year lifespan of a star like our sun.

"This isn't the first time that stars have been seen to form between galaxies," said Donahue, an associate professor of physics and astronomy. "But the amount of stars forming here is unprecedented."

Further observations of this galaxy will be particularly interesting because it may represent an important but short-lived stage in galaxy development.

Astronomers have long known that most of the galaxies belonging to large clusters of galaxies like Abell 3627 are no longer forming stars. The suspicion has been that star formation has ceased in those galaxies because their star-forming gas has been stripped away as they move through the cluster.

That is exactly what seems to be happening here but with an unexpected twist - the stripped gas is continuing to form stars even out in intergalactic space, adding new stars to the spaces in between galaxies.

"By our galactic standards, these are extremely lonely stars," said Mark Voit, MSU professor of physics and astronomy. "If life was to form out there on a planet, they would have very dark skies."

This process is apparently rare in the present-day universe but may have been more common billions of years ago when galaxies were younger and richer in star-forming gas.

These results will appear in the Dec. 10th issue of The Astrophysical Journal.

The SOAR telescope is a joint project of MSU, Conselho Nacional de Pesquisas Científicas e Tecnológicas (CNPq-Brazil), the University of North Carolina at Chapel Hill, and the National Optical Astronomy Observatory. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

NASA's Chandra X-ray Observatory, which was launched and deployed by Space Shuttle Columbia on July 23, 1999, is the most sophisticated X-ray observatory built to date. Chandra is designed to observe X-rays from high-energy regions of the universe, such as the remnants of exploded stars.

Note: This story has been adapted from a news release issued by Michigan State University

Post Comments: