Scientists discover possible early galaxy during its first years

Celestial phenomenon helps telescope see objects deep in space

October 05, 2001|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Using a celestial oddity to boost its telescope's power, a team of American and European astronomers has detected what may be one of the universe's earliest galaxies in its infancy.

The feeble little galaxy - a cluster of only a few million young stars - is thought to be the first example ever observed of what some theorists suggest was once a population of fragmentary "building-block" galaxies, which later merged to form the vast galaxies that dominate the universe.

"We would expect to find many more of them if the theory is correct," said Richard Ellis, professor of astronomy at the California Institute of Technology, whose team is seeking more. The work was published in the latest Astrophysical Journal Letters. To see that far back in time, astronomers have to look deep into the most distant reaches of space. That's because the light from those regions has been en route for the longest time, revealing objects as they appeared when the light began its journey.

Small, faint objects can't be seen at such distances, not even with the Hubble Space Telescope. So, Ellis and his team sought to harness a natural phenomenon, called "gravitational lensing," to boost the power of their telescope.

As Albert Einstein predicted, scientists have found that light from remote objects can be bent by the gravity of any large objects that lie along its path.

With the right geometry, this light-bending works like a magnifying glass, revealing what would otherwise be invisible.

One such lens was created by a cluster of galaxies called Abell 2218, about 2 billion light years from Earth. Found by the Hubble Space Telescope, it has a total mass equivalent to 10,000 galaxies the size of the Milky Way - enough light-bending power to make objects behind the cluster look 30 times bigger and brighter.

In April and May, using the Keck Telescope in Hawaii, Ellis and his team scanned all the starlight streaming past Abell 2218. They quickly found light from a faint cluster of stars far behind Abell 2218, and 13.4 billion light years from Earth. The light left those stars less than a billion years after the Big Bang. Analyzing the feeble glimmer, the astronomers determined that the cluster was one-twentieth the size of the Milky Way, with only a few million sun-sized stars. None had been shining for more than a million years. "We are seeing it at a moment in its life when it is forming stars for the first time," Ellis said.

James Peebles, a theoretical cosmologist at Princeton University not involved in Ellis' discovery, said sky surveys have found evidence of huge, mature galaxies at the same moment in time, supporting those who say the big galaxies appeared fully formed, soon after the Big Bang.

Ellis agreed but said such big, early galaxies were extremely rare, whereas his data suggest that the early universe teemed with small ones that probably fed the growth of the giants that now dominate.

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