Scientists find galaxy building block

By LIDIA WASOWICZ, UPI Senior Science Writer  |  Oct. 6, 2001 at 9:15 AM
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In an astounding discovery, astronomers peering through a "natural telescope" in space have gleaned what may be one of the long-sought building blocks of galaxies in the very beginnings of the universe.

The faint, small object some 13.4 billion light years from Earth may represent a galaxy in the making in the first half-billion years of the universe's existence, the international team reported. A light year is the distance light traveling at 186,000 miles per second covers in one year, or 6 trillion miles.

"With the discovery, we may finally be witnessing the circumstances in which (the) first generation of stars was born," said team member Konrad Kuijken of the Kapteyn Institute in The Netherlands.

These first galaxies hold clues to the enigmatic "Dark Ages," the billion or so years that started just after the Big Bang and ended when the first stars began to shine, scientists told United Press International.

The extraordinary discovery of the once-abundant precursors of modern-day star clusters was made possible through the exploitation of gravitational lensing, a phenomenon predicted by Albert Einstein's Theory of General Relativity, said lead study author Richard Ellis, professor of astronomy at the California Institute of Technology in Pasadena, Calif.

The space sleuths spied on small areas of sky through a massive intervening cluster of thousands of galaxies, called Abell 2218, 2 billion light years away. The cluster acts as a powerful cosmic lens, magnifying distant objects and providing a window into the assembling of galaxies far, far away and long, long ago, investigators said.

Gravitational lenses, acting as "natural telescopes," give researchers a unique tool with which to learn more about the detailed physics of the first galaxies, scientists said.

Because, according to Einstein's theory, mass curves space, a massive object in the foreground bends the light rays radiating from one behind it. Much like glass lenses in binoculars that direct more photons, or light particles, toward the eyes, the galaxy cluster bends additional photons from the object behind it toward Earth, making it appear much brighter -- 30 times more so in this case.

Without this superficial boost in brightness, the object -- which is only 500 light years across as compared to 100,000 for the Milky Way -- would be detectable through neither the Hubble Space Telescope nor the 10-meter (33-foot) Keck Telescopes atop Mauna Kea in Hawaii. The scientists said they made their discovery by pushing both instruments to the limit.

"Without gravitational lensing, this wouldn't have been possible, period," team member Michael Santos of Caltech told UPI. "Without lensing it would have taken a 50-meter (166-foot) telescope to do what we did with the 10-meter Keck -- the Kecks are the largest optical telescopes in the world, and probably will be for several years to come."

"We've found a clever way to use the telescope in a more powerful way than normal and which has great practical applications in letting us get a glimpse of stars when they were first forming," Ellis told UPI. "The technique can be used over the next few years to see when the first stars formed and started shining, something you can't learn by looking up and examining big shining objects."

Using the Keck, the astrophysicists found a faint signal corresponding to a pair of feeble images in a space telescope picture, which spectroscopic studies confirmed arose from an extremely distant single source in the process of formation.

"The system contains about a million or so stars at a distance of 13.4 billion light years, assuming that the universe is 14 billion years old," Ellis said. "While more distant galaxies and quasars have been detected with the Keck Telescopes, by virtue of the magnification afforded by the foreground cosmic lens, we are witnessing a source much smaller than a normal galaxy forming its first generation of stars."

"Our work is a little like studying early American history. But instead of focusing on prominent individuals like George Washington, we want to know how everyday men and women lived," Santos said. "To really understand what was going on in the early universe, we need to learn about the typical, commonplace building blocks, which hold important clues to the later assembly of normal galaxies. Our study represents a beginning to that understanding."

The finding, detailed in the Oct. 20 issue of Astrophysical Journal Letters, caused "big excitement," Santos recalled.

"It took two observing runs with the Keck Telescopes before we had gathered enough light from this feeble object to determine its distance and thus confirm the discovery," said Jean-Paul Kneib, a gravitational lensing expert at the Observatoire Midi-Pyrénées near Toulouse, France. "When we realized what we had found, we literally jumped up and down."

What they found was something very small and very young.

"A 2-million-year-old, 1-million-solar mass, galaxy-like object consisting of young hot stars is the best fit to the observations," Kuijken said. "We believe it is one of the galaxy building blocks that join together and make up larger galaxies later in the history of the universe."

"We call the discovery 'first light' not because these are the first stars in the universe, but because they are probably the first stars in this system," Santos said. "Thus begins the process of forming stars from gas that eventually leads to bright galaxies with lots of stars, like our Milky Way, and also stars are the chemical processing plants which produce elements like carbon, which are required to ultimately produce life on Earth."

The team has applied for additional time at the Keck and on the Hubble in hopes of finding more similar objects and answering questions regarding their numbers and chemistry and the birth rates and frequency of stars formed in their systems, which affect numerous processes in the universe, scientists said.

"The number and properties of these objects will also help guide future projects that aim to study them without the benefit of lensing -- many decades from now when we have 10-meter space telescopes and 50-meter ground telescopes," Santos said.

"I think wanting to understand the beginnings of our galaxy, and the beginnings of the chemistry which leads to life, is natural. So much of my personality comes from my childhood and young adulthood; in many people you can see where they came from in who they are today. Our universe is the same way: when we look around at where we've gotten to, and want to understand why it is the way that it is, we need to ask: where did it come from?"

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