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Satellite finds faint glow of time’s beginning

SHARE Satellite finds faint glow of time’s beginning

After a remarkable technical and scientific effort that spanned 23 years, a team of astronomers Friday reported that they had found a faint, warm glow that comes from the accumulated radiation of virtually every star that has existed since the universe was born.

This background radiation of infrared light seen in every part of the sky was picked up by a satellite called COBE, or Cosmic Background Explorer, that was launched in 1989. It took years of painstaking analysis and computation by a large team of astronomers to eliminate all the extraneous sources of infrared light from the data and end up with just the "fossil radiation" of past starlight."For the first time, we've detected . . . starlight that was emitted from all the stars that ever existed," said Eli Dwek, an astronomer at NASA's Goddard Space Flight Center and member of the team responsible for COBE's Diffuse Infrared Background Experiment. The results were presented Friday at a meeting of the American Astronomical Society.

The infrared glow, the astronomers believe, comes primarily from clouds of dust warmed by the stars. This radiation, which turned out to be about twice as bright as predicted, shows that "in the early universe, a lot of star formation was taking place in dusty regions," said David Spergel, a Princeton University theoretical astrophysicist who was not involved in the COBE work.

Many astronomers had thought that in the first few billion years of the universe, there was relatively little dust, Spergel said, but the new data suggest that was not the case. Also, by placing limits on how much light has been emitted by stars since the universe began, the findings will knock down or require the modification of some theories of how stars and galaxies originated, Spergel said.

"People have been trying to find this for a long time," Spergel said. "It's quite an accomplishment."

When stars are surrounded by dust, starlight warms the dust, which then emits a glow of infrared light, or heat radiation - the same light detected by infrared cameras used to detect heat escaping from a poorly insulated house, for example. It is this glowing dust that the experiment was primarily designed to detect - although there could also be other sources contributing some of the light, such as stars that formed so early on that their light has been "redshifted" by their motion away from us so that it now appears as infrared.

This infrared glow, said team leader Michael Hauser, is "something like a cosmic safety-deposit box where most of the radiation emitted since the universe formed is still collected."

But it took years of painstaking analysis to subtract out from the data, which covered the entire sky, all the infrared radiation from other, more nearby sources of infrared radiation. Every object warmer that absolute zero emits some infrared, including the satellite itself, which was cooled to minus 454 degrees Fahrenheit to minimize its glow. The astronomers also had to eliminate from the data the radiation that came from interplanetary dust that surrounds the Earth and the rest of the inner solar system, dust in the regions between stars in our own galaxy, and stars themselves.