First Stars in Universe Detected?

Brian Handwerk
for National Geographic News
November 2, 2005

NASA researchers say they have detected what may be the faint infrared glow of the first stars in the universe.

Known as population III stars, the distant bodies are thought to have formed just 200 million years after the big bang, the event that in theory created the universe some 14 billion years ago.

The original stars formed from gas and dust in the void of space and are thought to have been many times more massive than today's stars. The ancient stars remain invisible to telescopes and have never been detected before.

"They have basically been theoretical objects," said Alexander Kashlinsky, an astronomer at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Using NASA's orbiting Spitzer Space Telescope, Kashlinksy and his colleagues identified the stars indirectly by measuring the enduring energy that they once radiated into the void of space.

Cosmic Radiation

As the universe expands, starlight is stretched into longer, redder wavelengths. Most emissions from the first stars in the universe would appear today as infrared light.

The universe is filled with background radiation known as the cosmic infrared background (CIB). This includes radiation from all stars—young and old, near and far.

"If these [earliest stars] were very massive and formed in the standard cosmological mode, they should have left a signature in the fluctuations of the CIB. That's the signal we sought to measure with these observations," Kashlinsky said.

To detect the original stars, the team had to isolate their energy from that of countless other bodies, a task akin to picking out a group of voices amid cheering fans at a crowded sports stadium.

"Imagine a field filled with electric bulbs of varying intensity, from one watt to several hundred watts," Kashlinsky explained. "You look at this field, and you want to actually see the faintest bulbs."

"So you start removing bright bulbs that you can individually identify. Once you've done that, you can see an image of what the field is like and what it is filled with. From that, you can deduce a collective signal."

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