One thing that all stars have in common is that they are bright. And the bigger they are, the brighter they are.
At least, that's how things work today. But it could have been quite different in the very early universe. In fact, a recent study says that the earliest stars could have been gigantic but invisible.
The study was led by Paolo Gondolo of the University of Utah. It found that the first stars in the universe might have been kept dark by dark matter -- matter that produces no energy, but that exerts a gravitational pull on the normal matter around it.
Stars are born when giant clouds of gas collapse. When the gas gets packed tightly enough, it ignites the fires of nuclear fusion, and the star shines brightly.
But conditions in the first few hundred million years after the Big Bang were quite different. The universe was much smaller, so everything was packed tighter. As stars began to form, they contained high concentrations of dark matter.
The study says that particles of dark matter may have interacted with each other, producing other particles that heated the collapsing clouds. The heat kept the clouds from shrinking enough to ignite nuclear fusion.
So instead of the glowing orbs we see today, this early process formed giant dark stars. They were far larger than the Sun, but produced no visible light. But they would have produced other forms of energy, giving astronomers a chance to hunt for evidence of dark stars in the early universe.
Script by Damond Benningfield, Copyright 2008
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