Scientists believe that the birth of new stars in the universe has greatly declined
Research indicates stars began forming around 13.4 billion years ago. (Mehau Kulyk / Science Photo Library / Corbis)
Is the universe getting darker? One group of scientists believes so. Their research suggests the birthrate of stars has declined over the past few billion years.
In the largest study of its kind, astronomers used special telescopes to survey star-forming galaxies. They looked at the light, gas, and dust from stars to see how fast they form and how their conditions change over time. They found that star production has been declining over the past 9 billion years.
A BRIGHT HISTORY
Stars are bright balls of hot gas held together by gravity. They form when clouds of dust and gas in the universe become unstable and collapse under their own gravity. The center of this material becomes dense and hot, causing a nuclear reaction. When that happens, the cloud begins to shine as a star.
Research suggests that star formation began around 13.4 billion years ago. But it was the period between 11 billion and 9 billion years ago that star production really boomed, generating roughly half the stars in the universe. Now, star formation is at only one-thirtieth of that rate.
You might say that the universe has been losing lights for a long time: Cosmic output is now only 3 percent of what it used to be at the peak of star production, says David Sobral, a researcher from the Institute for Astronomy, University of Edinburgh, UK.
If star production continues declining as it has, astronomers estimate that only 5 percent more stars will form over the remaining history of the universe.
That doesn’t mean the sky will turn dark anytime soon. The life of a single star can last billions of years. But it does mean that fewer stars are forming now than when the universe was younger.
“While these measurements provide a sharp picture of the decline of star formation in the universe,” says Philip Best of the Institute for Astronomy, “they also provide ideal samples to unveil the even more fundamental mystery which we are continuing to work to solve: Why?”