Fewer stars form as galaxies run out of gas
Star formation peaked early in the universe`s history, about 8 to 10 billion years ago, then began to decline.
Washington: The Universe is forming fewer stars than it did over 8 billion years ago and scientists believe that it is because galaxies are, quite literally, running out of gas.
Dr Robert Braun (CSIRO Astronomy and Space Science) and his colleagues used CSIRO’s Mopra radio telescope near Coonabarabran, NSW, to study far-off galaxies and compare them with nearby ones.
Braun, said that star formation peaked early in the universe`s history, about 8 to 10 billion years ago, then began to decline. At first the drop-off in star birth was slow. ``Now it`s really plummeting,`` Dr Braun said.
After stars form, they shed gas during various stages of their lives, or in dramatic events such as explosions (supernovae).
This returns some gas to space to contribute to further star formation.
“But most of the original gas—about 70 percent—remains locked up, having been turned into things such as white dwarfs, neutron stars and planets,” Dr Braun said.
Dr. Braun blames the hypothetical dark energy that drives galaxies apart for the missing gas.
This accelerating expansion will have made it increasingly difficult for galaxies to capture the additional gas they need to fuel future generations of star formation, Dr Braun speculates.
The study will be published in the monthly notices of the Royal Astronomical Society.