Stars make an early entrance
Jul 23, 2003
Astronomers have found evidence for star formation in the earliest known object in the universe. Fabian Walter of the National Radio Astronomy Observatory in the US and colleagues in France, Germany and the US detected the tell-tale signature of carbon monoxide in the infrared emissions of quasar J1148+5251. The discovery suggests that star formation was already underway just 800 million years after the big bang (F Walter et al 2003 Nature 424 406).
Stars are born when dense clouds of molecular hydrogen gas implode under the influence of their own gravity. As more and more gas is pulled in, pressure builds up and eventually triggers nucleosynthesis, the process that forges all heavier elements. At the ends of their lives, many stars explode in supernovae that eject heavy elements into space.
With a redshift of 6.42, quasar J1148+5251 is the most distant – and therefore the oldest – object ever observed. Walter and co-workers used the Very Large Array telescope in New Mexico to observe the galaxy around quasar J1148+5251. It is difficult to detect molecular hydrogen directly, but previous studies have strongly linked carbon monoxide with regions of star formation. This is because the atomic hydrogen formed after the big bang must cool in order to form molecular hydrogen, and the presence of carbon monoxide allows this heat to radiate away.
According to the team’s calculations, stars in the ancient galaxy may have formed at a rate of 3000 solar masses a year. The researchers also spotted the spectral signatures of heavy metals in the infrared emissions, which suggests that at least one cycle of stellar evolution must have taken place by this early stage.
Astronomers hope that the next generation of ultra-high-resolution radio telescopes, such as the Atacama Large Millimeter Array, will allow them to peer even further back in time to establish exactly when star formation began.
About the author
Katie Pennicott is a science writer living in Bristol, UK