For the first time, astronomers have made direct measurements of the size and brightness of regions of star-birth in a very distant galaxy, thanks to a chance discovery with the Atacama Pathfinder Experiment (APEX) telescope. The galaxy, later named SMM J2135-0102, is so distant, that its light has taken 10 billion years to reach us. A cosmic “gravitational lens” is magnifying the galaxy, giving us a close-up view that would otherwise be impossible. This lucky break reveals a hectic and vigorous star-forming life for galaxies in the early Universe, with stellar nurseries forming one hundred times faster than in more recent galaxies.
The star factories in SMM J2135-0102 are similar in size to those in the Milky Way, but one hundred times more luminous, suggesting that star formation in the early life of these galaxies is a much more vigorous process than typically found in galaxies that lie nearer to us in time and space.
Thanks to a fortunate alignment between the cluster and the distant galaxy, the light signal from SMM J2135-0102 is magnified by a factor of 32. The magnification means that the star-forming clouds can be picked out in the galaxy, down to a scale of only a few hundred light-years. To see this level of detail without the help of the gravitational lens would need future telescopes such as ALMA (the Atacama Large Millimeter/submillimeter Array), which is currently under construction on the same plateau as APEX. This lucky discovery has therefore given astronomers a unique preview of the science that will be possible in a few years time.