The NASA Hubble Space Telescope has captured an image of a star roughly nine billion light years away from Earth, using a phenomenon called gravitational lensing. The blue supergiant, named MACS J1149 Lensed Star 1 (LS1) and also known as Icarus, is the most distant star ever detected by astronomers. It was first spotted in images taken by NASA in late April of 2016 as well as in April of the following year.
Galaxies that are billions of light years away can be routinely studied by astronomers since these galaxies glow with the brightness of billions of stars that lie within them. A supernova, which is brighter than the galaxy it lies in, can also be spotted by astronomers. However, it is very difficult to make out individual stars in galaxies that are more than 100 million light years away.
“You can see individual galaxies out there, but this star is at least 100 times farther away than the next individual star we can study, except for supernova explosions,” says Patrick Kelly, one of the authors of the paper on the discovery published in the international journal Nature Astronomy.
Gravitational lensing, the bending of light by the gravity of supermassive objects, enables astronomers to get a look at distant universe by making dim, far away objects visible. This phenomenon typically magnifies galaxies by up to 50 times, but in this instance, the star was magnified more than 2,000 times.
Astronomers were initially looking at a distant supernova called SN Refsdal which was discovered in 2014. They were using a galaxy cluster in the the constellation Leo as a gravitational lens to get a closer look at Refsdal. However, a rare cosmic alignment took place as a star about the size of our Sun, within the galaxy cluster, aligned precisely with Icarus. This increased the magnifying effect of its brightness to more than 2,000 times and made Icarus easily visible.
“For the first time ever, we’re seeing an individual normal star – not a supernova, not a gamma ray burst, but a single stable star – at a distance of nine billion light years,” says Alex Filippenko, a professor of astronomy at UC Berkeley and another co-author of the paper in a press release. “These lenses are amazing cosmic telescopes.”
“There are alignments like this all over the place as background stars or stars in lensing galaxies move around, offering the possibility of studying very distant stars dating from the early universe, just as we have been using gravitational lensing to study distant galaxies,” adds Filippenko. “For this type of research, nature has provided us with a larger telescope than we can possibly build.”
Astronomers say that this technique might help them understand how stars evolve, especially the most luminous ones. They believe that Icarus might be magnified many more times over the next decade, by even as much as 10,000 times, as more stars move around.