When something reaches a distance of tens of billions of light-years away, there's a slim chance we're going to spot it. For the Hubble Space Telescope to catch these faint flickers of light, they have to be something with a pretty powerful glow, like supernovae, gamma ray bursts or bright galaxies. But as Elizabeth Howell at Space.com reports, using a special technique, the Hubble caught a glimpse of a regular old star that lies 9 billion light years away, the most distant single star yet detected.
The new star is officially named MACS J1149+2223 Lensed Star 1, but the researchers have mercifully given it the nickname Icarus. They spotted the star while looking at a distant supernova called SN Refsdal, which was discovered in 2014. To get a better look at the supernova, the astronomers used a technique called gravitational lensing. This takes place when the gravity of supermassive objects bends and amplifies the light from behind them. Astronomers can exploit this property, lining their faint object up with a massive one to get a better look.
When astronomers discovered Icarus, they were using a galaxy cluster five billion light years away in the constellation Leo to get a better look at Refsdal. As co-author Mathilde Jauzac of Durham University tells Nicola Davis at The Guardian, the team had been monitoring Refsdal on a regular basis when they spotted a region that seemed to be growing brighter over time, calling this the "Icarus region."
This change in intensity was thanks to the passing of a star within the galaxy cluster about the size of our own sun. While the galaxy cluster was acting as a gravitational lens for Refsdel, this one star passed directly in front of Icarus, intensifying the magnifying effect. Researchers estimate Icarus was magnified more than 2,000 times. They described the find in a study published in the journal Nature Astronomy.
“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," University of California Berkeley astronomer and co-author Alex Filippenko says in a press release. “These lenses are amazing cosmic telescopes.”
By examining the light coming from Icarus, the researchers determined that it’s a blue supergiant, which is hotter, larger and could even be hundreds of thousands of times brighter than our own sun. Still, it would have been impossible to see without the effects of the gravitational lens.
Icarus, however, no longer exists. As Ben Guarino at The Washington Post reports, blue giants can't survive for nine billion years; the star likely collapsed into a black hole or neutron star many years ago.
But it’s possible we could still get an even closer look. According to the press release, movement of stars within the galaxy cluster could create an even more powerful lens in the future, amplifying the star as much as 10,000 times. “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," Filippenko says. “For this type of research, nature has provided us with a larger telescope than we can possibly build!”
This is not the first time gravitational lensing has given us a glimpse into the past that wouldn't be possible with a backyard telescope. In January, astronomers announced that they had imaged a galaxy 13.3 billion light-years away using gravitational lensing, the farthest galaxy ever captured. In February, researchers also announced that lensing helped them find possible signs of planets outside our own galaxy.