Astronomers Just Found the Most Distant Star Ever Observed: A Giant Blue 'Sun' 9 Billion Light-Years Away
Astronomers can spot supernovas from a galaxy away (even quick ones), but observing individual stars is much harder. In the cosmic background noise, picking out the light of even a giant star would be near-impossible without a phenomenon called gravitational lensing. Luckily for astronomers, a stroke of interstellar luck has allowed them to spot the most distant "normal star" ever observed, a blue supergiant star named MACS J1149 Lensed Star 1 (LS1), also known by the name Icarus.
Icarus is about 9 billion light-years away, which is far away even in cosmic terms—the distance between the Milky Way and Andromeda galaxies is about 2.5 million light years, while the observable universe is about 92 billion light-years in diameter, meaning that the distance between us and this newly discovered blue giant is about 10 percent of the total width of all of creation.
Usually, stars beyond a distance of 100 million light years are invisible to telescopes. According to Patrick Kelly, from the University of Minnesota, Twin Cities: "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."
The only reason astronomers were able to spot Icarus was because a Sun-sized star happened to line up with Icarus and the Hubble Telescope, along with the galaxy MACS J1149+2223.
The galaxy provided a powerful gravitational lens, but the wandering star ended up magnifying our image of Icarus by roughly 2,000 times.
It was an incredibly rare opportunity, according to Alex Filippenko: "For the first time ever we're seeing an individual normal star—not a supernova, gamma-ray burst, but a single stable star—at a distance of nine billion light years. These lenses are amazing cosmic telescopes."
This probably won't be the last time we're able to spot Icarus—if the stars are right, we may see it in even higher definition over the next decade.