Gravitational Lens Reveals Most Distant Star Seen
There are stars too faint to see in the night sky just a few light years away, yet a chance cosmic event gave us a glimpse of a star that would have otherwise been completely invisible due to its immense distance from Earth-a whopping 9 billion light-years away.
A paper today in Nature Astronomy reports the discovery of the star, called MACS J1149 Lensed Star 1, or Icarus informally. Finding such a distant star is normally a tall order, but a larger object happened to pass in front of its home galaxy. When a large object passes in front of another, its gravitational well bends space around it and can act like a giant magnifying glass in the sky.
Astronomers know when they're seeing a gravitationally lensed object because of an effect called Einstein's Ring. This is a halo of light bent around the lensed object. The astronomers were already observing the lensing event with the Hubble Space Telescope to study to the supernova Refsdal, which was spotted in 2016.
Icarus is a B-type star, often called a blue giant due to the color it radiates. They're the second most massive type of main sequence star. The star's discovery is the first time a lensing event has revealed a star so distant that wasn't part of a violent stellar event.
“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,” Alex Filippenko, a professor of astronomy at UC Berkeley, said in a press release.
Astronomers also witnessed what was either a mirror image of Icarus or an unrelated star in the lensing event. The event may also repeat itself, giving astronomers the opportunity to view Icarus a few more times in the coming years.
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