NASA's Hubble Space Telescope Photographs Its Most Distant Star Ever

In May 2016, astronomers were able to look 9 billion light-years across the universe, spotting the most distant individual star ever identified: MACS J1149 Lensed Star 1 (LS1), nicknamed Icarus. To do so, according to a new paper published Monday in Nature Astronomy, they combined the power of NASA's Hubble Space Telescope with a natural effect that makes distant objects appear much brighter than usual: gravitational lensing.

"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," co-author Alex Filippenko, an astronomer at the University of California, Berkeley, said in a press release. "These lenses are amazing cosmic telescopes."

The lenses Filippenko mentions aren't fancy camera gear. Gravitational lenses are large objects in space, and gravitational lensing is the technique that magnifies distant stars and galaxies. Super-massive objects have such strong gravity that they warp the universe around them, including light, bending it the same way a magnifying glass does. That means that when the perfect galaxy passes between Earth and a target, astronomers have a brief window during which they can capture an unusually detailed picture.

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Usually, astronomers can't identify individual stars more than about 100 million light-years away. Gravitational lensing relies on good luck, but it makes stars much easier to spot, easily magnifying them about 50 times over. In this case, the star was magnified 2,000 times.

The particularly strong lensing effect created what astronomers call an Einstein ring, an unusual type of gravitational lensing in which the bent light forms a ring. The star in this case is so far away that scientists didn't actually see the Einstein ring as a ring. Instead, the phenomenon made the star bright enough to see in images taken by the Hubble Space Telescope.

An image of the star astronomers spotted from 14 billion light-years away. NASA, ESA, and P. Kelly (University of Minnesota)

"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 said in the press release. "For this type of research, nature has provided us with a larger telescope than we can possibly build!"

As those alignments shuffle around, Filippenko and his co-authors think they may be able to snag an even sharper image of Icarus, perhaps showing the star magnified five times more than it was at the peak of this magnifying event.