UC Berkeley researchers discover farthest star ever observed, 9 billion light years away

NASA, ESA, P. Kelly (Univ. Minnesota)/Courtesy

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The most distant star ever observed — at a distance of about nine billion light years — was captured using the Hubble Space Telescope by a group of researchers, including members of the UC Berkeley department of astronomy.

The star, named MACS J1149 Lensed Star 1, or LS1, was observed in April 2016 when researchers were examining images of a distant supernova, according to campus astronomy professor Alex Filippenko.

“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,” Filippenko said in a press release Monday.

Patrick Kelly, study leader and assistant astronomy professor at the University of Minnesota, Twin Cities, said he noticed there was a new source in the image and put together a large team to figure out what it was.

The star would not have been visible under normal circumstances because it is difficult to distinguish individual stars in distant galaxies beyond 100 million light years, but the position of this galaxy allowed for the viewing of the star, according to Kelly.

The effects of gravitational lensing — the bending of light by galaxy clusters in the line of sight — can magnify the distant universe and make faraway objects visible, according to the press release. Filippenko said in an email that this particular star was magnified by a factor of at least 2,000, making it visible in the telescope.

“The source isn’t getting hotter; it’s not exploding. The light is just being magnified,” Kelly said in a NASA statement. “And that’s what you expect from gravitational lensing.”

Kelly added that LS1 is 100 times farther away than the most distant stars previously observed, which can open up the universe to new techniques of observation.  

“When we found it, another star moved into just the right place that caused it to brighten,” Kelly said. “When we can pick out individual stars, we can learn a lot more about the makeup of galaxies and clusters of galaxies.”

Kelly said researchers anticipate being able to observe stars at greater distances using the James Webb Space Telescope, which can collect 10 times as many photons — and can pick up objects 10 times as distant — as the Hubble Space Telescope can.

The supernova that was initially observed was a blue supergiant star, and LS1 is also a blue supergiant that is 1 million times as luminous and two times as hot as the sun. Kelly also added that the star is likely dead now, but observers can still learn from its properties.

“This star lets us, essentially, look nine billion years into the past, and with new telescopes like the Webb Telescope, we can look back even farther,” Kelly said.

Contact Amanda Bradford at [email protected] and follow her on Twitter at @amandabrad_uc.