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Gravitational Lensing Reveals Blue Supergiant 9 Billion Light Years Away

Gravitational Lensing Reveals Blue Supergiant 9 Billion Light Years Away Icarus, whose official name is MACS J1149+2223 Lensed Star 1, is the farthest individual star ever seen. It is only visible because it is being magnified by the gravity of a massive galaxy cluster, located about 5 billion light-years from Earth. Called MACS J1149+2223, this cluster, shown at left, sits between the Earth and the galaxy that contains the distant star. The team had been using Hubble to monitor a supernova in the far-off spiral galaxy when, in 2016, they spotted a point of light near the supernova that began to brighten. Even though the object subsequently became three times brighter in one month, the colors of the light coming from the object did not change. Analysis of these colors showed it was a blue supergiant star in the background galaxy whose magnification grew for several weeks due to an intervening object, probably a star, in the galaxy cluster. The panels at the right show the view in 2011, without Icarus visible, compared with the star's brightening in 2016. Credit: NASA, ESA, and P. Kelly, University of Minnesota Read more at: https://phys.org/news/2018-04-gravitational-lensing-sun-like-star-massive.html#jCp

Icarus, whose official name is MACS J1149+2223 Lensed Star 1, is the farthest individual star ever seen. It is only visible because it is being magnified by the gravity of a massive galaxy cluster, located about 5 billion light-years from … Thanks to a rare cosmic alignment, astronomers have captured the most distant normal star ever observed, some 9 billion light years from Earth.

While astronomers routinely study galaxies much farther away, they’re visible only because they glow with the brightness of billions of stars . And a supernova, often brighter than the galaxy in which it sits, also can be visible across the entire universe.

Beyond a distance of about 100 million light years, however, the stars in these galaxies are impossible to make out individually.

But a phenomenon called gravitational lensing – the bending of light by massive galaxy clusters in the line of sight—can magnify the distant universe and make dim, far away objects visible. Typically, lensing magnifies galaxies by up to 50 times, but in this case, the star was magnified more than 2,000 times. It was discovered in NASA Hubble Space Telescope images taken in late April of 2016 and as recently as April 2017.

“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,” said former UC Berkeley postdoctoral scholar Patrick Kelly, now on the faculty at the University of Minnesota, Twin Cities. Kelly is first author of a paper about the discovery appearing online this week in advance of publication in the journal Nature Astronomy .

The discovery of the star, which astronomers often refer to as Icarus rather than by its formal name, MACS J1149 Lensed Star 1 (LS1), kicks off a new technique for astronomers to study individual stars in galaxies formed during the earliest days of the universe. These observations can provide a rare look at how stars evolve, especially the most luminous ones.

“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,” said Alex Filippenko, a professor of astronomy at UC Berkeley and one of many co-authors of the report. “These lenses are amazing cosmic telescopes.”

 

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