Flicker from 9bn light years away dazzles stargazers

A STAR nine billion light years away is the most distant single star ever to be observed by astronomers.

Usually at such distances, scientists can only observe galaxies, collections of billions of stars such as our own Milky Way, or supernovas and gamma ray bursts. Beyond 100million light years, it is impossible to make out individual stars even with powerful telescopes.

In this case, a rare cosmic alignment naturally magnified the supergiant star more than 2,000 times, allowing astronomers to see it. The B-type blue supergiant star, hundreds or even thousands of times brighter than the sun, was discovered in Hubble Space Telescope images taken between April 2016 and 2017.

It could only be seen because of “gravitational lensing”, which occurs when massive galaxy clusters bend the light of objects behind them. In effect, the galaxies act as a magnifying glass that can render dim, faraway objects visible. The lensing phenomenon, predicted by Albert Einstein, is the result of a massive object bending space-time around it and forcing light beams to take a curved path.

Dr Patrick Kelly, the lead scientist who worked on the observations while at the University of California at Berkeley, said: “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.”

A report on the discovery of the star – dubbed “Icarus” by astronomers – appears in the journal Nature Astronomy.

Prof Alex Filippenko, the co-author, said: “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.”