Most distant star even seen spotted nine billion light years away by astronomers

A rare cosmological phenomenon allowed astronomers to spot the star
PA
Ella Wills2 April 2018

Astronomers have found the most distant star ever discovered - a blue "supergiant" nine billion light years away.

The newly-discovered star existed when the Universe was around 30 per cent its current age, about 4.4 billion years after the Big Bang.

Named Lensed Star 1 (LS1), the hot blue star was only visible to scientists due to a rare cosmic alignment that magnified it more than 2,000 times.

Usually at such distances scientists can only image galaxies, collections of billions of stars such as our own Milky Way, or supernovas and gamma ray bursts, colossal cosmic explosions.

Beyond about 100 million light years it is impossible to make out individual stars even with the most powerful telescopes.

This image shows a huge galaxy cluster, with the position where the star LS1 appeared highlighted in red
NASA/ESA

The B-type blue supergiant star, hundreds or even thousands of times brighter than the sun, was discovered in Hubble Space Telescope images taken in April and October 2016.

The international team, led by Dr Patrick Kelly of the University of Minnesota, Dr Jose Diego of Spain's Instituto de Física de Cantabria and Dr Steven Rodney of the University of South Carolina, said the star could only be seen because of an effect called "gravitational lensing".

Light from LS1 was magnified by massive galaxy clusters that bend the light of objects behind them.

In effect the galaxies act as a magnifying glass that can render dim far away 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.

The new discovery provides insight into the formation and evolution of stars in the early Universe, the constituents of galaxy clusters and also on the nature of dark matter, the researchers said.

Lead scientist Dr Kelly 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."

The star has the long formal name MACS J1149 Lensed Star 1 (LS1), but has been dubbed "Icarus" by the astronomers.

A report on its discovery appears in the journal Nature Astronomy.

Co-author Professor Alex Filippenko, also from the University of California at Berkeley, 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.

"These lenses are amazing cosmic telescopes."

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