Hubble captures farthest star ever seen
The blue supergiant Icarus is spied more than 9 billion light years from Earth in an astonishing discovery
“This is the first time we’re seeing a magnified, individual star"
Astronomers using NASA's Hubble Space Telescope have detected the most distant star ever viewed. The enormous blue star, which has been nicknamed Icarus, is as much as a million-times more luminous and twice as hot as our Sun. It is located in a very distant spiral galaxy and it is so far away that its light would have taken a staggering 9 billion years to reach Earth.
According to the team leading the discovery, the blue supergiant appears to us as it did when the universe was about 30 per cent of its current age, and it is more than 100-times further away than the next individual star to have been studied. “This is the first time we’re seeing a magnified, individual star,” says study leader Patrick Kelly, a former University of California at Berkeley postdoc who now works at the University of Minnesota,
The find came as the team was monitoring a supernova in the spiral galaxy, and was made possible thanks to gravitational lensing, a quirk of nature that acts to amplify the star's feeble glow. Gravity from a massive foreground cluster of galaxies called MACS J1149+2223 acts as a natural lens, bending and amplifying light. Situated 5 million light years from Earth, the cluster sits between our planet and Icarus, and it allowed for a better – albeit fleeting – view. Indeed, it was only temporarily magnified to 2,000times its true brightness. Usually it is ‘only’ magnified by 600-times.
The team was able to rule out the source of light as being the supernova they were monitoring. “The source isn’t getting hotter; it’s not exploding. The light is just being magnified,” said Kelly. “And that’s what you expect from gravitational lensing.” Kelly has also used Icarus to test a theory of dark matter and to investigate the composition of a foreground galaxy cluster. A statement says the team probed what is floating around in the foreground cluster and appeared to rule out the theory that dark matter is made up mostly of a large number of primordial black holes formed in the birth of the universe. If that was the case, they say, then light fluctuations from the background star would have looked different.
Kelly also says that more stars like Icarus are expected to be found when the more sensitive James Webb Space Telescope is launched. The joint collaboration between NASA, ESA and the Canadian Space Agency is set to be launched in May 2020.
This composite shows the location of the most
distant known star, detected using Hubble