Astronomers from the US Berkeley University have detected a star with a Hubble space telescope using a gravitational lens that is about nine billion light-years from Earth. This is the farthest star ever detected.
According to one of the astronomers the discovered star is at least one hundred times as far away as the second-to-last individual star that can be studied. The discovery of this star, called Icarus, is quite special, because it is so far away that it would normally not be noticed. Only very bright objects, such as supernovas or galaxies, can still be detected at distances of nine billion light-years from the earth.
The discovery of Icarus, which was done in 2016, was possible because of the gravitational lens effect of a cluster of galaxies that is located five billion light-years from Earth. Such clusters usually cause a factor fifty to be amplified, but a specific star from the cluster provided a short gain of two thousand times.
Individual stars or galaxies can amplify the light of stars behind when they are exactly in line, making them work like a lens. The passing star caused by its gravity a so-called Einsteinring a sort of ring of light that is bent around the object by gravity. This ring is too small to be detected, but the effect did strengthen the brightness of the star, making it visible.
According to the researchers, Icarus, which is located in a spiral galaxy, is a so-called blue superstar that is much larger. heavier, hotter and probably a hundred to several thousand times brighter than our sun. The astronomers think that the light of the star will be amplified even more in the next ten years, because more clusters of stars will pass in front of Icarus, possibly involving a reinforcement of about ten thousand times.
The discovery has been published in the scientific journal Nature Astronomy, under the title “Extreme magnification of an individual star at redshift 1.5 by a galaxy-cluster lens.”
On the left is the cluster of galaxies in the square , called MACS J1149 + 2223. Right is Icarus, or MACS J1149 + 2223 Lensed Star 1, which was not visible in 2011 but in 2016.