Picture of the month

Although barely noticeable in this image of a massive galaxy cluster (left), which was taken with the Hubble Space Telescope, the small blue dot in the centre of the inset could be the farthest star ever observed. The source appeared to come out of nowhere: it was visible in 2016 (bottom right) but not in 2011 (top right). Such transients are typically associated with supernovae, but the spectrum and variability of the source seem to agree much more with those of a distant blue supergiant star magnified 2000 times by the gravitational lensing of the foreground galaxy cluster. If this interpretation is correct, the star, now called Icarus, would be the farthest star ever seen, with a light-travel distance of about nine billion light years.

About the author

Compiled by Merlin Kole, Department of Particle Physics, University of Geneva.