MACS J1149 Lensed Star 1

spectrum. Ultraviolet light is redshifted into the visible range and the star appears reddish. In April and May 2018, The light from LS1 was magnified not only by the huge total mass of the galaxy cluster MACS J1149.5+2223—located 5 billion light-years away—but also transiently by another compact object of about three solar masses within the galaxy cluster itself that passed through the line of sight, an effect known as gravitational microlensing. The galaxy cluster magnification is probably a factor of 600, while the microlensing event, which peaked in May 2016, brightened the image by an additional factor of ~4. Because the visible light is the redshifted ultraviolet tail, the star does not appear blue to us but reddish or pink. The light observed from the star was emitted when the universe was about 30% of its current age of 13.8 billion years. Kelly suggested that similar microlensing discoveries could help them identify the earliest stars in the universe. == Name ==

The formal name MACS J1149 is a reference to MAssive Cluster Survey and the star's coordinates in the J2000 astronomical epoch. While Kelly had wanted to name the star Warhol, alluding to Andy Warhol's notion of having 15 minutes of fame, the team ended up naming the star Icarus based on the Greek mythological figure. == Astrophysical implications ==

The discovery shows that astronomers can study the oldest stars in background galaxies of the early universe by combining the strong gravitational lensing effect from galaxy clusters with gravitational microlensing events caused by compact objects in these galaxy clusters. By using these events, astronomers can study and test some models about dark matter in galaxy clusters and observe high energy events (supernovae, variable stars) in young galaxies. ==See also==