Free Astronomy Magazine November-December 2015

SPACE CHRONICLES sity, Montreal, Canada, lead author of the study. The galaxy was initially discover- ed using NASA’s Spitzer Space Tele- scope and the Canada-France-Ha- waii Telescope, located on Mauna Kea in Hawai`i and confirmed us- ing the W.M. Keck Observatory, also on Mauna Kea. Follow-up observa- tions using the NASA/ESA Hubble Space Telescope allowed the astro- nomers to explore the galaxy’s ac- tivity. The SpARCS 1049+56 cluster is so far away that its light took 9.8 bil- lion years to reach us. It houses at least 27 galaxies and has a combin- ed mass equal to 400 trillion Suns. It is a truly unique cluster in one as- pect — its vibrant heart of new stars. The cluster’s brigh- test galaxy is rap- idly spitting out 800 new stars per year. The Milky Way forms two stars per year at most! (At the core of most galaxy clusters lies a hulking galaxy called the brigh- test cluster galaxy, or BCG. This newly discovered starbur- sting galaxy is the BCG in SpARCS1049 +56.) “The Spitzer data showed us a Astronomers find galaxy cluster with bursting heart G alaxy clusters are vast families of galaxies bound together by gravity. Our own galaxy, the Milky Way resides within a small gal- axy group known as the Local Group, which itself is a member of the massive Laniakea supercluster. Gal- axies at the centres of clusters are usu- ally made of stellar fossils — old, red or dead stars. However, astrono- mers have now dis- covered a giant galaxy at the heart of a cluster named SpARCS1049+56 that seems to be bucking the trend, instead forming new stars at an in- credible rate. “We think the giant gal- axy at the centre of this cluster is furiously making new stars after merging with a smaller galaxy,” ex- plained Tracy Webb of McGill Univer- by NASA T his image, made with data obtained through Spitzer and the Hub- ble Space Telescope, shows the galaxy cluster SpARCS1049+56. [NASA/STScI/ESA/JPL-Caltech/McGill]