Free Astronomy Magazine May-June 2015

SPACE CHRONICLES Hubble sees supernova split into four images by cosmic lens by NASA light-years from Earth. The super- nova behind it is 9.3 billion light- years away. Although astronomers have discov- ered dozens of multiply imaged gal- axies and quasars, they have never seen a stellar explosion resolved in- to several images. "It re- ally threw me for a loop when I spotted the four images surrounding the galaxy — it was a com- plete surprise," said Pat- rick Kelly of the Univer- sity of California, Berke- ley, a member of the Grism Lens Amplified Sur- vey from Space (GLASS) collaboration. The GLASS group is working with the Frontier Field Supernova (FrontierSN) team to ana- lyze the exploding star. Kelly is also the lead au- thor on the science paper appeared on March 6 in a special issue of the jour- nal Science celebrating the centenary of Albert Einstein's Theory of Gen- eral Relativity. When the four images fade away, astronomers predict they will have a rare opportunity to catch a rerun of the supernova. This is because the cur- rent four-image pattern is only one part of the axy in a cross-shaped pattern called an Einstein Cross, a name originally given to a particular multiply im- aged quasar, the bright core of an active galaxy. The elliptical galaxy and its cluster, MACS J1149.6+2223, are 5 billion A stronomers using NASA's Hub- ble Space Telescope have spot- ted for the first time a distant supernova split into four images. The multiple images of the exploding star are caused by the powerful gravity of a foreground ellipti- cal galaxy embedded in a massive cluster of gala- xies. This unique observa- tion will help astrono- mers refine their esti- mates of the amount and distribution of dark mat- ter in the lensing galaxy and cluster. Dark matter cannot be seen directly but is believed to make up most of the universe's mass. The gravity from both the elliptical galaxy and the galaxy cluster distorts and magnifies the light from the supernova be- hind them, an effect cal- led gravitational lensing. First predicted by Albert Einstein, this effect is sim- ilar to a glass lens bend- ing light to magnify and distort the image of an object behind it. The mul- tiple images are arranged around the elliptical gal- T his image shows the huge galaxy cluster MACS J1149.6 +2223, whose light took over 5 billion years to reach us. [NASA, ESA, S. Rodney (John Hopkins University, USA) and the FrontierSN team; T. Treu (University of California Los Angeles, USA), P. Kelly (University of California Berkeley, USA) and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)]