Massive, 'Dead' Galaxy Puzzles Astronomers

This artist’s concept shows the Milky Way and MACS 2129-1 side by side. MACS 2129-1 is only half the Milky Way’s size, but it’s three times as massive as our home galaxy. (Credit: NASA/ESA/Z.Levy/STScl) Objects in the distant universe appear small and difficult to see – unless they’re sitting behind a cosmic magnifying glass. That’s exactly the case for MACS 2129-1, a galaxy lensed by a massive foreground galaxy cluster. Using the Hubble Space Telescope, astronomers have managed to catch a glimpse of this unusual object, which appears to be an old, “dead” galaxy that’s already stopped making new stars just a few billion years after the Big Bang. Not only is this galaxy finished with its star formation earlier than expected, it’s also shaped like a disk, rather than the fuzzy ball of stars that astronomers assumed they’d see. The results, which were published Thursday in the journal Nature, ...