An ancient galaxy grew massive — then oddly stopped making stars
Even galaxies burn out if they work too hard. A galactic monster in the early universe quit forming stars after ferociously churning them out for hundreds of millions of years, researchers report. Why it slacked off is unclear, but the answer might teach astronomers a thing or two about how the earliest galaxies grew and evolved into the stellar metropolises that surround us today. The light from this galaxy, designated XMM-2599, took nearly 12 billion years to reach Earth. So astronomers see the galaxy as it was just 1.8 billion years after the Big Bang. By that time, the galaxy had bulked up to a mass of about 300 billion suns, new observations show, making it three times as massive as similar known galaxies from that epoch. The galaxy appears to have gotten so hefty by cranking out stars at a rate of over 1,000 solar masses per year for several hundred million years. But then, the star making suddenly stopped, astronomer Benjamin...