Space Telescope Science
Astronomers combined the power of a “natural lens” in space with the capability of NASA’s Hubble Space Telescope to make a surprising discovery—the first example of a compact yet massive, fast-spinning, disk-shaped galaxy that stopped making stars only a few billion years after the big bang. Researchers say that finding such a galaxy so early in the history of the universe challenges the current understanding of how massive galaxies form and evolve. Astronomers expected to see a chaotic ball of stars formed through galaxies merging together. Instead, they saw evidence that the stars were born in a pancake-shaped disk. The galaxy, called MACS 2129-1, is considered “dead” because it is no longer making stars. This new insight is forcing astronomers to rethink their theories of how galaxies burn out early on and evolve into local elliptical-shaped galaxies. “Perhaps we have been blind to the fact that early ‘dead’ galaxies could in fact be disks, simply because we haven’t been able to resolve them,” said study leader Sune Toft of the Dark Cosmology Center at the Niels Bohr Institute, University of Copenhagen.