NASA's Hubble captures image of dead disk galaxy half the size of the Milky Way but twice as massive

NASA’s Hubble Space Telescope has used gravitational lensing to capture an image of a massive disk galaxy that challenges conventional theories of galaxy formation. The disk shaped galaxy is twice as heavy as the Milky Way, but only half of its size. The galaxy is spinning twice as fast as the Milky Way. The stars are closer together, and unlike the Milky Way, the galaxy is dead and does not produce any new stars. Star formation in the compact galaxy is believed to have ceased just a few billion years after the birth of the universe in the big bang. The finding of such a galaxy from when the universe was young is not along the lines of the current scientific understanding of how galaxies form and evolve. Astronomers expected to see a chaotic ball of stars from two colliding galaxies, but instead saw that the stars in the galaxies had formed in a flat disk shape. Sune Toft, the leader of the study says “This new insight may force us to rethink the whole cosmological context 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.” Why the galaxy stopped forming stars is unknown, and indicates that the gas is not cool enough to allow for the formation of star forming clouds, or stellar nurseries. Possible explanation include an energetic active galactic nuclei where a supermassive blackhole is heating up the gas or expelling it from the galaxy. Another explanation is that the cold gas streaming into the galaxy is getting compressed and heating up. The findings have been published in Nature.