The oldest disk galaxy yet found formed more than 12 billion years ago
The oldest disk-shaped galaxy ever spotted formed just 1.5 billion years after the Big Bang, a new study finds. That’s much earlier than astronomers thought that this type of galaxy could form. Previous observations show that disk-shaped galaxies — including sprawling, spiral systems like the Milky Way — didn’t show up in large numbers until between 3 and 4 billion years after the Big Bang, which occurred about 13.8 billion years ago. This precocious galaxy’s existence suggests that massive spiral galaxies like the Milky Way can grow up relatively quickly, astronomers report in the May 21 Nature. By showing that a disk galaxy could form so early in the universe’s history, the new study “challenges the accepted paradigm for how disk galaxies form and evolve in the universe,” says astrophysicist Rachel Somerville of the Flatiron Institute in New York City, who was not involved in the study. The earliest galaxies probably were made when clumps of invisible dark matter pulled in surrounding gas and dust,...