astronomers find new evidence that galaxies like our own milky way may not have grown so big so early out therea vast wheel of gas in the primordial cosmos is forcing astronomers to rethink how some of the universes largest structures may have formedcreditnraoauinsf s dagnellopublished may 20 2020updated may 25 2020in the early days of the hubble space telescope astronomers eager to see how far out in space and how far back in time their new instrument could peer pointed it at an empty tract of sky what returned was an image of space littered with what the astronomer alan dressler of the carnegie observatories called train wrecks irregular fragmented clouds of stars known as protogalaxies flecks of starlight scattered like orphan jigsaw puzzle pieces across the primordial heavensthe scene fit nicely with the growing consensus of how the universe had evolved over cosmic time small bits of matter gas dust and starlight slowly assembled themselves into ever larger structures eventually resulting in majestic spiral galaxies like our own milky way 100000 lightyears across and home to hundreds of billions of starsbut a new discovery suggests that this vision of cosmic growth may need revision on wednesday radio astronomers using the mighty atacama large millimeter array or alma radio telescope in chile announced that they had discovered a cloud of gas located on the distant shores of time it appears to be an infant galaxy similar in size to its grownup counterpart our own milky way and dates to a time when the universe was only 15 billion years old onetenth its current agethe galaxy known formally as alma j081740861351382 after its coordinates in the sky is a giant rotating wheel of gas dust and faint starlight a socalled disk galaxy that extends 100000 lightyears across the primordial sky it is at least as massive as 70 or 80 billion suns in the same weight class as the milky wayto see it is a surprise said j xavier prochaska of the university of california santa cruz one of the authors of a paper published in nature describing the discoveryconventional lore held that such disk galaxies could not grow so big so early most galaxies that we find early in the universe look like train wrecks because they underwent consistent and often violent merging marcel neeleman of the max planck institute for astronomy in heidelberg germany and lead author of the paper said in a statement released by the institute these hot mergers make it difficult to form wellordered cold rotating disks like we observe in our present universein an interview dr prochaska said that train wrecks still make up 90 percent of the action in the very early universe but the discovery of this galaxy suggests that large rotating disks were also part of the primordial mix and that astronomers will most likely find more of them he said if that is the case astronomers will need to modify some of their theories of how galaxies came to bedr