An artist's illustration showing an enormous halo of hot gas (in blue) around the Milky Way galaxy (Photo : Reuters)
Galaxies, much like humans, embrace chaos in their youth, and stabilize over time as they grow, according to astronomers.
In a recent study published in The Astrophysical Journal, Susan Kassin of NASA's Goddard Space Flight Center and her team detail that galaxies exhibit constant, yet slow change, showing sings of increased rotation speed and organziation from the moment of their inception until present day.
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Kassin explains, "Astronomers thought disk galaxies in the nearby universe had settled into their present form by about 8 billion years ago, with little additional development since. The trend we've observed instead shows the opposite, that galaxies were steadily changing over this time period."
Out of the 544 blue galaxies that were analyzed, researchers found that the larger systems displayed more orderly orbits than infant galaxies.
Assistant Astronomer at the UA Steward Observatory and study co-author Benjamin Weiner states, "When we look back very far into the distant past of the universe, we find star-forming galaxies, but they don't look like our Milky Way, with its slowly rotating, orderly spiral disk-shape. Instead, those earlier galaxies appear less organized, and they show more random motion, with stars, dust and gas moving up and down and sideways within the galaxy."
Weiner notes that one of the limiting factors of past efforts to study the universe was that "previous studies removed galaxies that did not look like the well-ordered rotating disks now common in the universe today. By neglecting them, these studies examined only those rare galaxies in the distant universe that are well-behaved and concluded that galaxies didn't change. It's like looking at a bunch of adults, but you want to look at them as teenagers. We want to look at galaxies when they were young."
He adds, "It wasn't clear how galaxies settle down into their present, more orderly states. We now know it's a gradual rather than a sudden process, and it happens the same for large and small galaxies."