Observation of a similar galaxy to ours shows the Milky Way likely formed naturally rather than the result of a collision with a smaller galaxy.
(CN) — Long thought to be the product of a collision with another galaxy, new research released Monday casts doubt on how the Milky Way was formed.
In a study published in The Astrophysical Journal Letters, Australian scientists created the first detailed cross-section of UGC 10738, a galaxy similar to our own. From that model, they discovered that the Milky Way formed gradually, rather than the result of an encounter with a smaller galaxy.
Making use of the European Southern Observatory’s Very Large Telescope in Chile, researchers were able to analyze the distant galaxy located 320 million light years from our own. UGC 10738, like the Milky Way, has “thick” and “thin” discs that astronomers have previously theorized to be the effect of galaxies colliding. Instead, according to Monday’s study, they are a natural part of a galaxy’s formation.
“Our observations indicate that the Milky Way’s thin and thick discs didn’t come about because of a gigantic mash-up, but a sort-of ‘default’ path of galaxy formation and evolution,” said Nicholas Scott from the University of Sydney in a statement. “From these results we think galaxies with the Milky Way’s particular structures and properties could be described as the ‘normal’ ones.”
Scott said the Milky Way’s discs “formed after a rare violent merger, and so probably wouldn’t be found in other spiral galaxies.”
“Our research shows that’s probably wrong, and it evolved ‘naturally’ without catastrophic interventions. This means Milky Way-type galaxies are probably very common,” Scott said. “It also means we can use existing very detailed observations of the Milky Way as tools to better analyse much more distant galaxies which, for obvious reasons, we can’t see as well.”
According to the research team’s analysis, UGC 10738 has a thick disc made up primarily of ancient stars. While other galaxies have such discs, astronomers have been unable to tell if they had similar star distribution to ours.
“This is an important step forward in understanding how disk galaxies assembled long ago,” said Ken Freeman, professor at Australian National University. “We know a lot about how the Milky Way formed, but there was always the worry that the Milky Way is not a typical spiral galaxy. Now we can see that the Milky Way’s formation is fairly typical of how other disk galaxies were assembled.”