Two Milky Way satellite galaxies collide

The Carina Nebula is a large bright nebula that surrounds several clusters of stars. It contains two of the most massive and luminous stars in our Milky Way galaxy. Photo by ESO/IDA/Danish 1.5 m/R.Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron/ ESO/Wikicommons

Oct. 29 (UPI) — Two Milky Way satellite galaxies, the Small Magellanic Cloud and the Large Magellanic Cloud, collided a few millions years ago, according to a new study by University of Michigan astronomers.

Using new images collected by a powerful, orbiting telescope, University of Michigan astronomers noticed the southeast region, or “wing,” of the Small Magellanic Cloud breaking off from its dwarf galaxy.

Sally Oey, University of Michigan professor of astronomy, and undergraduate researcher Johnny Dorigo Jones worked with an international team of researchers to examine chunks of stars called “runaways” that had been ejected within SMC. This data came from Gaia, an orbiting telescope launched by the European Space Agency.

“It’s really interesting that Gaia obtained the proper motions of these stars. These motions contain everything we’re looking at,” Jones said in a UM press release. “For example, if we observe someone walking in the cabin of an airplane in flight, the motion we see contains that of the plane, as well as the much slower motion of the person walking.”

Gaia can plot the movement of stars in real time by imaging stars repeatedly for several years. This allows astronomers to measure how stars travel across the sky.

This provided the first conclusive evidence that the Small and Large Magellanic Clouds recently collided.

Analyzing the galaxy in this way helps astronomers give a complete sample of stars in a lone parent galaxy and it helps them measure the velocity of those stars.

“This is really one of our exciting results,” Oey said in the release. “You can actually see that the Wing is its own separate region that’s moving away from the rest of the SMC.”


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