Ripples in the outer reaches of the Milky Way may originate from our galaxy's collision with a puzzlingly faint galaxy called Antlia 2, a new study has found.
Antlia 2 was discovered in 2018 by the European Space Agency's Gaia satellite. The galaxy's dimness and sparseness of stars suggests that it is held together by a lot of dark matter. Unlike normal matter, which makes up everything that we can see including planets and stars, dark matter is a mysterious, invisible substance that has never been directly detected.
In 2009, Sukanya Chakrabarti of Rochester Institute of Technology had predicted that a dark-matter dominated galaxy would be in the location of Antlia 2. Using recent Gaia data, Chakrabarti and colleagues then calculated this galaxy's past trajectory, and found that Antlia 2 crashed into the Milky Way several hundred million years ago. This collision could have produced the large ripples that we see in the outer gas disc of the Milky Way today.
This discovery could help astronomers look for other dark galaxies and explore dark matter. "Ultimately you could use Antlia 2 as a unique laboratory to learn about the nature of dark matter,” Chakrabarti said.
The research, presented at the American Astronomical Society meeting in Saint Louis, Missouri, was supported by grants from NASA and the National Science Foundation.
Written by Elizabeth Landau
NASA Headquarters
Last Updated: June 12, 2019
Editor: Sarah Loff
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