If you check out the above artist's rendering of how we think the Milky Way would look if viewed from on high by some godlike entity, you can see that our galaxy's outer spiral arms aren't perfect, consistent lines. Rather they're broken in spots by what look like some sort of ripples. New research suggests those characteristic ripples could be the result of a dwarf galaxy made up of mostly mysterious dark matter crashing into ours hundreds of millions of years ago.
The Antlia 2 dwarf galaxy was only recently discovered in data from the. Sukanya Chakrabarti, an assistant professor at the Rochester Institute of Technology, used the data to calculate the dark little galaxy's path through the cosmos over the eons and found that it would've barreled through the Milky Way, creating the ripples visible in the outer disc.
Chakrabarti had predicted the existence of such a dark matter-dominated small galaxy back in 2009, through data analysis. She presented her new findings at a meeting of the American Astronomical Society in St. Louis on Wednesday.
"If Antlia 2 is the dwarf galaxy we predicted, you know what its orbit had to be," she said in a release. "You know it had to come close to the galactic disc."
Gaia data has also pointed astronomers towardin the past.
In addition to providing a glimpse of our own galactic history, the discovery could shine some light on the puzzling case of what, exactly, dark matter is. Estimates vary, but astrophysicists now think as much as.
"Ultimately you could use Antlia 2 as a unique laboratory to learn about the nature of dark matter," Chakrabarti says.
She and her team are hopeful that future data releases from Gaia will provide more clarity on what Antlia 2 is, where it's been, and how it shook up our own cosmic neighborhood through its travels.