5 Ways To Make A Galaxy With No Dark Matter
“2.) Ejected from galactic mergers. When two galaxies smash together, they usually merge entirely, but sometimes there is ejected material. Sufficient amounts could create a baryons-only galaxy.”
Last week, astronomers announced the discovery of the ultra-diffuse galaxy NGC 1052-DF2 (or DF2), which appears to be completely free of dark matter. Other similar galaxies have been seen before, but all contain more, not less, dark matter than you’d have expected on average. This first galaxy ever seen without the gravitation-altering effects of dark matter was touted to defy theory, but it does no such thing. In fact, there are many explanations that lead directly to galaxies such as DF2 as an inevitable consequence, including one that was put forth in a predictive fashion as much as 20 years ago.