Astronomers Find Evidence of Dark Matter-Filled Galaxy X
Back in 2009, astronomers inferred the existence of a small galaxy composed almost entirely of dark matter based on ripples of hydrogen gas in the Milky Way. Since then, this galaxy, dubbed "Galaxy X," has been presumed to exist, but there has never been any concrete evidence. Now, researchers from the Rochester Institute of Technology believe they have found the first "observational confirmation" of Galaxy X's existence, as they have pinpointed four of its component stars.
The paper, which was accepted for publication by peer-reviewed journal Astrophysical Journal Letters, claims that the astronomers found four relatively young stars in the constellation Norma while analyzing the near-infrared data collected by the European Southern Observatory's VISTA telescope. The discovery of these stars is significant because they are 300,000 light years away, which is well beyond the reach of the Milky Way galaxy.
"They can't be part of our galaxy because the disk of the Milky Way terminates at 48,000 light years," said co-author Sukanya Chakrabarti. "These young stars are likely the signature of this predicted galaxy."
Galaxy X was predicted by astronomers six years ago when they observed a warp in the atomic hydrogen disk of our galaxy indicated that a small satellite galaxy composed of dark matter, which is invisible but can be observed indirectly via its effect on normal matter, was causing the ripples of hydrogen. The astronomers predict that the galaxy is difficult to see as a result of dust in our galaxy and the predominance of dark matter in its composition, but the observations of the infrared light spectrum allowed the astronomers to explore regions outside our galaxy's plane that are inaccessible using visible light.
"The discovery of the Cepheid variables shows that our method of finding the location of dark-matter dominated dwarf galaxies works," said Chakrabarti. "It may help us ultimately understand what dark matter is made up of."