Scientists discovered highest concentration of dark matter in any known galaxy in our solar system's neighborhood.
Dark matter has never been directly observed, but its high mass allows it to have a huge gravitational influence on other objects, which researchers can then measure, Caltech reported. Now, a team of scientists has found staggering amounts of dark matter in a nearby dwarf galaxy called Triangulum II. The small, faint galaxy is located at the edge of the Milky Way.
"The galaxy is challenging to look at," said Assistant Professor of Astronomy Evan Kirby. "Only six of its stars were luminous enough to see with the Keck telescope."
By measuring the velocity of these stars, the researchers were able to determine the galaxy's mass. The total mass of the galaxy turned out to be much higher than the mass of the number of stars it contained, suggesting the presence of large quantities of dark matter.
"The ratio of dark matter to luminous matter is the highest of any galaxy we know. After I had made my measurements, I was just thinking-wow," Kirby said.
Triangulum II could potentially be used to directly detect signatures of dark matter. Particles of dark matter called supersymmetric WIMPs (weakly interacting massive particles) are believed to destroy one another as they collide, producing detectable gamma rays. Many modern theories suggest dark matter is producing gamma rays almost everywhere in the universe, but pinpointing these emissions has been a challenge. Since Triangulum II is a relatively "quiet" galaxy that is no longer producing stars, researchers could more easily detect gamma rays caused by dark matter.
Another group of researchers from the University of Strasbourg in France measured the velocities of stars just outside Triangulum II and found they are moving faster than those near the galaxy's center. This could mean galaxy is being ripped apart, or "tidally disrupted," by the Milky Way's gravity.
"My next steps are to make measurements to confirm that other group's findings," Kirby said. "If it turns out that those outer stars aren't actually moving faster than the inner ones, then the galaxy could be in what's called dynamic equilibrium. That would make it the most excellent candidate for detecting dark matter with gamma rays."
The findings were published in a recent edition of the Astrophysical Journal Letters.