An astronomer at the California Institute of Technology (Caltech) have discovered a ‘dead’ galaxy at the edge of the Milky Way with the highest concentration of dark matter. The small galaxy called Triangulum II has just 100 million stars, when compared to the 100 billion in our own galaxy.
In a study published in the Astrophysical Journal Letters, researchers said that the mysterious, dark matter may be responsible for the galaxy’s low star count. The study’s lead author Evan Kirby of Caltech and his team measured the mass of the galaxy by studying the velocity of six stars dashing around its center.
Kirby said that only six of its stars were luminous enough to see with the Kleck telescope, Triangulum II could become the focus of researcher’s efforts to understand how dark matter interacts with the rest of the universe. A galaxy has a mass that is measured by the amount of matter and dark matter.
“It (Traingulum II) could be an excellent candidate for indirect, gamma-ray detection of dark-matter annihilation,” said Kirby.
Caltech Assistant professor of Astronomy Kirby found that the total mass which he measured was much greater than the mass of the total number of stars–implying that there’s a ton of densely packed dark matter contributing to the total mass. Kirby mentioned that he will make measurements to confirm the other group findings. Hence, any gamma signals emitted from Triangulum’s dark matter could be easily detected. Particles called super symmetrical WIMPs emitted from the dark matter have a tendency to accumulate and collide with each other, causing gamma rays.
However, another research group explained that the small galaxy is being torn away from the Milky Way as stars on the edge of the galaxy are moving away faster than those in the middle, challenging the theory of Kirby’s study. The researchers are also studying this possibility, but they want to prove that Triangulum II is loaded with dark matter.
If the study is true, the dead galaxy could be the best subject to detect the gamma rays that certain particles of dark matter produce when they interact with one another. As Triangulum II is dead, it would be easier to pick up gamma rays, which are otherwise difficult in the noise of space. When it comes to the mysterious dark matter, it is difficult to believe as it is invisible to instruments and eyes, and occupies more of the universe than any other matter. If it turns out that those outer stars are aren’t actually moving faster than the inner ones, then the galaxy could be in what’s called a dynamic equilibrium.