Astronomers at the California Institute of Technology have discovered what they claim to be the highest concentration of dark matter in any known galaxy. They found it while measuring the mass of a nearby dwarf galaxy called Triangulum II located at the edge of the Milky Way. Findings of the study were published in the latest issue of the Astrophysical Journal Letters.
Triangulum II is densely packed with dark matter
Though dark matter is estimated to account for 85% of total mass of the universe, these particles are elusive. That’s because they do not interact with the visible matter. Their presence can be felt only through their gravitational influence in galaxies. Triangulum II is a faint galaxy with only about 1,000 stars. Astronomers led by Evan Kirby of CalTech measured the mass of the galaxy by studying the velocity of six stars dashing around in its center.
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This quiet galaxy lacks the gas and other matter necessary to form new stars. That’s why astronomers called it a “dead” galaxy. Only six of its 1,000 stars were bright enough to be seen by the Keck Telescope. Astronomers were surprised to find that the total mass of the galaxy was much higher than the mass of all the stars combined. It indicates that there is a vast amount of densely packed dark matter that is contributing to the total mass.
Galactic noise makes it difficult to detect key signals
Kirby said this galaxy has the highest ratio of dark matter to luminous matter of any known galaxy. So, Triangulum II may become the center of researchers’ efforts to detect signs of dark matter. On top of that, the dead galaxy shouldn’t produce much high-energy radiation, making things easier for astronomers.
Certain dark matter particles such as the supersymmetric Weakly Interacting Massive Particles (WIMPs) carry mass but don’t interact with normal matter. These hypothetical ghostly particles annihilate one another when they collide, producing gamma rays that can be detected from Earth. Current theories predict that dark matter produces gamma rays everywhere in the universe. But it is extremely difficult to detect these signals from other galactic noise such as gamma rays from pulsars.
Triangulum II is a dead galaxy. So if we detect gamma rays there, it would most likely have been produced by WIMP annihilation.