What is dark matter, and why does this galaxy have so much of it? Find out here.
Researchers have studied dark matter for some time, but it remains a mysterious concept that has been decidedly difficult for scientists to quantify. According to a report from Discovery News, a new study has identified a “dead” galaxy that may harbor a vast reserve of this mysterious matter.
A team of researchers led by astronomer Evan Kirby of the California Institute of Technology (Caltech) in Pasadena, CA, had been studying the Triangulum II galaxy and attempted to measure its mass. They used six tracer stars circling around the center of the galaxy, and measured their speed as they orbited. The galaxy is extremely small, holding only about 1000 stars.
Researchers expected the tracer stars to move slowly around the center of the galaxy, but their findings led them to believe that there was more than meets the eye with Triangulum II.
According to Kirby, “The total mass I measured was much, 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. The ratio of dark matter to luminous matter is the highest of any galaxy we know. After I made my measurements, I was just thinking – wow.”
Kirby believes that dark matter accounts for almost 85 percent of the universe. These particles don’t interact with normal luminous matter, which suggests that we can only really perceive a small fraction of what’s around us. The only way we can tell that dark matter exists is through the gravitational force it exerts.
As the stars whipped around the galaxy’s center at breakneck speeds, it became clear that dark matter was the only plausible explanation. The research team thinks Triangulum II has a dense cloud of Weakly Interacting Massive Particles, or WIMPs. These particles are hypothetical, meaning that they carry mass but have not been observed interacting with matter. They can interact with each other, however, releasing a burst of gamma waves when they collide.
Triangulum II is a ‘dead’ galaxy, and hasn’t had the means to form stars for billions of years. As such, scientists don’t expect to find much radiation coming from the galaxy. If they are able to detect gamma-rays, they would be able to confirm the presence of WIMPs in the galaxy.
A press release from Caltech outlining the details of the study can be found here.