Half as Much Mysterious Dark Matter Exists in Our Galaxy As Previously Thought

It turns out that there may not be nearly as much dark matter in the Milky Way as scientists thought. New measurements have shown that there is about half as much as this mysterious substance in the galaxy as previously estimated.

In order to discover how much dark matter is located in our galaxy, astronomers used a method to discover the weight of dark matter. More specifically, the researchers measured the mass of dark matter by studying the speed of stars throughout the galaxy, including the edges, which had never been studied in detail before.

"The current idea of galaxy formation and evolution, called the Lambda Cold Dark Matter theory, predicts that there should be a handful of big satellite galaxies around the Milky Way that are visible with the naked eye, but we don't see that," said Prajwal Kafle, one of the researchers, in a news release. "When you use our measurement of the mass of the dark matter the theory predicts that there should only be three satellite galaxies out there, which is exactly what we see; the Large Magellanic Cloud, the Small Magellanic Cloud and the Sagittarius Dwarf Galaxy."

In this case, the researchers found that the weight of dark matter in the Milky Way galaxy is 8 x 1011 times the mass of our sun. While this may seem like a lot, though, it's only about half of what was previously estimated.

"Stars, dust, you and me, all the things that we see, only make up about four percent of the entire universe," said Kafle. "About 25 percent is dark matter and the rest is dark energy."

The findings reveal a bit more about our galaxy and the universe as a whole. The fact that far less dark matter exists shows a bit more about the physics of the Milky Way.

The findings are published in the Astrophysical Journal.