Dark Matter, The mysterious, unidentified substance thought to make up most of the matter in the Universe, is much less dominant in our Galaxy than astronomers thought.
A new study hints there is only about half as much as earlier predictions suggested. Dark matter is invisible to telescopes but astronomers can tell that it’s there due to its gravitational influence on the motions of stars. To measure the amount of dark matter in the Milky Way, a team led by Prajwal Kafle from the University of Western Australia mined data from sky surveys to measure star speeds up to about 5 million trillion km away.
Their results suggest our Galaxy contains 800 billion solar masses of dark matter, much less than previously estimated. This low figure could help explain why there are fewer large satellite galaxies of the Milky Way visible to the naked eye than might be expected. “When you use our measurement of dark matter, theory predicts that there should only be three satellite galaxies out there, which is exactly what we see,” says Kafle.