The star trail, located outside the starry spiral arms of the Milky Way’s central disk in a region called the galactic halo, is dragged along with the cosmic wake of a dwarf galaxy orbiting the Milky Way, according to one new sky map created by astronomers.The galaxy, called the Large Magellanic Cloud (LMC), orbiting around 130,000 light years from Terre and stirring the wake of cosmic matter behind it. At first glance, the LMC track appears to be made up of stars only, but researchers know the stars are just for the ride. They are suspended within a much larger and completely invisible presence.
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Astronomers are so interested in this ripple in space, because they think it might be made up of black matter – the mysterious non-luminous substance constituting the great majority of the matter of the universe. Predictions say dark matter, invisible and interacting with matter we can only see by gravity, should be everywhere in the galactic halo.
“We believe that this wake is made up of dark matter and that it carries stars with it, this is how we can detect it,” explains study co-author Nicolás Garavito-Camargo, doctoral student at the University of Arizona, said in a press release.
The gravitational influence of dark matter can be observed throughout the universe: it is the vital scaffolding of our galaxy, gluing stars and planets to it so that they do not fly away when the galaxy spins. Yet what exactly dark matter is, or how it behaves, remains one of the greatest mysteries in astronomy. The researchers hope that by studying the wake, they can study the dark matter, which they believe makes up the vast majority.
If the stars in the wake are like leaves floating on a pond of dark matter, how the leaves are disturbed by a boat (in this case, the LMC) can tell us a lot about the pond itself.
“You can imagine that the wake behind a boat will be different whether the boat is sailing in water or in honey,” said lead author Charlie Conroy, professor of astronomy at Harvard University. “In this case, the properties of the wake are determined by the dark matter theory that we apply. “
The group used their new map and the position of the wake to confirm a theoretical model, created by another group of researchers, of how dark matter should be distributed across the galactic halo; they’re now running tests to see which of the dark matter theories best matches the shape and location of the wake.
The map, made using data from NASA and European Space Agency (ESA) telescopes, also provides vital information about the violent future of our home galaxy. As the LMC orbits the Milky Way, the gravitational tug of dark matter in the Milky Way’s galactic halo slows it down, sending the LMC into smaller and smaller orbits. The LMC will continue to move closer to the Milky Way until, in about 2 billion years, the two collide.
The merging of two galaxies is a surprisingly common occurrence throughout the universe. The Milky Way probably merged with a small galaxy 8 billion years ago, and galaxy mergers are a major reason for the growth of all large galaxies.
“This flight of energy from a small galaxy is not only the reason why the LMC merges with the Milky Way, but also the reason why all galaxy mergers occur,” said the co-author. study Rohan Naidu, a graduate student at Harvard University. “The wake on our map is a really crisp confirmation that our base galaxy fusion picture is on point.
The researchers published their results on April 21 in the journal Nature.
Originally posted on Live Science.