Although there are several theories about the nature of dark matter, all of them suggest that it should occur in the Milky Way. If this is the case, the LMC must also sail through the region, but also into the dark matter. The waking observed in the new star map is presumably the outline of this waking dark matter; the stars are like leaves on the surface of this invisible ocean, and their position shifts with the dark matter.
The interaction between dark matter and the Large Magellanic Cloud has major implications for our galaxy. As the LMC orbits the Milky Way, the gravity of the dark matter drags to the LMC and slows it down. This will cause the orbit of the dwarf system to become smaller until the galaxy finally collides with the Milky Way in about 2 billion years. These types of mergers can be a major driver in the growth of massive galaxies across the universe. Astronomers think that the Milky Way merged with another small galaxy about ten billion years ago.
‘The robbery of the energy of a smaller galaxy is not only the reason why the LMC merges with the Milky Way, but also why everyone mergers of galaxies happen, ”said Rohan Naidu, a doctoral student in astronomy at Harvard University and co-author of the new article. “The aftermath of our map is a neat confirmation that our basic picture of how galaxies are merging is on point!”
A rare opportunity
The authors of the article also think that the new map – together with additional data and theoretical analyzes – can provide a test for different theories about the nature of dark matter, such as whether it consists of particles, such as ordinary matter, and what the properties are. of those particles are.
“You can imagine that waking up behind a boat would be different than sailing through water or honey,” said Charlie Conroy, a professor at Harvard University and an astronomer at the Center for Astrophysics | Harvard & Smithsonian, who co-authored the study. “In this case, the properties of the aftermath are determined by the dark matter theory we apply.”
Conroy led the team that mapped the positions of more than 1,300 stars in the ray chart. The challenge arose to measure the exact distance of the earth from a large part of the stars: it is often impossible to determine whether a star is faint and near or bright and far away. The team used data from ESA’s Gaia mission, which provides the location of many stars in the sky but cannot measure the distance to the stars in the outer regions of the Milky Way.
After identifying stars that are likely to be located in the halo (because they were not naturally in our galaxy or the LMC), the team searched for stars that belong to a class of giant stars with a specific light “signature” which can be detected by NEOWISE. The knowledge of the basic properties of the selected stars enabled the team to determine their distance from the earth and create the new map. It maps a region that begins approximately 200,000 light-years from the center of the Milky Way, or where the forecast of the LMC would begin, and extends approximately 125,000 light-years beyond.
Conroy and his colleagues were inspired to be on the lookout for LMC after learning about a team of astrophysicists at the University of Arizona in Tucson who had computer models predict how dark matter should look in the galactic halo. The two groups collaborated on the new study.
One model of the Arizona team, included in the new study, predicted the general structure and specific location of the stargazer on the new map. After the data confirmed that the model was correct, the team was able to confirm what other investigations also indicated: that the LMC is probably on its first orbit around the Milky Way. If the smaller galaxy had already made several orbits, the shape and location of the orbit would differ significantly from what was observed. Astronomers think that the LMC formed in the same environment as the Milky Way and another nearby galaxy, M31, and that it is close to completing a long first orbit around our galaxy (about 13 billion years). The next lane will be much shorter due to the interaction with the Milky Way.
“Confirming our theoretical prediction with observational data tells us that our understanding of the interaction between these two galaxies, including dark matter, is on track,” said Nicolás Garavito-Camargo, PhD student in astronomy at the University of Arizona. which led the work to the model used in the paper.
The new map also offers astronomers a rare opportunity to test the properties of dark matter (the supposed water or honey) in our own galaxy. In the new study, Garavito-Camargo and colleagues used a popular dark matter theory called cold dark matter that fits the observed star map relatively well. The University of Arizona team is currently working on simulations that use different theories about dark matter to see which one best fits the aftermath in the stars.
“It’s a very special set of circumstances put together to create this scenario that allows us to test our theories about dark matter,” said Gurtina Besla, an associate author of the study and associate professor at the University of Arizona, said. “But we can only realize the test with the combination of this new map and the symptoms of dark matter we have built.”
The WISE spacecraft, launched in 2009, was put into hibernation in 2011 after completing its primary mission. In September 2013, NASA reactivated the spacecraft with the primary purpose of searching for near-Earth objects, or NEOs, and the mission and spacecraft were renamed NEOWISE. NASA’s Jet Propulsion Laboratory in Southern California managed and managed WISE for NASA’s Directorate Science Mission. The mission was competitively selected under NASA’s Explorers program run by the agency’s Goddard Space Flight Center in Greenbelt, Maryland. NEOWISE is a project of JPL, a division of Caltech, and the University of Arizona, supported by NASA’s Planetary Defense Coordination Office.