A small galaxy orbiting the outskirts of the Milky Way appears to have a giant black hole at its center, comparable to the Milky Way itself, and scientists don’t know why.
Leo I’s dwarf galaxy, about 820,000 light -years from EarthIts width is only about 2,000 light years. Until now, astronomers thought the galaxy’s mass was about 15 to 30 million times the mass of our sun. It’s small compared to Bima Sakti, which is estimated to weigh as much as 1.5 trillion suns and have a disk width of more than 100,000 light years.
Unexpectedly, in the heart of my little lion sits Black hole A new study finds that this size is close to the size found throughout the Milky Way’s core. This discovery was contrary to expectations because astronomers believed that giant black holes grew from collisions between galaxies and must match the size of galaxies.
“There is no explanation for this type of black hole in spherical dwarf galaxies,” said Maria Jose Bustamante, a doctoral graduate in astronomy at the University of Texas at Austin and lead author of the new research paper. in the current situation.
The discovery came by chance. Scientists initially set out to measure the amount of dark matter in Leo I using the Virus-W instrument on the University of Texas’ 2.7-meter Harlan Telescope. Virus-W measures the movement of stars in the small galaxy around the Milky Way and deduces the number dark matter In the galaxies of that movement. Dark matter is a mysterious and invisible substance that resists forces gravity. Scientists can measure its concentration in the universe based on its effect on the orbits and velocities of nearby stars. The more dark matter in a star’s orbit, the faster it can move.
When the team ran the data collected in the observations through their computer model, they found that Leo I appeared to have essentially no dark matter but a black hole at its center as large as 3 million suns. (NS Sagittarius A* The black hole at the center of the Milky Way is only 25% larger).
“You have a very small galaxy falling into the Milky Way, and a black hole as big as the Milky Way,” said Carl Gebhardt, an astrophysicist at the University of Texas, Austin, and co-author of the new study. statement. “The mass ratio is huge.”
In the statement, the astronomers acknowledged that the results differed from previous dark matter calculations in the Leo I galaxy. They said previous research was based on less accurate data and did not have access to a powerful supercomputer like the Austin team.
In previous studies, scientists did not look at the densest interior regions of galaxies and focused mostly on accessible information about a few individual stars. However, this data set appears to contain a disproportionate number of slow stars. Then calculations based on this biased data set failed to detect dark matter in the interior. In the case of Leo I, the amount of dark matter in the previously invisible central region appears to be much higher than in the periphery.
learn It was published December 1 in The Astrophysical Journal.