The Large Magellanic Cloud (LMC) is one of the Milky Way’s closest neighbors. It’s a small, irregular galaxy that orbits the Milky Way, and is an easy naked-eye object from the Southern Hemisphere. As one of the only galaxies outside our own where telescopes can resolve individual stars and small scale structures, astronomers love to examine the LMC to compare and contrast it with the Milky Way.
While large galaxies host central supermassive black holes (SMBH) as a rule, dwarf galaxies like the LMC are more mixed. Astronomers have speculated about it containing a black hole, but the data has been inconclusive.
Now, data from the Gaia space telescope, which tracked more than a billion stars to measure their movements and positions, has pointed to a surprising addition to this object that sits right in our cosmic backyard: It appears to have a central black hole weighing 600,000 times as much as the Sun. The research, led by Jesse Jiwon Han of the Harvard-Smithsonian Center for Astrophysics (CfA), has been accepted for publication in The Astrophysical Journal.
Speedy stars
The discovery comes from a study of hypervelocity stars in the Milky Way. These are stars that, as their name indicates, are moving rapidly compared to their neighbors — up to 2.2 million miles per hour (1,000 kilometers per second), instead of cruising along with the rest of the stars in the current of the Milky Way. Astronomers thought that most of these hypervelocity stars reached those high speeds after an encounter with the Milky Way’s own central black hole, Sagittarius A*. (Such speedy stars were one of the biggest clues that led astronomers to discover and understand Sag A*.)
But when Han, a graduate student at the CfA, looked at a batch of hypervelocity stars in the Gaia data, he tracked their path back not toward the Milky Way’s core, but to the LMC.
