A tiny nearby galaxy is home to a shockingly enormous black hole

One of the Milky Way's smallest galactic neighbours seems to have a supermassive black hole at its centre, upending assumptions that it was dominated by dark matter A nearby galaxy once thought to be dominated by dark matter seems to have a surprise supermassive black hole at its centre. Segue 1 is barely a galaxy, with only about 1000 stars compared to the Milky Way's hundreds of billions, and yet it appears to be home to a black hole about 10 times as massive as all its stars combined. Segue 1 and other similar dwarf galaxies do not have enough stars to provide the gravity needed to hold them all together. To solve that problem, physicists have long assumed they were chock-full of the mysterious substance called dark matter, which we can't see but that could generate the extra gravity. So when Nathaniel Lujan at the University of Texas at San Antonio and his colleagues began testing computer models of Segue 1, they expected the best-fitting model would be one dominated by dark matter.