Astronomers have found a large halo of dark matter surrounding a recently discovered satellite galaxy of our Milky Way.

The satellite galaxy is called Tucana 2 and it is just 1,300 light-years across, making it about 100 times smaller than our own galaxy. Tucana 2 is unique because its stars are considered to be ‘metal-poor’ which means the stars are made up of mostly Hydrogen. It is thought these hydrogen-rich stars formed very early in the universe’s history, making Tucana 2 a very old galaxy.

Astronomers determined that the galaxy has a dark matter halo by observing stars that were not near the galaxy’s center. The astronomers came to the conclusion that dark matter is what’s keeping the galaxy together and preventing those far-off stars from drifting away.

Our galaxy has 59 satellite galaxies in orbit. You can find out more about the galaxies that orbit our galaxy in this Wikipedia article