Satellite galaxy
From Tardis Wiki, the free Doctor Who reference
Satellite galaxies, also called dwarf galaxies, were small galaxies that orbited larger galaxies. They contained many stars, but not as many as a larger galaxy.
Mutter's Spiral had a satellite galaxy called the Sculptor Dwarf galaxy or Galaxy Seven. (NSA: The Eyeless) It also had the two Magellanic Clouds, called the Larger Magellanic Cloud and Smaller Magellanic Cloud. (AG: The Last Voyage)
In the 43rd century, humans colonised the Canis Major Dwarf galaxy. (DWBIT: #45)
