One of the models for star and galaxy formation expects large galaxies like the Milky Way to have hundreds of smaller galaxies. Until recently we've only observed a few. The more popular "dwarf" galaxies orbiting the Milky Way Galaxy are the Large and Small Magellanic Clouds.
Earlier this year astronomers found ultra-faint galaxies which seemed to be a different class. These were dubbed "Hobbit" Galaxies. A report back in January said:
"Seven of the new galaxies are gravitationally bound to the Milky Way, while the eighth appears to float freely in space, beyond our galaxy's grasp."
I wonder how someone can tell that a small galaxy is floating freely in space. Does this mean it is far from the Milky Way Galaxy? With the short amount of time we've been able to observe these galaxies it would seem impossible to predict an orbit.
USA Today has an article which reports several astronomers measured these Hobbit Galaxies and found them to be 10,000 times smaller than the Milky Way, but it appears the mass of the Hobbit Galaxies are 100 more than would be expected for the size. This implies the Hobbit Galaxies have a higher concentration of dark matter than larger galaxies.
It will be interesting to see what develops as astronomers study the Hobbit Galaxies.
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