That source must be beyond the galaxy. And recently, astronomers have made an astounding discovery. Globular clusters are not the only groups of stars orbiting the Milk Way, there are also ultra-faint dwarf galaxies.

 

The reason why we haven’t known about these dwarf galaxies for very long, these so called ultra-faint dwarf galaxies, is that they contain just a few hundred stars, a thousand stars. So, you try to find a column of a thousand/ stars while looking through a mass of a billion stars, it is not easy. It's the needle-in-a-haystack problem. And it's only because we have the precise maps, it's precision of modern astronomy that's allowed us to discover these extremely interesting dwarf galaxies.

 

They may be illusive, but they can help to solve the mystery of what's fueling the galaxy.

 

So these dwarf galaxies are whizzing around our galaxy, they are orbiting around it. Now sometimes they get to close, and when they get too close, they get ripped apart, in fact they get eaten as some things by our galaxy.

 

This computer model shows dwarf galaxies as colored discs. Over time our galaxy at the center devours many of them, pulled in by gravity, supplying more gas and dust from which / new stars / will eventually form.

 

So in much the same way that a large city might sort of cannibalize its neighbors, the Milky Way is cannibalizing its dwarf galaxy population. 

 

Globular clusters and dwarf galaxies give an insight just how old our galaxy is, and how it's survived for so long.