[RightWhale]

the dwarf Sagittarius -- which is about 10,000 times the mass of the Milky Way

That is the bothersome part. I assume that is an error, that the Milky Way is much more massive, and denser, too, than the Sagittarius Galaxy.

[petuniasevan]

Yes, that's a typo (sloppy editing).

It should be 1/10,000 times the mass of the Milky Way.

These news agencies give stories like this to their flunkies to write. The top reporters want the J. Lo circuit or the political scene, so the low man (or woman) gets the throwaway tabloid angle to cover.

They don't know diddly about the subject matter in most cases, and this is no exception.