Question: how small is a dwarf Galaxy?

David Whitworth answered on 8 Mar 2019:

This is a little hard to answer really as there is no real set definition as to what a dwarf galaxy is. Generally speaking though a dwarf galaxy will hold between 100 million to a few 10s of billions of stars, in comparison to the Milky Way which holds somewhere between 200-400billion stars. Size wise, they can be as small as 2 kpc (3.835×10^16miles) across to maybe 10-15kpc across, the Milky Way is around 50kpc across.

Our galaxy, the Milky Way has a few dwarf galaxies circling it. We have the Large and Small Magellanic Clouds (LMC and SMC), which on a clear night you can see as smudges on the sky with the naked eye. The LMC has 30 billion stars and is about 4.5 kpc in diameter, the SMC is about half the size of the LMC with several hundred million stars. There is also the Canis Major dwarf, which is the closest galaxy to the Milky Way, and that has about a billion stars, but we don’t know much about it because it is covered in dust that makes it hard to see with telescopes.