One of these things is not like the other: Astronomers have
spotted a dwarf galaxy that spans just 3,000 light years across
(as opposed to our Milky Way’s diameter of 100,000 light years),
but hosts an outsize supermassive black hole for its puny size.
Some smaller galaxies have supermassive black holes as well, but
in general these dwarf galaxies have some structure to them,
with a well-defined core. Henize 2-10, as you can see, it a
mess! It doesn’t have much overall structure, which is why it’s
classified as an irregular galaxy. The thinking for big galaxies
is that the black hole forms at the same time as the galaxy
itself, and to regulate the growth of each other. When you look
at lots of big galaxies, there’s a pretty clear overall
correlation between the mass of the black hole and the galaxy
around it. So it’s pretty weird that Henize 2-10 has a
supermassive black hole at all, but it turns out the hole is
also about a million times the mass of the Sun — that’s pretty
freakin’ big for such a tiny galaxy