Itty Bitty Galaxy Home to Gargantuan Supermassive Black Hole
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 doesnâ€™t have much overall structure, which is why itâ€™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, thereâ€™s a pretty clear overall correlation between the mass of the black hole and the galaxy around it.
So itâ€™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 â€” thatâ€™s pretty freakinâ€™ big for such a tiny galaxy! Thatâ€™s 1/4 the mass of our own black hole, in a galaxy that itself is far smaller than ours.
For more details about this weird galaxy, check out the rest of this post at Bad Astronomy. And for more galaxy-black hole weirdness, read last week’s 80beats post about whether mergers of galaxies truly cause supermassive black holes to become hyperactive.
Image: Reines, et al., NRAO/AUI/NSF, NASA