We have known since the 1990s that planets exist around pulsars, which are extraordinarily dense objects born out of the violent explosions of stars. It is therefore reasonable to assume that planets might also exist around black holes, which, perhaps surprisingly to many people, have a much weaker impact on their environment than pulsars. It’s even possible that life may form on some of these planets, given that organisms on Earth have adapted to extreme conditions, including boiling heat, freezing cold, and acidic, highly salty and even radioactive environments.
Inhabited planets could exist near the supermassive black holes that lie at the cores of most galaxies. Our own galaxy, the Milky Way, harbors a black hole whose mass is as great as four million stars put together. Known as Sgr A* (Sgr stands for Sagittarius), its innermost stable circular orbit (ISCO) has roughly the size of the orbit of Mercury around our sun.
So, what would life be like on such a planet?
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