[elorant]

The Great Filter can be a myriad of things. From how improbable life is to the hostility of the Universe. A magnetar has a hiccup and it sterilizes everything in a fifty light year radius. There are a shit ton of things out there that could eradicate life.

[danlugo92]

Wikipedia says closest magnetar is 50k light years from earth...

[elorant]

And the closest Neutron star is 200 ly away moving our way, thankfully in a safe distance in some 300.000 years. Had this thing flung in a short distance it could disturb planetary trajectories.

Supernovas can have the same effect as magnetars, as also black holes. There could even be a tiny one lurking in the outskirts of our solar system (the so-called planet 9). What I wanted to point out is that the Universe is a very hostile place. There could have been myriads of civilization that were eradicated because of a cosmic event every now and then.

[est31]

How is a black hole of the mass of a planet more dangerous than a planet of the mass of a planet?

[elorant]

A black hole can emit gamma rays.

[jjcon]

Black holes do not emit gamma rays... black holes emit nothing (aside from potentially hawking radiation). Matter around supermassive black holes can give off gamma rays but planet massed black holes are just as likely to cause gamma as planets themselves are.

[arrow7000]

Regular planets don't have the incredible concentration of gravitational pull that an event horizon does, so no, planet mass black holes are not only as dangerous as planets are.