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lmxbftw t1_j5oqq0c wrote

Reply to comment by 9dnguy in How do we know that the biggest known stars are actually so big and not just regular sized ones at the end of their "life"? by realzanji

No, black holes aren't considered stars. Those super massive ones are enormous, though - the radius is linear to mass, and a 1 solar mass black hole has a radius of 3 km. So a 40 billion solar mass black hole would have a radius of about 120 billion km! Which is about 20 times further out than Pluto is, on average.

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Krail t1_j61yhi4 wrote

How does that compare to the further most reaches of the solar system? (Like, to the Heliopause? Is that the considered the edge of the solar system?)

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lmxbftw t1_j623uu9 wrote

It's about 6-7 times further out than the heliopause. (The heliopause is far from spherical, since the Sun is moving relative to the ISM, but from the close part of it.)

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