what's the mass of black holes compared to the galaxy it is located in?

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Offline thebrain13

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I remember reading that it was a cosmic mystery why supermassive blackholes are always approximately 15% of the mass compared to the entire galaxy. However I recently just read that in the milkyway galaxy the ratio of mass in its blackhole is 1/10,000. So what is it? Is the milkyway a statistical oddity or does it refer to only specific types of galaxies? Or is that 15% number just bunk?

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Offline JohnDuffield

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There was a 15% mentioned in the recent story about a gargantuan black hole found in a dwarf galaxy. I've seen various news items about supermassive black holes where cosmologists have tried to establish some kind of ratio, but I don't remember reading anything about supermassive black holes always being circa 15% of the mass of their galaxy.

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Offline PmbPhy

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There was a 15% mentioned in the recent story about a gargantuan black hole found in a dwarf galaxy. I've seen various news items about supermassive black holes where cosmologists have tried to establish some kind of ratio, but I don't remember reading anything about supermassive black holes always being circa 15% of the mass of their galaxy.

thebrain13 - "JohnDuffield" is a major crackpot. Beware!!!

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Offline chiralSPO

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I don't think there could be a fixed constant that relates the mass of a black hole with that of the galaxy it is in. A black hole surrounded by matter is a non-equilibrium environment, and will change as time goes on. Black holes grow and shrink, but mostly they grow, so I would expect that older galaxies would have a larger percentage of their mass in a black hole.