What is the mass of the supermassive black hole in the centre of the universe and how would you calculate that?

Best answer: You appear to be calculating the mass of all the stars and other stuff inside the orbit of the solar system around the Milky Way. The central black hole is a very small part of that total mass. The mass of Milky Way is about 1000 BILLION solar masses, and we are about 2/3 of the way out from the center.

In order to figure the mass of the central black hole, you need to consider something that orbits close to that BH. That is what various astronomers have done, looking at the orbit of the star "S2". Even then, they figure that there are thousands of other stars close to S2's orbit. But all that stuff is less than 1% of the BH.

5 Answer(s)

Your mistake is that you're assuming the central black hole is most of the mass of the galaxy. That's not the case; most of the galaxy's mass is stars, nebulae, and dark matter, and only a small percentage is in the central black hole. The Sun's orbit is basically down to the combined gravity of all those things.

Center of the galaxy, not the universe

Not universe in any case - black hole is center of galaxy, which is a tiny part of the universe

You appear to be calculating the mass of all the stars and other stuff inside the orbit of the solar system around the Milky Way. The central black hole is a very small part of that total mass. The mass of Milky Way is about 1000 BILLION solar masses, and we are about 2/3 of the way out from the center.

In order to figure the mass of the central black hole, you need to consider something that orbits close to that BH. That is what various astronomers have done, looking at the orbit of the star "S2". Even then, they figure that there are thousands of other stars close to S2's orbit. But all that stuff is less than 1% of the BH.

You have essentially derived your formula from KLT (Newtonian version):
(P/2π)² = a³/GM .
You have taken P ('t' for you) as 226 million years, that is at the Sun's distance (at 54% Galactic disc radius). The P is variable with its distance from the centre.