It is believed that there is a black hole at the centre of the Milky Way galaxy. And the sun revolves around the centre of the milky way. So does it mean our sun is revolving around the centre of the galaxy due to this black hole?
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$\begingroup$ Welcome to stackexchange! Take the tour! Both are pretty good questions, but it would be better for you and for the person(s) answering if you ask them separately. The first question is really about what does the term "revolve around" implies, and that may have an answer or three here already. The question about planets around stars near the center of the galaxy is much more interesting. It may also have an answer, but it may not. Split them up for best results, and have fun! $\endgroup$– uhohCommented Apr 3, 2017 at 6:00
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$\begingroup$ Look at these related questions: astronomy.stackexchange.com/questions/7861/… and astronomy.stackexchange.com/questions/16204/… $\endgroup$– James KCommented Apr 3, 2017 at 7:50
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2 Answers
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The Sun orbits in the entire Galactic gravitational potential, which is very approximately similar to that provided by considering that all the mass interior to its Galactic orbit (about 100 billion solar masses) were concentrated at the Galactic centre.
The black hole at the centre has a mass of 4 million Suns, so contributes less than 0.01% of the mass required to keep the Sun in its present Galactic orbit of about 200 million years. Or to put it another way, if the Sun just orbited the black hole with a period of 200 million years, we would need to be about 800 light years from the Galactic centre, rather than the 30,000 light years we presently are.
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$\begingroup$ Can you please explain to me how this massive Galactic gravitational potential is created? $\endgroup$ Commented Apr 3, 2017 at 16:49
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1$\begingroup$ Just to add: It has been shown that only in the very centre do the stars revolve around the super-massive black hole (the S-stars). In fact, as soon as you get to around roughly 1 pc (or 3.26 light years) from the black hole it is the mass distribution of stars that dominate and not the black hole. References: Schneider, P. (2006). Extragalactic Astronomy and Cosmology. Springer. Perets, H. B. (2008). Dynamical and evolutionary constraints on the nature and origin of the hypervelocity stars. Gillessen et all (2009). The orbit of the star s2 around sgr a* from vlt and keck data. $\endgroup$ Commented Apr 4, 2017 at 9:27
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Yes, of course. In the same way as the answer to If the Moon revolves around Earth, does it mean it revolves around you? is Yes!
This does not mean, though, that you determine or even significantly affect the orbit of the Moon, and so it is with the supermassive black hole (SMBH) at the center of the Milky Way and the orbit of the Sun, as Rob explains (but fails to answer your question ;-).
The gravitational tug of the Milky Way at the Sun is the sum of the tugs of all its components, not just the SMBH. This is dominated by the vast number of stars (and dark matter), which together weight much more than the SMBH.
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$\begingroup$ Well thanks! This question popped up my mind because because of the epic proportion of gravitational influence the black hole has on other objects. So I thought maybe the whole galaxy might be revolving around the black hole because of this. But now it's clear. $\endgroup$ Commented Apr 3, 2017 at 16:55