It’d be pretty close to breaking apart. The Roche limit (the point at which gravitational binding force of the planet is equal to the tidal force) for the earth orbiting a 4-million M[sub]sol[/sub] black hole is about 0.6 AU. (That’s a first order estimate but I think it’s in the right order of magnitude.)
Any guesses on how large and dense the accretion disk would be? I have a feeling that’d be a major obstacle.
OK, I was working under the assumption that getting light from t herest of the sky could well be problematic. However, seeing as the density of stars in the disk is greater than out here, I can see this won’t be a problem.
I don’t think the accretion disc is would be too major as Sag. A* is not an active galactioc nuclei which means that there is no large, constant infall of matter otherwise it would be an active galactic nuclei (quasar/blazar/radio galaxy).
Indeed, the accretion disc shouldn’t be too much of a problem. However, since we’re in a spiral galaxy, if the nucleus was active, we’d probably be more of a Seyfert galaxy rather than quasar/blazar/radio galaxy, which tend to be hosted by giant ellipticals.
S2 orbits the central hole with a period of 15.2 years and a semi-major axis of 5.5 light days. Applying simple centrifugal calculations (rcf = 0.00001118 r X RPM^2) gives a value of ~0.0012 g. That’s using the semi-major axis in a circular orbit. The value would be higher for an ellipse.
I’d expect that 0.0012 g acting on the outer atmosphere of a star would cause some major hydrogen leakage, or am I all washed up here ?
FYI, he later expanded it into a full novel, which of course gave a lot more background and fleshed out the story (and the aftermath) quite a bit. In that, it was 2,000 years, but I don’t remember if it was different in the original short story. Worth reading, I think.
Though what little I’ve read about orbital mechanics would seem to indicate that the scenario would be wildly improbable - although in an infinite universe, it’s gotta happen somewhere, right?
Yeah, I wasn’t clear in my post. That’s indeed what I meant. You can get closer to the center of a small black hole than a bigger one, so the tidal force can be bigger for a small black hole. A star would get ripped apart by a stellar mass BH, but not necessarily a supermassive one. A star might fall in whole! I don’t have the wherewithal to calculate the Roche limit for a star. Anyone wanna do the full-up polytropic analysis? 
I could be wrong, but in “Nightfall” they were in a cluster, not the galactic core, and there were about 30,000 stars visible to the naked eye, as opposed to the 6,000 we have at Earth.
One thing that bugged me was when they had to pick an order of magnitude for the separation between stars, they picked four light years, which is the typical separation in the solar neighborhood. I mean, come on. Not only would this value be too big for a cluster, but why would they even think it’s so vast if they had never even seen a star?
OK, not the full thing, but my trusty “Cambridge Handbook of Physics Formulas”, aka, my primary bible, gives the Roche limit for a star as
R>~(100M/9pi rho)sup[/sup]
So, if we assume M~4 MM[sub]sun[/sub], and rho=rho_sun~470kg/m[sup]3[/sup]
Then, the Roche limit for a star is
R~2.6AU (or 3.9x10[sup]11[/sup]m)
Comparing this to the Schwartzschild radius (incorrect I know!) of a 4 MM[sub]sun[/sub] black hole, which is 0.08AU, I would think that a star would be ripped apart even by a SMBH. I could be wrong though.