The sun itself may get ejected into intergalactic space when the Milky Way merges with Andromeda. (< 5 billion years from now)
Earth will probably be totally engulfed by the sun when it goes red giant, or it might not in which case presumably it will continue orbiting. (7.59 billion years from now)
By 100 billion–1 trillion years from now all galaxies in the local group are expected to have merged, so there will probably be other opportunities for the sun to get yeeted into intergalactic space.
By 10–100 quintillion it's expected that 90-99% of all stellar remnants will be ejected.
Finally, at 10^30 (1 nonillion) years from now, we get this gem:
Estimated time until most or all of the remaining 1–10% of stellar remnants not ejected from galaxies fall into their galaxies' central supermassive black holes. By this point, with binary stars having fallen into each other, and planets into their stars, via emission of gravitational radiation, only solitary objects (stellar remnants, brown dwarfs, ejected planetary-mass objects, black holes) will remain in the universe.
One thing to keep in mind though is that by the time our sun gets sucked into a black hole, the galaxy will have merged so it may very well be a different black hole, or this paticular black hole may have merged with multiple other ones.
On the timescale from now until the sun goes nova, confident "no".
Roughly speaking, the sun orbits the galactic center at a velocity of 220km/s. To fall into, or to be sucked into, the central black hole would require the loss of all this velocity, which means applying acceleration to the sun opposite the direction of its orbit. Lots of acceleration. That has to come from somewhere.
I suppose there's some extremely tiny amount of drag that occurs due to the sun moving in the interstellar medium, but aside from that there's not a lot that applies acceleration to the sun opposite the direction of its orbit. Really the only other thing that comes to mind are the gravitational waves that are radiated by co-rotating objects. This is the effect that causes close by black holes to eventually come close enough that they merge. But in objects traveling at slower speeds in larger orbits, this effect is also negligible on the scale of billions of years. (These are the gravitational waves observed by LIGO). https://en.wikipedia.org/wiki/Two-body_problem_in_general_re...
This has been bugging me. I was absolutely confident a (non-super) nova was an expected event in the evolution of sun-mass stars. Currently, though, the scientific term "nova" (excluding supernovae) clearly is applied only to a situation with binary stars, where a white dwarf siphons off matter from a less dense but heavier companion star. There are other specific things that happen to solar-mass red giant stars, such as helium shell flash, a rapid but short-lived change in brightness that can also leave a planetary nebula. Such an event could sound like it meets the definition of a "nova" but it doesn't meet today's technical definition of it.
It seems like the assignment of "nova" to a common stage of solitary low-mass stellar development is outmoded, so a change in nomenclature could help explain my confusion. For instance, this 1986 book https://archive.org/details/privatelivesofst00gall/page/68/m... states "Stars called novae explode and grow much brighter over a period of days or weeks, then return to normal again, usually over several years. Although we have ideas about nova stars, we have a lot more to learn about them. [...] When a red giant collapses and is well on its way to white dwarfhood, it may go through one or more periods of being unstable. At such times the star may erupt as a nova. This may be especially so of the more massive stars."
If the Sun were replaced by black hole with the same mass as the Sun at the center of the Solar System we wouldn't automatically get sucked into it. A very cold Earth would continue to orbit the black hole exactly as it does the Sun today. Only if the Earth's orbit were perturbed by some other body would it have a chance of joining the black hole.
> Only if the Earth's orbit were perturbed by some other body would it have a chance of joining the black hole.
Not any more meaningfully than the chance of current-Earth being put on a trajectory to crash into the sun if its orbit were perturbed. A black hole doesn't magically have a stronger (instantaneous) gravitational pull than that of any other body; the same formula for gravitational force at distance D given object masses Mi is preserved. Now the typical means of formation for a black hole generally result in masses much greater than that of our sun, which is why they are generally heavier and, accordingly, stronger (and they gain mass as they suck up things around them, hence the "instantaneous" disclaimer above).
