[jepler]

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...

[perardi]

[pushes up glasses]

The Sun is nowhere near massive enough to become supernova.

https://en.wikipedia.org/wiki/Sun#After_core_hydrogen_exhaus...

It will become a red giant, and then eventually end up a white dwarf.

[jepler]

Thanks for the correction. You're right, current scientific thinking is that the sun is not capable of going "supernova".

[jepler]

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."