Potential Supernovae (Earth, stars, Sun, Milky Way)

[Milky Way Resident]

Are the Sirius double system and the Alpha Centauri triple one likely to produce at least a Type I supernova?

Sirius already has a white dwarf, whereas the Alpha binaries are of similar mass to the sun. What would happen to Proxima Centauri then? Red dwarfs are expected to last for trillions of years, but could a supernova in the Alpha Centauri system destroy Proxima?

[rjshae]

Unlikely. The typical scenario for a Type 1a supernova is that the white dwarf is orbiting close enough to a red giant companion to accrete matter up until it reaches the Chandrasekhar mass: 1.4 times the mass of the Sun. The white dwarf in the Sirius system is probably orbiting too far out for this to happen. Likewise, when the inner pair of the Alpha Centauri system end up as white dwarfs, they will have ejected a significant portion of their masses so there may not be enough left to reach the necessary limit. Plus they are currently orbiting too far apart to undergo accretion. If they did somehow undergo a supernova (such as via a white dwarf merger), Proxima Centauri is orbiting quite a distance away so possibly it may survive, albeit with a lower mass.

For a nearby example of a system that may become a Type 1a supernova, see IK Pegasi.

https://en.wikipedia.org/wiki/IK_Pegasi

[2x3x29x41]

Originally Posted by Milky Way Resident

Are the Sirius double system and the Alpha Centauri triple one likely to produce at least a Type I supernova?

Sirius already has a white dwarf, whereas the Alpha binaries are of similar mass to the sun. What would happen to Proxima Centauri then? Red dwarfs are expected to last for trillions of years, but could a supernova in the Alpha Centauri system destroy Proxima?

No.

First, it is very unlikely for the Alpha Centauri system to produce a supernova. None of the three stars is big enough to undergo a Type II supernova. Alpha Centauri A, being larger than Alpha Centauri B, will progress to white dwarf-dom first. A Type Ia supernova would then be theoretically possible, but A & B are currently far too distant for matter accretion to occur. A gravitational perturbation (from a passing system) would be required to nudge the two closer together. Possible - but very unlikely.

Second, Proxima Centauri (or, Alpha Centauri C) would not be harmed beyond perhaps losing a little stellar atmosphere. A supernova isn't a blast in the conventional sense that we understand one on Earth. Really, the term 'explosion' is what misleads us; it is an explosion, but not as we conventional understand one to be. C would be bombarded by neutrinos and electromagnetic radiation, but it wouldn't be impacted per se in any real physical way beyond its orbit increasing somewhat due to mass-loss by A going supernova.

Note:
Long before even the remote possibility of a supernova in the Alpha Centauri system could be realized, two things will have occurred: 1) the Sun will have long since rendered the Earth uninhabitable (this is expected to occur in less than a billion years, due to the gradual increase of the Sun's luminosity), and 2) Alpha Centauri will be somewhere else (compared to the Sun and the Earth) in the Milky Way, due to the galaxy's differential rotation.

[Diesel23]

Sirius B, a white dwarf orbits too far to accrete matter from Sirius. The red dwarf, Alpha Proxima, is orbiting too far from the G and K type stars at the center of the Alpha Centari system, and they in turn orbit too far from each other to accrete matter from each other. Being a red dwarf, Alpha Proxima will likely burn for another trillion years or so before running out hydrogen nuclear fuel being fused for fuel.