How would the Sun evolve if it collided with another G-type main sequence star, perhaps a more massive one like Alpha Cen A? Since its mass would then be above the Chandrasekhar limit, could it eventually become a neutron star instead of a white dwarf? Or would it lose enough mass until then so that it would still become a white dwarf, just like Sirius A (whose mass is above the Chandrasekhar limit too but will develop into a white dwarf anyway due to mass loss)? Would the Sun's yellow-dwarf-to-red-giant phase be prolonged due to the additional mass? When largest, would the red giant be bigger than the currently estimated 256 solar radii?

  • $\begingroup$ 2 solar masses is far too light for a star to explode in a core collapse supernova. IIRC, the progenitor of a neutron star needs over 10 $M_\odot$. $\endgroup$
    – PM 2Ring
    Nov 27, 2020 at 12:33
  • 1
    $\begingroup$ Accretion induced collapse (AIC) , is a means of forming neutron stars. $\endgroup$
    – ProfRob
    Nov 27, 2020 at 18:03
  • $\begingroup$ It's a pity PM2Ring deleted his informative comments following his first one and my question in retard. $\endgroup$
    – Greenhorn
    Nov 28, 2020 at 15:23

1 Answer 1


If the Sun collided with another star about the same mass, then its mass would be slightly less than 2 solar masses, as some material would be ejected away from the merger. This would result in an A-type star, as the merger's mass is about 2 solar masses. A good example of a 2 solar mass star is Fomalhaut A, which is an A3V star. Therefore, this merger would be somewhere around Fomalhaut's position on the HR diagram.

If the mass of a star is doubled, then its lifespan is decreased by eightfold, meaning that the merger would live for about $\dfrac{10}{8}= 1.25 \text{ billion years}.$ With that said, the transition to the red giant phase would not be prolonged, but shortened.

When this merger becomes a red giant, its core will have less mass than the Chandrasekhar limit, and become a white dwarf. At its largest, it will exceed 256 solar radii, up to about 400 radii, according to Wikipedia. χ Cygni is a red giant that is about 2 solar masses, which is a good reference to the aging merger. This star will become a white dwarf, so that is further proof that the Sun-merger will have a shorter lifespan as well as not have enough mass to exceed the Chandrasekhar limit.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .