<p>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 <a href="https://en.wikipedia.org/wiki/Fomalhaut" rel="noreferrer">Fomalhaut A</a>, which is an A3V  star. Therefore, this merger would be somewhere around Fomalhaut's position on the HR diagram.</p>
<p>If the mass of a star is doubled, then its lifespan is decreased by eightfold, meaning that the merger would live for about <span class="math-container">$\dfrac{10}{8}= 1.25 \text{ billion years}.$</span> With that said, the transition to the red giant phase would <strong>not be prolonged, but shortened.</strong></p>
<p>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 <a href="https://en.wikipedia.org/wiki/Chi_Cygni" rel="noreferrer">Wikipedia</a>. 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 <strong>the Sun-merger will have a shorter lifespan as well as not have enough mass to exceed the Chandrasekhar limit.</strong></p>

CC BY-SA 4.0
2020-11-27T14:13:18.457Z
2020-11-27T14:13:18.457Z
WarpPrime
<p>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?</p>

CC BY-SA 4.0
2020-11-27T12:33:02.177Z
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 $M_\odot$.
PM 2Ring
CC BY-SA 4.0
2020-11-27T18:03:39.597Z
Accretion induced collapse (AIC) , is a means of forming neutron stars.
ProfRob
CC BY-SA 4.0
2020-11-28T15:23:39.650Z
It's a pity PM2Ring deleted his informative comments following his first one and my question in retard.
Greenhorn
<star><the-sun><stellar-evolution><main-sequence><collision>
What would happen to the Sun's evolution if it collided with another yellow dwarf?
Greenhorn
# What would happen to the Sun's evolution if it collided with another yellow dwarf?

(Asked by: username_0 on 2020-11-27)

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?

**Tags:** star, the-sun, stellar-evolution, main-sequence, collision
> **Comments:**
> **username_1**: 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 $M_\odot$.  
> **username_2**: Accretion induced collapse (AIC) , is a means of forming neutron stars.  
> **username_0**: It's a pity PM2Ring deleted his informative comments following his first one and my question in retard.  

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## 1 answers

### Answer by username_3 on 2020-11-27. Score: 5 | Accepted answer

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](https://en.wikipedia.org/wiki/Fomalhaut), 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](https://en.wikipedia.org/wiki/Chi_Cygni). 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.**


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