<p>The Sun is said to become a red giant at the end of its life (before that it will become an orange subgiant first and then an orange giant or so) and after ejecting its outer layers it should become a white dwarf. If yellow dwarfs like the Sun become red giants, what do red dwarfs become? Even redder giants? How do the red giants of former red dwarfs (say Proxima Centauri) differ from those of former yellow dwarfs (say the Sun) and how would Proxima's white dwarf be different from the Sun's white dwarf? I mean, a red dwarf's eventual white dwarf would be much less massive than that of the Sun, right?</p>

CC BY-SA 4.0
2020-08-14T07:27:12.447Z
Did you read https://en.m.wikipedia.org/wiki/Stellar_evolution ?
planetmaker
CC BY-SA 4.0
2020-08-14T08:11:40.437Z
"Recent astrophysical models suggest that red dwarfs of 0.1 M☉ may stay on the main sequence for some six to twelve trillion years, gradually increasing in both temperature and luminosity, and take several hundred billion years more to collapse, slowly, into a white dwarf. Such stars will not become red giants as the whole star is a convection zone and it will not develop a degenerate helium core with a shell burning hydrogen. Instead, hydrogen fusion will proceed until almost the whole star is helium." Very interesting. What do such helium stars look like?
Giovanni
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2020-08-15T19:35:43.430Z
[Sitcoms](https://en.wikipedia.org/wiki/Red_Dwarf)
Bob Jarvis - Слава Україні
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2020-08-15T22:11:21.480Z
@Giovanni Those are called "helium white dwarfs". Some are known: although the universe isn't old enough for an isolated red dwarf to have evolved to this stage, they can also be formed if an evolved star in a binary system loses enough mass to its companion.
John Doty
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2020-08-16T05:09:48.503Z
@JohnDoty How do they differ from "default" white dwarfs and how are helium white dwarfs calssified (spectral class)?
Giovanni
CC BY-SA 4.0
2020-08-16T14:52:44.167Z
@Giovanni White dwarfs have their own classification system(s) https://en.wikipedia.org/wiki/White_dwarf#Atmosphere_and_spectra. However, the spectral class doesn't tell you whether the object under the shallow hydrogen/helium photosphere is made of helium or (more commonly) carbon and oxygen. See https://arxiv.org/pdf/astro-ph/0404291.pdf for an example of the more intricate work needed to distinguish.
John Doty
<stellar-evolution><white-dwarf><red-giant><red-dwarf>
If Sunlike stars become a red giant and eventually a white dwarf, what do red dwarfs become?
Giovanni
# If Sunlike stars become a red giant and eventually a white dwarf, what do red dwarfs become?

(Asked by: username_0 on 2020-08-14)

The Sun is said to become a red giant at the end of its life (before that it will become an orange subgiant first and then an orange giant or so) and after ejecting its outer layers it should become a white dwarf. If yellow dwarfs like the Sun become red giants, what do red dwarfs become? Even redder giants? How do the red giants of former red dwarfs (say Proxima Centauri) differ from those of former yellow dwarfs (say the Sun) and how would Proxima's white dwarf be different from the Sun's white dwarf? I mean, a red dwarf's eventual white dwarf would be much less massive than that of the Sun, right?

**Tags:** stellar-evolution, white-dwarf, red-giant, red-dwarf
> **Comments:**
> **username_1**: Did you read https://en.m.wikipedia.org/wiki/Stellar_evolution ?  
> **username_0**: "Recent astrophysical models suggest that red dwarfs of 0.1 M☉ may stay on the main sequence for some six to twelve trillion years, gradually increasing in both temperature and luminosity, and take several hundred billion years more to collapse, slowly, into a white dwarf. Such stars will not become red giants as the whole star is a convection zone and it will not develop a degenerate helium core with a shell burning hydrogen. Instead, hydrogen fusion will proceed until almost the whole star is helium." Very interesting. What do such helium stars look like?  
> **username_2**: [Sitcoms](https://en.wikipedia.org/wiki/Red_Dwarf)  
> **username_3**: @Giovanni Those are called "helium white dwarfs". Some are known: although the universe isn't old enough for an isolated red dwarf to have evolved to this stage, they can also be formed if an evolved star in a binary system loses enough mass to its companion.  
> **username_0**: @JohnDoty How do they differ from "default" white dwarfs and how are helium white dwarfs calssified (spectral class)?  
> **username_3**: @Giovanni White dwarfs have their own classification system(s) https://en.wikipedia.org/wiki/White_dwarf#Atmosphere_and_spectra. However, the spectral class doesn't tell you whether the object under the shallow hydrogen/helium photosphere is made of helium or (more commonly) carbon and oxygen. See https://arxiv.org/pdf/astro-ph/0404291.pdf for an example of the more intricate work needed to distinguish.  

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## 0 answers

