# How can a low-mass star increase its mass to 1.4 Msun? [closed]

In my astronomy class I learned that a only low-mass stars (< 0.5 Msun) will contract, and then become degenerate, until it is a white dwarf. However, we also learned about the Chandrasekhar limit, which states white dwarfs have a maximum mass of 1.4 Msun.

If the starting star has less than 0.5 Msun, how does the resulting white-dwarf reach up to 1.4 Msun?

Am I perhaps wrong in my assumption that the mass of the resulting white-dwarf depends on the mass of the original star?

## closed as off-topic by Donald.McLean♦Mar 14 '16 at 13:23

• This question does not appear to be about astronomy, within the scope defined in the help center.
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• Nb You have put an identical question on Physics SE, which I have answered. This question should be closed. – Rob Jeffries Mar 14 '16 at 7:11
• See identical duplicate physics.stackexchange.com/questions/243298/… – Rob Jeffries Mar 14 '16 at 7:14
• This question has been posted on multiple sites. Cross-posting is strongly discouraged; see the help center and community FAQ for more information. – Donald.McLean Mar 14 '16 at 13:23
• I don't think this question should be closed. Ignoring the cross-posting, this question is definitely about astronomy and is not off-topic. I would say better suited to here than Physics SE! – FJC Mar 14 '16 at 13:42
• @FJC For questions that are on-topic on two sites, the user gets to pick. By accepting the answer on Physics, they have de-facto picked that site. – Donald.McLean Mar 14 '16 at 13:52

There is a non-linear, but probably monotonic, relation between the initial progenitor and final white dwarf masses (see below, from Kalirai 2013) - the Sun will likely end as a 0.5 solar mass white dwarf, but in normal stellar evolution, degenerate white dwarf stars can only be produced up to about 1.25 solar masses by the most massive progenitors. Any more massive than this and it is likely that the core does not become degenerate before igniting and burning through the heavier nuclear fuels. The most massive, probably single, white dwarf known is "WD 33" in the cluster NGC 2099 and has a mass of $1.28^{+0.05}_{-0.08}\ M_{\odot}$, is likely made of an O/Ne mixture, and had an estimated progenitor mass on the main sequence of $>3.5\ M_{\odot}$ (Cummings et al. (2016).