The Chandrasekhar limit is approximately how many solar masses?

• A. 0.8 solar masses
• B. 1.44 solar masses
• C. 2.0 solar masses
• D. 3.0 solar masses

Answer: (B)

The idea being tested is the maximum mass a white dwarf can support with electron degeneracy pressure before gravity overcomes that pressure. As a white dwarf gains mass, gravity squeezes it harder and the electrons are pressed to higher speeds. When the electrons become relativistic, the degeneracy pressure no longer increases quickly enough to support more mass, so there is an upper limit.

For typical carbon-oxygen white dwarfs, the mean molecular weight per electron is about 2, and the balance of fundamental constants gives a Chandrasekhar limit of roughly 1.44 solar masses. If a white dwarf approaches this mass, it can no longer remain stable and will collapse into a neutron star or trigger a Type Ia supernova.

The other numbers don’t fit because 0.8 solar masses is well below the limit a degenerate white dwarf can support, while 2.0 and 3.0 solar masses exceed the stability bound for a white dwarf and would lead to collapse or explosion rather than a stable white dwarf.