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I have seen in internet and books that the largest practical unit for mass is Chandrasekhar limit which is 1.4 times the mass of sun. It gives the minimum mass for a star to become a neutron star. But there is a bigger unit called TOV limit which gives the minimum mass required for a star to become a black hole which is 3 times the mass of sun.

Are these units the largest natural units of mass?

Would these units of mass be more useful than the solar mass?

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    $\begingroup$ You could argue the largest practical unit of mass is one kilo, a nice human scale for mass. But you could construct arguments for any mass being the largest practical unit. If I'm discussing galaxies, the mass of the Milky Way seems a good choice. But why not the mass of the local group or something else ? Seems like a matter of opinion and context. $\endgroup$
    – StephenG - Help Ukraine
    Apr 28, 2018 at 14:43
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    $\begingroup$ Re close button. Ok this is a poorer quality question written by somebody with a non-expert knowledge and not perfect English. But it is obviously meant as a genuine enquiry. Can we fix it rather than auto close vote ? $\endgroup$
    – Martin Beckett
    Apr 28, 2018 at 14:49
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    $\begingroup$ The Chandrasekhar limit cannot be used as a unit because it is not a constant, it is itself a function of a star mass. $\endgroup$
    – Stéphane Rollandin
    Apr 29, 2018 at 16:34

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Because units of mass (like units of anything) are used to quantify other things, eg. the star Betelgeuse has a mass about 10x that of the sun - a solar mass is a useful sized unit rather than writing a very long answer in Kg. Using the Chandrasekhar limit doesn't really gain anything in understanding.

Possibly they are more universal in that they are the same everywhere, while solar mass is a local unit. If we ever need to read astrophysical papers from an alien civilisation this might become a minor issue (like reading USA weather reports).

You could argue that using the minimum theoretical mass for a star would be more useful to compare different stars - since no answer would be a fraction. But mainly we would have to re-learn the axis on all those diagrams.

In larger scale cosmology the mass of a galaxy might be a more useful unit

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  • $\begingroup$ Probably would be possible to scale the stellar mass unit to the mean mass of the IMF, but then it'd depend on which IMF one chooses... $\endgroup$
    – Kyle Kanos
    Apr 28, 2018 at 19:28

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