# Regarding the mass of the core of the star

I was reading up about the Chandrashekhar and Oppenheimer Limits when I came across a problem, where the mass of the star could be estimated. My question then is, how can one calculate or estimate the mass of the core of the star. This is important as one can predict how the star evolves and what will be its eventual fate.

• By using the stellar structure equations? – Kyle Kanos Nov 26 '15 at 16:29
• Is there a non-calculus approach where a rough approximation can be used? – model_checker Nov 26 '15 at 16:33
• None that would work reasonably well, as far as I know. – Kyle Kanos Nov 26 '15 at 16:35
• Okay, maybe I'll give you an example(Please share your thought process):If the mass of the star is roughly 14 solar masses, then what kind of star is X? – model_checker Nov 26 '15 at 16:48
• Are stars categorized by their masses or by other things? – Kyle Kanos Nov 26 '15 at 17:01

## 1 Answer

To zeroth-order, the evolution and fate of a star is determined by its Zero-Age Main-Sequence (ZAMS) mass. This determines its core mass. You cannot convert from a total stellar mass to a core mass, because the core mass evolves significantly over time --- as does what the core is over the course of a star's evolution. The most important time is the core-mass at collapse (for massive stars). For high-order accuracy, you need to know any stellar companions (which are likely to exist for high-mass stars), and metallicity/spin/magnetic fields --- but this gets into more uncertain territory...

In general, the basic idea is that stars with ZAMS $M \lesssim 8 M_\odot$ will end their lives as White Dwarfs (WD), with $M \gtrsim 25 M_\odot$ will leave Black-Hole (BH) remnants, and in between will produce Neutron Stars (NS). But these numbers are quite uncertain, and to estimate the fate of a particular system you really need to run a full stellar-evolution calculation.