How does a heavy star end?

That time, that place

A star pulls itself in by gravity while the heat of fusion pushes out. The balance between them is the star's life.

When the fuel runs out the push stops. What then? The answer at the time was a white dwarf: shrink to something small and dense and cool slowly.

Why this question

Chandrasekhar was nineteen. He did the calculation on the ship from India to Cambridge.

What stops the collapse is Pauli's exclusion principle: electrons cannot share a state, so compression halts.

But in a very heavy star the electrons move near light speed. Relativity must go in, and once it does the resistance is weaker than expected.

The limit came out at about 1.4 solar masses. Above that, a star cannot stop as a white dwarf.

What was found

When he presented it to the Royal Astronomical Society in 1935, Eddington — the leading authority of the day — rose immediately to dismiss it, on the grounds that nature could not permit so absurd an ending.

The room sided with Eddington. Chandrasekhar dropped the subject and moved to other fields. He was Indian and twenty-four.

What lies beyond that limit is the neutron star and the black hole. He received the Nobel Prize in 1983, forty-eight years after the talk.