Robert McNees
Subrahmanyan Chandrasekhar was born #OTD in 1910. He established an upper limit on the mass of stable white dwarf stars, and made numerous contributions to astrophysics and relativity.
Above the Chandrasekhar Limit – about 1.44 solar masses – stars eventually explode and then collapse into a neutron star or black hole.
Photo: Stephen Lewellyn / AIP
Robert McNees
A white dwarf star with mass below the Chandrasekhar limit has settled down into a stable configuration. I guess that's okay if you're into quiet endpoints for stellar evolution. But it's no neutron star or black hole, imo.
Robert McNees
Chandrasekhar presented his results on electron degeneracy pressure and the maximum mass of a stable white dwarf star to a meeting of the Royal Astronomical Society in January of 1935.
The Chandrasekhar Limit of 1.44 M☉ is around 3 x 10³⁰ kg. Above this mass, electron degeneracy pressure can’t prevent further gravitational collapse. The star will eventually become a neutron star or black hole.
Robert McNees
You can see the original summary of Chandrasekhar's presentation in this issue of "The Observatory."
Edward Arthur Milne immediately spoke up after Chandra to say he was working on the same problem and had obtained similar results.
https://ui.adsabs.harvard.edu/abs/1935Obs....58...33./abstract
Robert McNees
That same issue contains the entirety of Arthur Eddington's infamous ambush on his young protege Chandrasekhar, delivered in the next talk.
Robert McNees
Over the following months and then years, Eddington’s attacks on Chandrasekhar’s result became even more heated. He called it “stellar buffoonery” and devised increasingly outlandish reasons why it must be wrong.
Chandrasekhar was hurt by the attacks and felt betrayed by a friend and mentor. But many of Chandra’s contemporaries realized that Eddington — a giant of the field — was *wrong*.
Luminaries like Pauli and Dirac understood Chandra had discovered something new and deep about Nature.
Robert McNees
Definitive proof of Chandra's conjecture came decades later.
Jocelyn Bell made the first pulsar observation in 1967; we now know that these are rapidly rotating neutron stars.
The intense X-ray source Cygnus X-1 was identified in 1972 and eventually confirmed as a black hole.
Nowadays @LIGO routinely detects gravitational waves from pairs of these compact objects spiraling into each other. BH-BH, BH-NS, and NS-NS mergers have all been observed!
Robert McNees
Here's a chart showing the various mergers detected by LIGO-Virgo-KAGRA.
Clicking this link takes you to an interactive version that shows data for each merger:
https://ligo.northwestern.edu/media/mass-plot/index.html
Image: LIGO-Virgo-KAGRA / Aaron Geller / Frank Elavsky (Northwestern)
Covidiocracy
@mcnees He was great in Super Troopers
Robert McNees
@ampersine directed some great episodes of Arrested Development
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