Chandrasekar’s Stand

It was the year 1930. Subrahhmanyan Chandrasekar was on a steamer bound for his new life studying in England.

For Chandrasekar, it should have been a voyage of discovery that he had well earned through hard work. He had attended the finest schools at home and was accepted into Cambridge.

He also learned as much as he could about the new sciences of quantum mechanics and astrophysics. Some of his favorite authors were Arnold Summerfield and R. H. Fowler, who taught there. He also learned about white dwarfs from the book Internal Constitution of the Stars by British astrophysicist Arthur S. Eddington, a man that would soon be his teacher.

Chandrasekhar was looking forward to a long friendship with Eddington and sharing his ideas with this famous man respected throughout Europe.

Chandrasekhar learned that Eddington was fascinated with white dwarfs because of their incredible density. For example the star Sirius B (which orbits the other Sirius every 50 years), has a density of 4 million grams per cubic centimeter. The sun has a density of 1.4 grams per cubic centimeter. A cubic inch of Sirius B would weigh as much as 2 locomotives!

Eddington did not seem troubled by the idea that a star’s core could collapse. But he believed that a white dwarf could always use subatomic repulsion as a backup for internal thermal pressure.

Chandrasekhar disagreed. He was familiar with an article R.H. Fowler wrote in 1926 called On Dense Matter. And he felt the factor of electron degeneracy had to be considered.

When an electron is inside a high pressure environment, such as inside a white dwarf star, it is confined to smaller and smaller regions of space and the lowest levels of energy. In this state, the electron shakes uncontrollably. This is electron degeneracy.

In the extreme temperatures inside white dwarfs, electrons reach speeds well over half the speed of light. So before any light barrier is crossed, the tremendous energies of electrons must be manifested in some other way besides speed – extra mass.

As Lise Meitner showed us, matter and energy are interchangeable. The harder electrons work to resist gravitational collapse, the more they increase in mass and the more gravity they give themselves to work against.

While he was still aboard the ship, Chadrasekhar calculated the equations to show any white dwarf that was heavier than 1.4 suns could not support itself against its own gravity. Therefore no white dwarf could have a mass more than 1.4 solar masses and he had the mathematics to prove it. He could not wait to show his discovery to Dr. Eddington.

When the 2 met Chandrasekhar showed his equations to Eddington and Eddington permitted him to announce his discovery at a meeting.

At first, Chadrasekhar could not see that Eddington had any qualms about him discussing his conclusion. So Chadrasekhar felt free to make one of the boldest statements ever made in astrophysics: the nuclear forces inside of a star, supposedly the strongest force in all the universe, is not enough to resist the crush of gravity inside a white dwarf that has a mass of 1.4 solar masses or more.

When Chadrasekhar finished speaking, Eddington commented briefly, stating that in his view, the idea that a star’s core could implode under its own gravity was absurd. Perhaps it was just an aside but it was a huge blow to Chadrasekhar’s theory.

In those days few scientists were willing to publicly disagree with a scientist as esteemed as Dr. Eddington. It would be a long time before Chadradsekhar would again be taken seriously.

He did get quiet support from a few men like Leon Rosenfield and the Danish physicist Niels Bohr.

On a personal note, when I was writing Chronosia, I was looking for a name of the community of the planet Artemis. I had picked Helmet Hill but after I read the story of Chadrasekhar’s stand, I felt obliged to name the community after him.

We now know that Chadrasekhar was correct and that white dwarfs do implode. But what happens when they do? The march of science continues with a physics teacher from Caltech.