White dwarfs

1931 White dwarfs

The book of science

Tom Sharp

Subrahmanyan Chandrasekhar astronomy White dwarfs

White dwarfs

Unlike main sequence stars, white dwarfs resist gravitational collapse due to electron degeneracy pressure but collapse if they have greater than about 1.44 solar masses, a number known as the Chandrasekhar limit, and then they explode as supernovas and collapse into neutron stars or black holes. At the age of 19, Subrahmanyan Chandrasekhar predicted this even when the scientific community had not accepted the possibility of black holes.

Solidity

The solidity of ordinary matter is an effect of the refusal of fermions, including electrons, to occupy the quantum state of another fermion. This is called quantum degeneracy pressure. A white dwarf has depleted all or most of its fusionable matter, so it is not supported against collapse by the heat of fusion reactions. Its extremely dense core of carbon and oxygen, provided that it stays under the Chandrasekhar limit and is not rotating extremely fast, resists collapse only by electron degeneracy pressure.

Pressure

If my work were indistinguishable from another poet, always writing the same things and publishing in the same places, you could make a case that I and the other were two names for one person. I would be outraged to discover someone else signing my checks, but the proposition that we have no need for duplicate identities is invalidated by numerous Elvis impersonators and karaoke artists singing “I did it my way.” In some cultures and companies, conformity is valued. Mass media mocks itself but many people take it seriously and assume the dress, speech, habit, even personality of a character acted out to keep you watching the show until the next commercial gets you to buy the same mass-produced shoes, beers, cereals, or fast-food brands. It’s depressing. Often it’s only when a person discovers his or her own identity or comes out that he or she can resist the evil of peer pressure. It is helpful to realize that peer pressure is not the only kind of pressure that a caring and intelligent individual must resist. Imitation is a form of flattery, but we already have an excellent William Carlos Williams and a wonderful William Blake. Eventually we might suffer the same death but, while we’re alive, our individual variations are more than interesting.

Although white dwarfs are not “main sequence” stars, not included in the theory of stellar evolution described by Arthur Eddington and others in 1920, they are thought to be the final evolutionary state of over 97% of stars in our galaxy.

See also in The book of science:

Readings in wikipedia: