Earth and Space

Surprisingly dense stars

Stories from Physics for 11-14 14-16 IOP RESOURCES

The high density of white dwarf stars was a surprise to astronomers. The Estonian astronomer Ernst Öpik (grandfather of the former British Liberal Democrat MP Lembit Öpik) calculated the density of Sirius B - now known to be a white dwarf - and declared the answer “impossible”. Öpik is also to be credited for postulating the idea of the Oort cloud, a shell of icy objects beyond the edges of the solar system, before it was suggested by Oort.

Eddington expressed his shock at the density of white dwarfs in a lecture:

We learn about the stars by receiving and interpreting the messages which their light brings to us. The message of the companion of Sirius when it was decoded ran: “I am composed of material three thousand times denser than anything you have ever come across; a ton of my material would be a little nugget that you could put in a match-box.” What reply can one make to such a message? The reply which most of us made in 1914 was: - “Shut up. Don’t talk nonsense.”


Limit Less Campaign

Support our manifesto for change

The IOP wants to support young people to fulfil their potential by doing physics. Please sign the manifesto today so that we can show our politicians there is widespread support for improving equity and inclusion across the education sector.

Sign today