How a white dwarf forms may be of interest to us as the Sun will turn into one of these bizarre objects in another 5 billion years. But first of all, what is a white dwarf again?
The story begins only long after the Sun uses up all of its available hydrogen and helium fuel. At this point the core of the Sun’s long-lived (10 billion year old) former nuclear fusion reactor will be exposed as a white-hot “coal” or possibly even a “diamond.” Its initial temperature will be high, 10,000 degrees Kelvin, Celsius, or Fahrenheit (at these temperatures, take your pick).
Over time white dwarfs will cool and shrink ever so slowly similar to that of a lonely yule log. White dwarfs are quite bright as a result of being so hot, such that astronomers can readily find them. And some white dwarfs are at different temperatures, indicating that they formed over a range of ages. What astronomers have not found are any white dwarfs that are actually shrinking, that is until now.
In a recent study reported in Astronomy magazine on November 16th led by Sergei Popov, a white dwarf was found which is spinning fast. This is not so unusual, as white dwarfs which are all roughly Earth-sized can spin at a rate of once every 13 seconds (compared to 24 hours for the Earth). What is surprising is that the rate of spin is increasing at such a clip that it can only be explained if the white dwarf is also getting smaller. This is similar to saying that
based only on the fact that a figure skater is starting to spin very fast you intuit that this athlete must have started out spinning with arms extended and is now pulling them inward close to the body, effectively also getting “smaller.”
This discovery is helping astronomers to understand what happens when matter that is compressed to these ultra-high densities behaves and evolves over time. This is important as such matter cannot be made in the laboratory on Earth.
By the way, one amazing fact to tell at the Thanksgiving dinner table is that one teaspoonful of a white dwarf weighs as much as an elephant.