Looking Up: South Side Of The Sky

May 20, 2019

Artist impression of a white dwarf star in orbit with pulsar PSR J2222-0137.
Credit B. Saxton (NRAO/AUI/NSF) / earthsky.org

This week on Looking Up we're bound for a star that's 50 light years from home.

Deep in our southern skies, in the constellation Centarus lies a dead star 50 light-years away from the Earth. V886 Centauri is at first glance an ordinary white dwarf. But it is more than it appears.

A white dwarf is the hot core left behind when a star uses up its nuclear fuel and, in essence, dies. What remains is mostly carbon and oxygen surrounded by a thin layer of hydrogen and helium gases. In 1992, it was discovered that V886 pulsates because its core temperature dropped below 12,000 degrees Fahrenheit. Astronomers decided to do an experiment to see what it was made of by using its pulsation to see if it cooled enough to crystallize.

The process is called “Asteroseismology” which uses the dead star’s spectra to determine its composition the same way that geologists study the interior of the Earth during earthquakes.  Astronomers found that approximately 90% of V886’s mass had crystallized, and since V886’s interior core is mostly made of carbon, it can only mean one thing….it is the biggest diamond ever found!

At 10 billion trillion trillion carats, this stellar diamond is forever.  And, of course, astronomers nicknamed it “Lucy.” So, what I’m literally saying is Lucy’s in the Sky with Diamonds.

If you’d like to take a closer look at a White Dwarf Star, or any of the other wonderful and amazing things in the sky, please visit csastro.org for a link to information on our monthly meetings and our free public star parties!