White Dwarf Star

To us, stars may resemble cut jewels, glittering coldly against the velvet darkness of the night sky. And for some of them, that may actually be sort of true.

As a certain type of dead star cools, it gradually hardens and crystallizes. Astronomers have found one doing just that in our cosmic backyard, a white dwarf composed primarily of carbon and metallic oxygen just 104 light-years away, whose temperature-mass profile suggests that the center of the star is transforming into a dense, hard, 'cosmic diamond' made up of crystallized carbon and oxygen.

The discovery is detailed in a paper accepted into the Monthly Notices of the Royal Astronomical Society and available on preprint website arXiv.

"In this work we present the discovery of a new Sirius-like quadruple system at 32 parsecs distance, composed of a crystallizing white dwarf companion to the previously known triple HD 190412," write an international team of astronomers led by Alexander Venner of the University of Southern Queensland in Australia.

"By virtue of its association with these main sequence companions, this is the first crystallizing white dwarf whose total age can be externally constrained, a fact that we make use of by attempting to empirically measure a cooling delay caused by core crystallization in the white dwarf."

All things in the Universe must change. Every star that hangs in the firmament, shining brightly with the light generated by atomic fusion, will one day run out of fuel for their fires and evolve into something new.

For the vast majority of stars – those below about eight times the mass of the Sun, and including the Sun – that something is a white dwarf star.

When the fuel runs out, the star's outer material is shucked into the surrounding space, and the remaining core, no longer supported by the outward pressure supplied by fusion, will collapse down into an ultradense object, around the size of Earth (or the Moon!), but packing in as much mass as 1.4 Suns.  READ MORE...

Milky Way Streaking

In 2017, astronomers noticed a star streaking out of the Milky Way at nearly 2 million mph (3.2 million km/h) — roughly four times faster than our sun orbits — and flying against the direction in which most stars trek around the galactic center. 

It's also made of completely different star stuff, mostly heavy, "metallic" atoms rather than the usual light elements. 

LP 40-365, as it was called, was as eye-catching as a wooden car barreling up the interstate against traffic at hundreds of miles per hour.

"It is exceptionally weird in a lot of different ways," said study lead author J.J. Hermes, an astronomer at Boston University.

The star moves so quickly that it's headed out of our galaxy for good, which astronomers have taken as evidence that the metallic explorer was launched here by a cosmic catastrophe — a supernova. 

But they couldn't tell how the supernova had sent it flying. Was LP 40-365 a piece of the exploded star itself? Or was it a partner star flung clear by the shockwave associated with star explosions? 

A new analysis of old data finds that the star — called a white dwarf — spins about its axis at a leisurely pace — a hint that it is indeed a piece of stellar debris (not a partner star) that managed to survive one of the galaxy's most violent and mysterious events.

"We can now connect this star to the shrapnel from an exploded white dwarf with a lot more confidence," said Hermes.  READ MORE