The Coldest White Dwarf Ever Discovered Is Also An Earth-Sized Diamond

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Astrophysicists have discovered what might be the coldest, dimmest white dwarf star ever seen, it is so cold that its carbon has crystallized, not unlike a diamond. The work was distributed in the Astrophysical Journal this week. White dwarfs are end-state stars that have shrunken to custom hot, tremendously dense, Earth-sized objects composed generally of carbon and oxygen. Though they can be as massive as the sun, white dwarfs are so dense they're roughly about the size of Earth. After they consume their nuclear fuel, white dwarfs will continue to cool and weaken slowly over the period of billions of years. This is what will our sun finally turn out to be. Things this blurry are certainly very hard to detect. Merging observations from a range of sources, counting the Green Bank Telescope in West Virginia and also the Very Long Baseline Array at Mauna Kea, a group directed by David Kaplan at the University of Wisconsin-Milwaukee was able to do so since the object was situated in a binary star system.
Image Credit: Artist impression of a white dwarf star in orbiting a pulsar PSR J2222-0137 / B. Saxton (NRAO/AUI/NSF) 
The 11-billion-year-old, unusually cool white dwarf was revealed alongside with its pulsar companion, PSR J2222-0137. Pulsars are quickly rotating neutron stars, the leftovers of massive stars that detonated as supernovas. As these stars rotate, beams of radio waves stream from the ends of its magnetic field, and when one of these rays’ bend across Earth, radio telescopes can detect the pulsation of the waves.

Scientists essentially detected the pulsar first. It was revolving more than 30 times a second and seemed to be gravitationally bound to a partner star, which they originally thought was additional neutron star. The two circle each other once every 2.45 days. Explanations and observations of the pulsar over the next two years exposed its position and distance: 900 light-years from Earth and in the Aquarius constellation.  By learning how the gravity of the partner star distorted space and triggered interruptions in the radio signal, the group was able to compute both the mass of the pulsar which is about 1.2 times that of the sun and the companion was 1.05 times more massive that of the sun. That’s when they recognized the other object couldn’t be another neutron star: The orbits were too arranged for a second supernova to have occurred. BartDunlap from the University of North Carolina at Chapel Hill describes in a newsrelease. “Our final image should show us a companion 100 times fainter than any other white dwarf orbiting a neutron star and about 10 times fainter than any known white dwarf, but we don’t see a thing. If there’s a white dwarf there, and there almost certainly is, it must be extremely cold.”

Fairly cold, to be clear. The white dwarf couldn’t be over 2,700 degrees Celsius; the core of the sun is 5,000 times hotter. Astrophysicists consider such a cool earliest stellar leftover would be mostly crystallized carbon, which makes it, a diamond.

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