Astronomers Discover Earth-Sized Diamond

ygslash (893445) writes Astronomers at the National Radio Astronomy Observatory announced that they have discovered what appears to be the coolest white dwarf ever detected. The white dwarf is formerly a star similar to our own sun which, after expending all of its fuel, has cooled to less than a chilly 3000 degrees Kelvin and contracted to a size approximately the same as Earth. A white dwarf is composed mostly of carbon and oxygen, and the astronomers believe that at that temperature it would be mostly crystallized, forming something like a huge diamond.

Comments

Just don't tell De Beers

[JoshuaZ]

Considering that the high price of diamonds is a combination of the De Beers monopoly together with their massive PR campaigns to a) make people use diamonds as formal symbols of affection and b) to make people unwilling to sell them second-hand once they've been owned, they should be worried. On the other hand, this is 900 light years away, so maybe they'll just lobby against any research into FTL travel.

Kelvin

[Anonymous Coward]

not "degrees Kelvin"

Re:DIAMONDS DO NOT WORK THAT WAY

[Required Snark]

Warning: ACTUAL PHYSICS, not typical Slashdot half-assed speculation.

This class of white dwarf stars are a mixture of primarily oxygen and carbon. Depending on the mass the amount of carbon and oxygen are roughly the same, but sometimes there is more oxygen. As the star cools it goes through a phase transition where the core becomes crystallized. This releases heat through two mechanisms: heat of crystallization and the release of gravothermal energy.

The inner crystallized section is enhanced in oxygen. The outer fluid mantel is enriched in carbon. Calling this a diamond is simply wrong. Perhaps at some point in the distant future one of these will cool and part of it will become a form of crystal carbon, but considering that the cooling time without mantle carbon crystallization is on the order of 10 Gigayears, it is not likely this has happened yet considering that the universe is around 13.6 gigayears old.

http://iopscience.iop.org/0004-637X/486/1/413/fulltext/34903.text.html

The Cooling of CO White Dwarfs: Influence of the Internal Chemical Distribution

White dwarfs are the remnants of stars of low and intermediate masses on the main sequence. Since they have exhausted all of their nuclear fuel, their evolution is just a gravothermal process. The release of energy only depends on the detailed internal structure and chemical composition and on the properties of the envelope equation of state and opacity; its consequences on the cooling curve (i.e., the luminosity vs. time relationship) depend on the luminosity at which this energy is released.

The internal chemical profile depends on the rate of the 12C(, )16O reaction as well as on the treatment of convection. High reaction rates produce white dwarfs with oxygen-rich cores surrounded by carbon-rich mantles. This reduces the available gravothermal energy and decreases the lifetime of white dwarfs.

In this paper we compute detailed evolutionary models providing chemical profiles for white dwarfs having progenitors in the mass range from 1.0 to 7 M, and we examine the influence of such profiles in the cooling process. The influence of the process of separation of carbon and oxygen during crystallization is decreased as a consequence of the initial stratification, but it is still important and cannot be neglected. As an example, the best fit to the luminosity functions of Liebert et al. and Oswalt et al. gives an age of the disk of 9.3 and 11.0 Gyr, respectively, when this effect is taken into account, and only 8.3 and 10.0 Gyr when it is neglected.