When stars use up their nuclear fuel, they turn into “white dwarf” stars. When white dwarf stars cool down, they crystallize.
In 2004, the Harvard-Smithsonian Center for Astrophysics discovered a cooled white dwarf 50 light years away from Earth.
At the core of that cooling star is a diamond 2,500 miles across, which weighs 5 million trillion trillion pounds, or around 2 thousand trillion trillion tons, or approximately 10 billion trillion trillion carats.
As the Harvard-Smithsonian Center explained:
A white dwarf is the hot core of a star, left over after the star uses up its nuclear fuel and dies. It is made mostly of carbon.
For more than four decades, astronomers have thought that the interiors of white dwarfs crystallized, but obtaining direct evidence became possible only recently.
“The hunt for the crystal core of this white dwarf has been like the search for the Lost Dutchman’s Mine. It was thought to exist for decades, but only now has it been located,” says co-author Michael Montgomery (University of Cambridge).
The white dwarf studied by Metcalfe, Montgomery, and Antonio Kanaan (UFSC Brazil), is not only radiant but also harmonious. It rings like a gigantic gong, undergoing constant pulsations.
“By measuring those pulsations, we were able to study the hidden interior of the white dwarf, just like seismograph measurements of earthquakes allow geologists to study the interior of the Earth. We figured out that the carbon interior of this white dwarf has solidified to form the galaxy’s largest diamond,” says Metcalfe.
Amazingly, according to the Harvard-Smithsonian team, our sun will also eventually become a giant diamond:
Our Sun will become a white dwarf when it dies 5 billion years from now. Some two billion years after that, the Sun’s ember core will crystallize as well, leaving a giant diamond in the center of our solar system.
“Our Sun will become a diamond that truly is forever,” says Metcalfe.
Last month, scientists discovered a planet whose core was diamond. As Reuters reports:
Astronomers have spotted an exotic planet that seems to be made of diamond racing around a tiny star in our galactic backyard.
The new planet is far denser than any other known so far and consists largely of carbon. Because it is so dense, scientists calculate the carbon must be crystalline, so a large part of this strange world will effectively be diamond.
“The evolutionary history and amazing density of the planet all suggest it is comprised of carbon — i.e. a massive diamond orbiting a neutron star every two hours in an orbit so tight it would fit inside our own Sun,” said Matthew Bailes of Swinburne University of Technology in Melbourne.
Lying 4,000 light years away, or around an eighth of the way toward the center of the Milky Way from the Earth, the planet is probably the remnant of a once-massive star that has lost its outer layers to the so-called pulsar star it orbits.
And as Scientific American notes, Earth’s gold came mainly from meteorites:
It appears that a rain of meteors nearly 4 billion years ago peppered the Earth’s exterior with precious metals. So says a study in the journal Nature. [Matthias Willbold, Tim Elliott and Stephen Moorbath, "The tungsten isotopic composition of the Earth’s mantle before the terminal bombardment"]
[Gold] wasn’t even on the Earth until after the core formed. Isotope concentrations in rock samples of different ages indicate that the composition of the Earth’s mantle changed after the planet was blasted with meteors 3.9 billion years ago. That bombardment coated our home with a thin veneer of riches. Which means that the gold in them thar hills is older than the hills.
So we will eventually be able to mine diamonds from cooling stars – or better yet, the planets they leave behind – and gold and other precious metals from meteorites.
But it may take us a couple of thousand years to build the technology to do so …