By Robert Roy Britt
Senior Science Writer
08 February 2005
The solid planets in our solar system are made mostly of silicates. Rock, basically. A new study shows that planets around some other stars might be made mostly of carbon instead. Deep inside such worlds, where pressures are intense, the carbon would make layers of diamonds that could be miles thick.
The rich-sounding worlds are modeled after a certain type of space rock, known as the carbonaceous chondrite, which are thought to be broken bits of asteroids. Many of them have been collected on Earth.
"These meteorites contain large quantities of carbon compounds such as carbides, organics, and graphite, and even the occasional tiny diamond," Marc Kuchner of Princeton University said in a teleconference with reporters Monday evening from an extrasolar planet conference in Aspen.
The idea builds on other reasonable theories.
The planets in our solar system formed from a disk of gas and dust left behind from the Sun's formation. In regions where there was extra carbon or a lack of oxygen, carbon compounds like graphite and carbides would condense out of the mix, instead of stone.
Carbides are a ceramic used to line the cylinders of engines. They can take the heat of being very close to a star.
Kuchner and his colleague, Sara Seager of the Carnegie Institute of Washington, figure that concept fits nicely with discoveries of planets around other stars, including some that are surprisingly close to their host stars -- much closer than Mercury is to the Sun. Carbon planets could survive at high temperatures near a star, they say.
Read more: http://www.space.com/scienceastronomy/diamond_planets_050208.html