The study of exoplanets—worlds orbiting distant stars—is still in its early days. Yet already researchers have found hundreds of worlds with no nearby analogue: giants that could steamroll Jupiter; tiny pebbles broiling under stellar furnaces; puffy oddballs with the density of peat moss. Still other exoplanets might look familiar in broad-brush, only to reveal a topsy-turvy realm where rare substances are ordinary, and vice versa.
Take carbon, for instance: the key constituent of organic matter accounts for some of humankind's most precious materials, from diamonds to oil. Despite its outsize importance, carbon is uncommon—it makes up less than 0.1 percent of Earth's bulk.
On other worlds, though, carbon might be as common as dirt. In fact, carbon and dirt might be one and the same. An exoplanet 40 light-years away was recently identified as a promising candidate for just such a place—where carbon dominates and where the pressures in the planet's interior crushes vast amounts of the element into diamond.
The planet, known as 55 Cancri e, might have a crust of graphite several hundred kilometers thick. “As you go beneath that, you see a thick layer of diamond,” says astrophysicist Nikku Madhusudhan, a postdoctoral fellow at Yale University. The crystalline diamond could account for a third of the planet's thickness.To read more, click here.