WASHINGTON—Twinkling stars are not the only diamonds in the sky.
Scientists reported on Thursday the existence of a “diamond planet” twice the size of Earth and eight times its mass, zooming around a nearby star.
In fact, this is not the first diamond planet ever discovered, but it is the first found orbiting a sun-like star and whose chemical makeup has been specified.
The discovery means that distant rocky planets can no longer be assumed to have chemical constituents, interiors, atmospheres or biologies similar to those of Earth, said lead researcher Nikku Madhusudhan, a Yale postdoctoral researcher in physics and astronomy.
The planet was first observed last year—but researchers initially assumed it was similar in its chemical makeup to Earth.
Vastly different from earth
It was only after a more detailed analysis that the French-American research team determined that the planet, dubbed 55 Cancri e, is vastly different from our own.
The planet “appears to be composed primarily of carbon (as graphite and diamond), iron, silicon carbide, and, possibly, some silicates,” the authors wrote in a statement ahead of their findings’ publication in the US journal Astrophysical Journal Letters.
“The surface of this planet is likely covered in graphite and diamond rather than water and granite,” noted Madhusudhan, who conducted the study with Kanani Lee and Olivier Mousis at the Institut de Recherche en Astrophysique et Planetologie in Toulose, France.
In fact, the planet appears to have no water at all. As much as a third of the planet’s substantial mass could be made of diamond, a super-dense compound of carbon.
“This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth,” Madhusudhan said.
In comparison, Earth’s interior is rich in oxygen and very poor in carbon, explained study coauthor Lee of Yale.
The researchers estimated the planet’s radius with data collected while it was transiting in front of its star.
That information, combined with an estimate of its mass, was used to model the planet’s chemical composition, based on a calculation of just what elements and compounds could result in that specific size and mass.
18 hours: One year
The planet’s orbit around its star is lightning fast—a year lasts just 18 hours. And because it is so close to its star, surface temperatures average 3,900 degrees Fahrenheit (2,148 Celsius), rendering it completely inhospitable to life.
But the planet—just 40 lightyears away from Earth in the Cancer constellation—opens new avenues for studying geochemical and geophysical processes of Earth-sized planets outside our solar system.
The high levels of carbon may have implications on how volcanoes and earthquakes work and how mountains form—and add to the growing body of evidence that planets are far more numerous and varied than initially imagined.
“Stars are simple—given a star’s mass and age, you know its basic structure and history,” said David Spergel, a Princeton University astronomer.
“Planets are much more complex. This ‘diamond-rich super-Earth’ is likely just one example of the rich sets of discoveries that await us as we begin to explore planets around nearby stars.”
“Nearby” is a relative concept in astronomy. Any fortune-hunter not dissuaded by “The Diamond as Big as the Ritz,” F.Scott Fitzgerald’s jazz age morality tale of thwarted greed, will find Cancri e about 40 light years, or 230 trillion miles, from Park Avenue. With a report from Reuters