National Geographic Daily News
An illustration of an exoplanet with a diamond crust.

An illustration of 55 Cancri e shows a surface of mostly graphite surrounding a thick layer of diamond.

Illustration courtesy Haven Giguere, Yale

Andrew Fazekas

for National Geographic News

Published October 11, 2012

The universe just got a bit richer with the discovery of an apparent diamond-rich planet orbiting a nearby star.

Dubbed 55 Cancri e, the rocky world is only twice the size of Earth but has eight times its mass—classifying it as a "super Earth," a new study says. First detected crossing in front of its parent star in 2011, the close-in planet orbits its star in only 18 hours. As a result, surface temperatures reach an uninhabitable 3,900 degrees Fahrenheit (2,150 degrees Celsius)—which, along with carbon, make perfect conditions for creating diamonds.

NASA's Spitzer Space Telescope collected data on the planet's orbital distance and mass, and resulting computer models created a picture of 55 Cancri e's chemical makeup.

"Science fiction has dreamed of diamond planets for many years, so it's amazing that we finally have evidence of its existence in the real universe," said study leader Nikku Madhusudhan, a postdoctoral researcher at Yale University.

"It's the first time we know of such an exotic planet that we think was born mostly of carbon—which really makes this a fundamental game-changer in our understanding of what's possible in planetary chemistry."

(See "'Diamond' Planet Found; May Be Stripped Star.")

At only 40 light-years away, in the northern constellation Cancer, the gemlike planet sits relatively near Earth. In dark skies, 55 Cancri e's host star is clearly visible to the naked eye. (See gem pictures.)

Diamond Planet Has Odd Chemistry

The new models fit with previous studies that showed 55 Cancri e's parent star was abundant in carbon—much more so than our sun.

"If we make the assumption that the star and its surrounding planets are all born from the same primordial disk of material, then it makes sense that the entire planetary system would be carbon rich," said Madhusudhan, whose study will appear in an upcoming issue of the journal Astrophysical Journal Letters.

Princeton astronomer David Spergel believes the diamond-planet find probably represents the first discovery of a whole new class of planets whose chemistry has never been encountered. (Related: "'Diamond Planets' Hint at Dazzling Promise of Other Worlds.")

"Unlike our solar system, which is dominated by oxygen and silicates, this planetary system is filled with carbon," said Spergel, who was not involved in the new study.

"While it's still unknown exactly what implication this will have on our understanding of evolution of planetary systems," he said, "there's no doubt it is an important step towards understanding the full diversity of planets."

6 comments

How to Feed Our Growing Planet

  • Feed the World

    Feed the World

    National Geographic explores how we can feed the growing population without overwhelming the planet in our food series.

See blogs, stories, photos, and news »

The Innovators Project

  • Brave Sage of Timbuktu

    Brave Sage of Timbuktu

    Abdel Kader Haidara had made it his life's work to document Mali's illustrious past. When the jihadists came, he led the rescue operation to save 350,000 manuscripts.

See more innovators »

Phenomena

See more posts »

Latest News Video

See more videos »

See Us on Google Glass

Shop Our Space Collection

  • Be the First to Own <i>Cosmos: A Spacetime Odyssey</i>

    Be the First to Own Cosmos: A Spacetime Odyssey

    The updated companion book to Carl Sagan's Cosmos, featuring a new forward by Neil deGrasse Tyson is now available. Proceeds support our mission programs, which protect species, habitats, and cultures.

Shop Now »