Diamond planets may be more common than astronomers thought

May 13, 2014 by Eric Gershon
Diamond planets may be more common than astronomers thought
Diamond planets may be more common than astronomers thought. Credit: Haven Giguere

(Phys.org) —Carbon-rich planets may be more common than previously thought, according to new research by Yale University astronomers.

Some of these planets, all located far beyond Earth's solar system, could contain vast deposits of graphite or diamonds, and their apparent abundance prompts new questions about the implications of carbon-intense environments for climate, , and other geological processes, as well as for life.

"Despite the relatively small amount of carbon on Earth, carbon has been critical for the emergence of life and the regulation of our climate through the carbon-silicate cycle," said Yale doctoral candidate John Moriarty, who led the research, recently published in Astrophysical Journal. "It's an open question as to how carbon-rich chemistry will affect the habitability of exoplanets. We hope our findings will spark interest in research to help answer these questions."

Moriarty collaborated with Yale astronomy professor Debra Fischer and Nikku Madhusudhan, a former Yale postdoctoral researcher now at Cambridge University.

Exoplanets are planets outside Earth's . In October 2012 Madhusudhan published a paper arguing that 55 Cancri e, a rocky exoplanet twice Earth's size, is likely covered in graphite and diamond.

Astronomers generally believe that rocky exoplanets are composed—as Earth is—largely of iron, oxygen, magnesium, and silicon, with only a small fraction of carbon. In contrast, carbon-rich planets could have between a small percentage and three-quarters of their mass in carbon. (Earth has 0.005%.)

Moriarty, Madhusudhan, and Fischer developed an advanced model for estimating exoplanet composition. Previous models were based on static snapshots of the gaseous pools (or disks) in which planets form. Their new model tracks changes in the composition of the disk as it ages.

The researchers found that, in disks with carbon-oxygen ratios greater than 0.8, carbon-rich planets can form farther from the center of the disk than previously understood. They also found that carbon-rich planets can form in disks with a carbon-oxygen ratio as low as 0.65 if those planets form close to their host star.

Previous models predicted carbon-rich could only form in disks with carbon-oxygen ratios higher than 0.8. This is important, the researchers said, because there are many more stars with carbon-oxygen ratios greater than 0.65 than there are with carbon-oxygen ratios greater than 0.8.

Said Madhusudhan, "Our study shows that extraterrestrial worlds can be extremely diverse in their chemical compositions, including many that are drastically different from our earthly experience."

The paper, published May 6, is titled "Chemistry in an evolving protoplanetary disk: Effects on terrestrial planet composition."

The Yale Center for Astronomy and Astrophysics provided support for the research.

There are more than 1,000 confirmed exoplanets and more than 3,000 exoplanet "candidates."

"An important question is whether or not our Earth is a typical rocky planet," said Fischer. "Despite the growing number of exoplanet discoveries, we still don't have an answer to this question. This work further expands the range of factors that may bear on the habitability of other worlds."

Explore further: First carbon-rich exoplanet discovered

Related Stories

First carbon-rich exoplanet discovered

December 8, 2010

(PhysOrg.com) -- A team led by a former postdoctoral researcher in MIT's Department of Earth, Atmospheric and Planetary Sciences and the MIT Kavli Institute for Astrophysics, recently measured the first-ever planetary atmosphere ...

New theoretical models aid the search for Earth-like planets

November 14, 2013

Researchers from Bern have developed a method to simplify the search for Earth-like planets: By using new theoretical models they rule out the possibility of Earth-like conditions, and therefore life, on certain planets outside ...

How life could have produced most minerals on Earth

April 30, 2014

While astronomers are trying to figure out which planets they find are habitable, there are a range of things to consider. How close are they to their parent star? What are their atmospheres made of? And once those answers ...

Recommended for you

Aging star's weight loss secret revealed

November 25, 2015

A team of astronomers using ESO's Very Large Telescope has captured the most detailed images ever of the hypergiant star VY Canis Majoris. These observations show how the unexpectedly large size of the particles of dust surrounding ...

Scientists detect stellar streams around Magellanic Clouds

November 23, 2015

(Phys.org)—Astronomers from the University of Cambridge, U.K., have detected a number of narrow streams and diffuse debris clouds around two nearby irregular dwarf galaxies called the Magellanic Clouds. The research also ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.