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: How life could have produced most minerals on Earth

add to favorites email to friend print save as pdf

Related Stories

First carbon-rich exoplanet discovered

Dec 08, 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 ...

How life could have produced most minerals on Earth

Apr 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 ...

Recommended for you

Can astronomy explain the biblical Star of Bethlehem?

Dec 24, 2014

Bright stars top Christmas trees in Christian homes around much of the world. The faithful sing about the Star of Wonder that guided the wise men to a manger in the little town of Bethlehem, where Jesus was ...

Hubbles spies the beautiful galaxy IC 335

Dec 24, 2014

This new NASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. IC 335 is part of a galaxy group containing three other galaxies, and located in the Fornax ...

Image: Multicoloured view of supernova remnant

Dec 22, 2014

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Ultra-luminous X-ray sources in starburst galaxies

Dec 22, 2014

Ultra-luminous X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. ULXs are rare. Most galaxies (including ...

When a bright light fades

Dec 22, 2014

Astronomer Charles Telesco is primarily interested in the creation of planets and stars. So, when the University of Florida's giant telescope was pointed at a star undergoing a magnificent and explosive death, ...

User comments : 0

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.