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Tech Note: New Diamond Planet

Illustration of the interior of 55 Cancri e showing a sparkly diamond layer. (Photo: Haven Giguere)

A U.S.-French research team has reported the discovery of 55 Cancri e – a planet that is largely made out of diamonds and is 40 light years away from earth.

STOP. Before you start planning a trip to 55 Cancri e, space travel has not yet entered the commercial phase, and you can’t catch a ride on any of space shuttles because they have all been retired.

The other large problem that one would need to overcome is that the newly discovered 55 Cancri e, better known as the diamond planet, is also not easy to get to in the foreseeable future. Since the planet is 40 light years away, it would take 40 years to reach even if you were traveling at the speed of light.  We aren’t close to that speed today.  As a reminder, a light year is a unit of length equal to just under 10 trillion kilometers or about 6 trillion miles. The International Astronomical Union defines a light-year as the distance that light travels in a vacuum in one Julian (365.25 days) year. [Ref 1]

Discovering This New Planet

Artist impression of Earth compared to 55 Cancri e with a radius just over twice that of Earth. (Source: Wikipedia)

The new planet has been defined as an extrasolar planet that orbits the star 55 Cancri A.  When comparing the new planet to earth, its mass is about 7.8 times that of earth and about twice the diameter. [Ref 2]  My first thoughts for the new planet was that it was discovered within the last two weeks. Not true. The diamond planet was first discovered on August 30, 2004. However, until the 2010 observations and re-calculation, it was thought that this planet took about 2.8 days to orbit the star. In October 2012, it was announced that 55 Cancri e could be a carbon planet. Therefore, scientists have known about the planet for at least six years, however, knowledge of its content has just been recently confirmed.

Up until this recent discovery, it was assumed that rocky planets elsewhere in the universe are earthlike – composed of oxygen-rich mineral and rocks and abundant in water and oxygen.  However, this discovery gives an indication of what planets that formed around other stars could be like.

A Different Planet

Star map showing the planet-hosting star 55 Cancri in the constellation of Cancer. The star is visible to the naked eye. (Image:Nikku Madhusudhan using Sky Map Online) Source: Voice of America

According to Yale researcher Nikku Madhusudhan, “It is different because rocky planets in the solar system, such as Earth, are composed mostly of oxygen-rich compounds such as silicates, whereas carbon is very rare (less than 0.1 percent). On the other hand 55 Cancri e can have a substantial amount of carbon, even 30 percent or more. The difference in composition can lead to different geochemical and geophysical processes than what we see on solar system planets.” [Ref 3]

Based on our study, the planet 55 Cancri e is expected to be dominated by pure carbon in its outer layers. And, the most stable forms of pure carbon under high pressures of planetary interiors are graphite and diamond. So, it is expected that the surface of the planet is likely covered in graphite and diamond.

Madhusudhan reports that the new data for the diamond planet also suggests it has no water at all and is primarily made up of carbon – such as graphite and diamond – as well as iron, silicon carbide, and possibly some silicates. It is also extremely hot on the surface.

Further Study

Two possible follow up observations are being proposed. The first thing that needs to happen is to confirm if the planet has an atmosphere. If it does, its composition will need to be defined. Carbon-rich molecules in the atmosphere will be a strong indication of a carbon-rich interior. Second, the star chemical composition needs more accuracy to confirm the star is also indeed carbon-rich. A carbon-rich star indicates that the planet formed in a carbon-rich environment just like its star, and hence its’ carbon-rich interior composition becomes more plausible.

Yale geology and geophysics professor Kanani Lee, another author of the study states, “The carbon-rich composition of 55 Cancri e’s suggests the presence of large amounts of diamond on the planet. Since the planet’s orbiting period is 18 days as opposed to Earth’s 365 days, the surface temperature of the planet is approximately 4000 degrees Farenheit, she added. These high temperature and high pressure conditions favor diamond formation, she added.”[Ref 4]

What does this all mean? It means we continue to know more about the universe as new information, and in this case, planets are discovered. My May 2, 2012 post, Mining for Asteroids, discussed collecting carbon, mineral, and other materials including water from asteroids. Perhaps this new discovery will help identify additional carbon-rich planets that are not as far away, and may have some valuable mineral content that could be mined someday.


  1. Definition of light-year, Wikipedia, www.wikipedia.org
  2. Voice of America, Scientists Discover Planet covered in Diamonds, in Science World, October 22, 2012, http://blogs.voanews.com/science-world/2012/10/22/scientists-discover-planet-covered-in-diamonds/
  3. Discovery of Diamond Planet Opens A New Rocky World, Bhaskar Prasad, International Busienss Times, http://www.ibtimes.com/discovery-diamond-planet-opens-new-rocky-world-847633, October 17, 2012
  4. Diamond Planet Far, Far Away, Eric Xaio, October 23, 2012, Yale Daily News (online edition),  http://www.yaledailynews.com/news/2012/oct/23/diamond-planet-far-far-away/

About Vi Brown

Vi is principal and CEO of Prophecy Consulting Group, LLC, an Arizona firm that provides business and engineering services to private and public clients. Prior to establishing her consulting practice in 2001, Vi worked with Motorola, Maricopa County Government, Pacific Gas & Electric, CH2M Hill, and Procter & Gamble. As an adjunct faculty member, Vi teaches undergraduate calculus classes and graduate level environmental courses. She is also a professional speaker.


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