The Diamond Planet: A Priceless Soaring Gem? Or a Myth?

The Diamond Planet, also known as Janssen and 55 Cancri e, sparkles so brightly you can see it from Earth with your unaided eye. However, that brightness doesn’t come from a diamond mass. 

Instead, the planet orbits so close to its host star that it looks like a giant orb of molten lava. 55 Cancri e orbits 65 times closer to its star than the Earth to the Sun. It is so close that the planet always has one side facing the star while the other experiences perpetual nighttime.

Clouds of atmospheric silicates float on the tidally-locked planet’s cooler, dark side. The skies then sparkle as the silicate vapor condenses and reflects the lava below. 

Keep reading to learn whether or not 55 Cancri e lives up to its name, the Diamond Planet. While no photos of this exoplanet exist, scientific artists attempt to illustrate it based on its composition and proximity to neighbors.

diamond planet
Artist’s Concept Credit: JPL/NASA

Do Diamond Planets Exist?

For a while after its discovery, exoplanet 55 Cancri e gained the name the Diamond Planet because scientists thought diamonds and graphite made up its composition.

A diamond planet is a type of planet composed primarily of carbon in the form of diamonds. These planets may exist in the universe due to the abundance of carbon and the extreme pressures and temperatures that can exist in certain parts of space.

The basic idea is that carbon transforms into diamonds if a planet has the proper high pressure and temperature conditions. But, of course, such a planet would be very different from Earth, with a solid, diamond-like surface and a different atmospheric composition.

While no diamond planet has been directly observed or confirmed, some exoplanets, planets that orbit around stars other than our sun, could be made primarily of diamond. However, more research and observation are needed to verify the existence and properties of actual diamond planets.

What is 55 Cancri e?

55 Cancri e resides about 40 light-years from Earth. Find this super-Earth exoplanet in the constellation of Cancer. Since its 2004 discovery, the Diamond Planet has been the subject of extensive research due to its unique characteristics.

It is approximately twice Earth’s size, with a mass of about eight times that of Earth. It is also one of the closest known exoplanets to its host star, Copernicus, with a year lasting only 18 hours. This proximity means that the planet is tidally locked, with one side permanently facing the star and the other in perpetual darkness.

The planet’s surface is composed of carbon, which led some scientists to speculate that it might be diamond covered. However, recent studies suggest that the planet’s atmosphere is primarily composed of hydrogen and helium, with some hints of other molecules, such as water vapor.

55 Cancri e is also notable for its extreme temperatures, reaching up to 3,630 degrees Fahrenheit (2,000 degrees Celsius) on its dayside. These temperatures make it one of the hottest exoplanets known to science. Additionally, the planet’s proximity to its star causes it to experience significant gravitational forces, creating its eccentric orbit.

Diamond Planet Facts

While scientists now believe that 55 Cancri e is not actually a diamond planet, they also think its atmosphere is thicker than Earth’s. It may even contain some of the same Earth-atmosphere ingredients. 

Data from a 2017 Spitzer Space Telescope study shows the exoplanet may have a lava surface. Since the planet is so close to its star, one side always faces it. The other side always stays dark. 

  • Planet type: Super Earth
  • Discovery date: 2004
  • Mass: 8.08 Earths
  • Planet radius: 1.875 x Earth, approximately double Earth’s size
  • Orbital radius: 0.01544 AU
  • Orbital period: 0.7 days
  • Eccentricity: 0.05
  • Detection method: Radial velocity
  • The surface is covered entirely in lava.
  • Planet images look like a fiery red ball.

Does 55 Cancri e Have Diamonds?

A 2012 Yale University study suggested that 55 Cancri e has a carbon makeup. Lead researcher Nikku Madhusudhan believed the planet’s surface was covered primarily in diamond and graphite, differing from Earth’s water and graphite surface. 

The model included iron and silicon carbides, with the possibility of silicates. The study also estimates a third of the planet’s mass could be diamond. That’s about three Earth masses of diamonds.

55 Cancri e
Artist Conception Credit: Haven Giguere

In 2017 Yale researchers and scientists published another study proposing rocky planets orbiting stars could have thick diamond layers under their surfaces. They believe carbon-rich planets likely form from silicon carbide. High internal temperatures decompose the silicon carbide into separate layers of silicon and diamond.

In the 20 years before the study, astronomers discovered more than 3,500 exoplanets. Many fall into the super-Earth classification with masses up to 10 times that of Earth. High surface temperatures result from the close orbit of many of these super-Earths to their stars. So researchers think interior temperatures are hot enough to decompose silicon carbide.

The result is a potential increase in the number of diamond planets.

multiple diamond planets
Illustration Credit: Haven Giguere

How Much Is a Diamond Planet Worth?

In 2012, Forbes estimated the Diamond Planet’s worth at $26.9 nonillion. So let’s see how that number looks.

  • $26.9 followed by 30 zeros
  • $269,000,000,000,000,000,000,000,000,000,000
  • A trillion has 12 zeros
  • A quadrillion has 15 zeros
  • 384 quadrillion times more than Earth’s GDP

Forbes contributor, Peter Cohan, determined the planet’s worth by:

  1. Multiplying Earth’s mass by three.
    • 17,920,800,000,000,000,000,000,000 kilograms
  2. Determining the raw diamond value per kilogram
    • $1.5 million
  3. To arrive at the Diamond Planet’s raw worth in 2012
    • $26,881,200,920,800,000,000,000,000,000,000

Of course, with the accessibility of so many diamonds, the price of diamonds would drastically reduce, instantly cratering the Diamond Planet’s worth. Easy come, easy go.


Overall, the Diamond Planet – 55 Cancri e is a fascinating exoplanet that continues to capture the attention of scientists and the public alike. Further studies of this intriguing world could help us better understand planetary systems’ formation and evolution beyond our own.

As far as current scientific understanding goes, there is no evidence to suggest the existence of diamond planets. Furthermore, while some exoplanets are composed primarily of carbon, it is unlikely that these planets would be made entirely of diamond.

Diamond is a form of carbon created under very high pressure and temperature conditions, such as those found deep within the Earth’s mantle. While some exoplanets may have conditions that could develop diamonds, it is unlikely that entire planets are diamonds.

Additionally, the extreme conditions required to form diamonds would likely be inhospitable to life as we know it, so even if diamond planets exist, it is unlikely that they would support any living organisms.

In summary, while diamond planets may be fascinating, no scientific evidence fully supports their existence.