“At least one planet exists that is composed mostly of diamond.”

Officially named PSR J2322-2650b, this Jupiter-mass object appears to have an exotic helium-and-carbon-dominated atmosphere unlike any ever seen before. Soot clouds likely float through the air, and deep within the planet, these carbon clouds can condense and form diamonds.

Updated models from 2020-2025 indicate 55 Cancri e likely has a silicate-dominated composition with a possible steam or CO2 atmosphere, reducing support for the original diamond planet model based on refined stellar parameters and transit spectroscopy.

Planet Radius: 1.875 x Earth. Planet Type: Super Earth. Discovery Method: Radial Velocity. Planet Mass: 7.99 Earths. Discovery Date: 2004.

The new research suggests the planet has no water at all, and appears to be composed primarily of carbon (as graphite and diamond), iron, silicon carbide, and, possibly, some silicates. The study estimates that at least a third of the planet’s mass — the equivalent of about three Earth masses — could be diamond.

New radial velocity and TESS data suggest lower density consistent with rocky core plus envelope, not requiring extreme carbon enrichment; diamond fraction likely <10% if present.

An international team of scientists discovered a diamond planet with the help of the 64-metre Parkes radio telescope in Australia. The planet, known as PSR J1719-1438, orbits around an unusual, very dense star, a pulsar, and has a diameter of only 60,000 kilometres, half as big as Jupiter.

The universe just got a bit richer with the discovery of an apparent diamond-rich planet orbiting a nearby star, dubbed 55 Cancri e. This rocky world is only twice the size of Earth but has eight times its mass, and its surface temperatures reach an uninhabitable 3,900 degrees Fahrenheit (2,150 degrees Celsius), which, along with carbon, make perfect conditions for creating diamonds.

The detection of a carbon-rich atmosphere in exoplanet WASP-12b supports the possibility that rocky exoplanets could be composed of pure carbon rocks like diamond or graphite rather than the silica-based rock found in Earth. Future research will investigate what material might exist in their interiors.

The measured mass and radius of 55 Cancri e can however be reconciled by considering a composition based on carbon materials. As the latest measurements tend to discuss the likelihood of such an extremely carbon-rich composition, we think that 55 Cancri e constitutes a strong case... The mantle is solely composed of silicon carbide. SiC, surrounded by a pure carbon envelope. The carbon envelope may divide into graphite and diamond.

PSR J2322-2650b is one of the weirdest known exoplanets... has a chemical composition unlike any we've ever seen before and may be raining diamonds internally... scientists now believe the high pressures found inside the planet are likely to compress that carbon into diamonds.

The newly observed world has a stretched, lemon-like shape and may even contain diamonds deep inside... The extreme pressure inside the planet could cause that carbon to crystallize, potentially forming diamonds deep below the surface.

Super-Earth 55 Cancri e, which made headlines in 2012 as “the diamond planet,” needs to be reclassified as a sapphire planet, according to astronomers at the Universities of Zurich and Cambridge. Astrophysicist Caroline Dorn, the lead author of new research published in the British journal Monthly Notices of the Royal Astronomical Society (MNRAS), stated, “We are turning the supposed diamond planet into a sapphire planet.” Dorn and her team determined that new observations of 55 Cancri e, along with two other super-Earths, suggest they contain high quantities of aluminum oxide, the compound that makes up sapphire and ruby.

The planet, known as 55 Cancri e, is located around 41 light-years from the solar system and has a width almost twice that of Earth and a mass around nine times greater than our planet. This exoplanet is so dense that astronomers have hypothesized it to be composed of mostly carbon that's been compressed to diamond. Using the James Webb Space Telescope (JWST), astronomers have discovered that this scorching hot lava planet, believed to be composed of diamond, grew a second atmosphere after its star destroyed its first.

Carbon-rich planets are defined by a C/O ratio >0.8, and 55 Cancri e has been an archetype for this particular type of planet. Experimental data collected on binary Si-C and ternary Fe-Si-C systems under extreme pressure and temperature conditions provide insight into the stability and properties of components that are candidates as constituents of carbon-rich exoplanets.

The diamond planet hypothesis for 55 Cancri e originated from 2010 stellar composition studies suggesting a carbon-to-oxygen ratio greater than one. However, subsequent re-analysis of stellar data and atmospheric observations have cast doubt on whether 55 Cancri e is primarily composed of diamond, with current evidence suggesting it may be a rocky lava planet with a secondary atmosphere instead.

... planet made of diamonds. But what is Janssen actually like? If we ever prove it's existence... observations indicated the planet's atmosphere was only slightly thicker than Earth's and could contain both nitrogen and oxygen. But then in 2020, another study failed to detect any helium, and a 2012 study failed to...