New Evidence Suggests Diamond Exoplanets May Exist

While astronomers have already come across thousands of exoplanets—which are planets outside our solar system—their properties are still quite mysterious. Astronomers think, for example, that some carbon-rich exoplanets may largely be made up of diamonds. Researchers at Arizona State University and the University of Chicago have found new evidence supporting that possibility.

Scientists have found new evidence supporting the idea there may be planets made mostly of diamond.


Syfy Wire picked up on news of the new evidence supporting the existence of diamond planets. The researchers responsible for the findings, including lead author Harrison Allen-Sutter of ASU’s School of Earth and Space Exploration, outlined their work in a paper recently published in The Planetary Science Journal.

In the study, the researchers say astrophysical measurements have shown that some stars have sufficiently high carbon-to-oxygen ratios to host planets with similar compositions. These planets, relatively heavy in carbon instead of silicon, when formed under the right conditions, could hypothetically have an interior made of diamonds. (The image below is an example of one of those planets, 55 Cancri e.)

Scientists have found new evidence supporting the idea there may be planets made mostly of diamond.


To figure out if these carbon-rich planets could have diamond interiors, the team performed an experiment. The researchers first immersed silicon carbide, which would be found in abundance on one of these worlds, in water. They then compressed the immersed chemical compound between diamonds at high pressures. Simultaneously, the researchers blasted the silicon carbide with a laser. As the team expected, the heat and high pressure did indeed cause the silicon carbide to react with the water. It then, in turn, transformed into diamonds and silica.

Allen-Sutter et al. say these results show that if carbon-rich planets can develop water during their formation, or through later delivery by say, a comet, they could oxidize. As a result, they would have a mineralogy dominated by silicates and diamonds. (For reference, Earth’s interior is rich in oxygen, but very poor in carbon; it also has roughly 150 times more silicon than carbon in its crust.)

Scientists have found new evidence supporting the idea there may be planets made mostly of diamond.


Unfortunately, if these diamond exoplanets do exist, they likely don’t possess the properties conducive for life. “Regardless of habitability,” Allen-Sutter says, “this is [still] one additional step in helping us understand and characterize our ever-increasing and improving observations of exoplanets.”

What do you think about this experiment to determine the feasibility of the existence of diamond exoplanets? Do you think we’ll find giant worlds made of the precious crystal structures in our lifetimes? Let’s talk pricey planet cores in the comments!

Feature image: Shim/ASU/Vecteezy