1. They might be rich in diamonds
A thick layer of diamond, provided there’s enough pressure, could exist under a topping of carbon in the form of the mineral, graphite, which can be found in the very lead of pencils. Diamonds might also erupt from volcanoes on the surface of carbon planets, spitting out mountains of these jewels.
2. We may have found candidates
We think that there are at least two possibilities of carbon worlds, or diamond planets, out of the incredible number of exoplanets that we have detected so far. One could be around pulsar PSR 1257+12 which formed from the disruption of a star churning out carbon. A second might be the planet we know as 55 Cancri e, weighing in at around 7.8 Earth masses and whipping around its Sun-like star 55 Cancri A – a star that forms part of the binary 55 Cancri – at a relatively short 18 hours. This particular candidate has shown some evidence of being bathed in graphite or diamond rather than the water and granite that we’re used to here on Earth.
3. They have got no snow beyond the snow-line
It is thought that comets and possibly asteroids delivered water to our planet early in the history of the Solar System. These distant travellers are thought to have begun their journey far beyond Earth, way past a boundary known as the snow-line before smashing into its surface and depositing their water, previously locked up as ice. Yet overlaying our Solar System’s model over planetary systems containing carbon worlds, astronomers have discovered that water, no matter which body it’s on, just disappears beyond the snow-line.
What this now means is that carbon worlds are home to a surface of frozen organic materials such as tar or methane as well as choking carbon monoxide. You would be hard pressed to find oceans of water on their surfaces and this is because the overly abundant carbon found in developing star systems would snag any oxygen, refusing to let water form, causing them to come up quite dry.
4. Hydrocarbon rain might drizzle from their smoggy atmospheres
If a carbon world has a temperature cool enough – at around 77 degrees Celsius – a cycle would be kick-started where rain, made of organic materials, would shower down onto the surface from an atmosphere abundant in carbon dioxide or carbon monoxide along with some other gases. Such a combination of gases would cause their skies to be incredibly thick with smog.
5. They are likely to be on the increase
These worlds are probably to be close to the core of our Galaxy or in the globular clusters found orbiting it. This is because you are most likely to find old stars in these places. When these ancient stars pass on, they spew out gigantic amounts of carbon and go on to create these unusual planets. All stars must end, so it makes sense that, as more and more generations are snuffed out, we will find more and more carbon worlds.
Image Credit: NASA