Here in the Solar System we have a rather interesting variety of planets, but they are limited by the composition of our Sun. Since planets, moons, asteroids and other bodies are made of what is left over after the Sun has finished forming, we thinks their chemistry is related to our host.
But not all stars are made of the same substance as our Sun, which means that out there in the vast expanses of our galaxy, we can expect to find wildly different exoplanets from the offer in our small Solar System.
For example, carbon-rich stars compared to our Sun – with more carbon than oxygen – could have exoplanets composed mostly of diamond, with some silica, if conditions are right. And now, in a lab, scientists have crushed and heated silicon carbide to find out what those conditions might be.
“These exoplanets are unlike anything in our solar system,”
The idea that stars with a higher carbon-oxygen ratio than the Sun could produce diamond planets first emerged with the discovery of 55 Cancri e, a super-terrestrial exoplanet orbiting a star believed to be rich. of carbon 41 light-years away.
It was later discovered that this star was not as rich in carbon as previously thought, which put an end to that idea, at least as far as 55 Cancri e is concerned.
But between 12 and 17 percent of planetary systems could be positioned around carbon-rich stars, and with thousands of stars hosting exoplanets identified to date, the diamond planet looks like a real possibility.
Scientists have already explored and confirmed the idea that such planets are likely composed primarily of carbides, carbon compounds and other elements. If such a planet were rich in silicon carbide, the researchers speculate, and if water was present to oxidize the silicon carbide and convert it to silicon and carbon, then with enough heat and pressure, the carbon could become diamond.
To confirm their hypothesis, they turned to a diamond anvil cell, a device used to squeeze small samples of material at very high pressures.
They took minute samples of silicon carbide and immersed them in water. Then, the samples were placed in the diamond anvil cell, which crushed them to pressures of up to 50 gigapascals, about half a million times the Earth’s atmospheric pressure at sea level. After the samples were squeezed, the team heated them with lasers.
In all, they ran 18 runs of the experiment and found that, just as they predicted, under high heat and high pressure, their silicon carbide samples reacted with water to convert to silica and diamond.
Therefore, the researchers concluded that at temperatures up to 2,500 Kelvin and pressures up to 50 gigapascals, in the presence of water, the silicon carbide planets could oxidize and have their internal compositions dominated by silica and diamond.
If we could identify these planets, perhaps based on their density profiles and the composition of their stars, we could then rule them out as planets that could host life.
Their interiors, the researchers said, would be too difficult for geological activity, and their composition would make their atmospheres inhospitable to life as we know it.
“This is one more step to help us understand and characterize our ever-increasing and improving observations of exoplanets,” Allen-Sutter said.
“The more we learn, the better we will be able to interpret new data from upcoming future missions such as the James Webb Space Telescope and the Nancy Grace Roman Space Telescope to understand the worlds beyond our Solar System.”
The research was published in The Planetary Science Journal.