Far From Earth, a Gigantic Planet Lies Cloaked in Clouds of Pure Quartz

Around 1,300 light-years away from Earth there’s a steamy, hot, massive exoplanet covered in clouds. But unlike Earth's watery haze, this planet is the first ever found where the clouds are made up of tiny crystals of quartz.  

The discovery is described in a new paper in the Astrophysical Journal Letters. In the paper, the researchers explain how NASA's James Webb Space Telescope revealed the strange weather on WASP-17b, which is a "hot Jupiter," a gas giant planet similar to our solar system's own Jupiter in that it is made up of gas but which sits extremely close to its host star, making it much hotter. (WASP-17b is also much puffier than Jupiter, as it is seven times the size but only half the mass of our planet neighbor.)

Past observations of WASP-17b had found aerosols — that is, tiny particles that make up a misty haze — around the planet, what those particles were made of was a mystery — until now.

And while materials known as silicates, a type of salt which contains both silicon and oxygen, are very common in the atmospheres of planets and other celestial bodies, pure silicate, or quartz, is much rarer. 

"We fully expected to see magnesium silicates," co-author Hannah Wakeford, who teaches astrophysics at the University of Bristol, said in a NASA statement. "But what we’re seeing instead are likely the building blocks of those, the tiny 'seed' particles needed to form the larger silicate grains we detect in cooler exoplanets and brown dwarfs."

The researchers observed WASP-17b for just under 10 hours, measuring its light more than 1,200 times. Because it’s orbit is so short — a year, or rotation around its star, takes just under four Earth days — the team was able to analyze the light coming from the exoplanet when it was in front of and behind its star. By analyzing the wavelengths of light, the team could infer the elements and molecules in the planet's atmosphere.

What they found are signs of clouds of tiny quartz crystals, one-millionth of a centimeter in diameter. The researchers believe the quartz forms in the atmosphere itself: because the heat on WASP-17b is so intense, and the pressure in the atmosphere so low, the solid crystals are able to form directly from a gas, without ever passing through a liquid stage. 

It is unclear just how much quartz exists on the exoplanet, but what is clear is that the planet is tumultuous. Because the days are so short and hot, and the nights relatively cool, scientists believe the quartz clouds must circulate around the planet, carried on winds that can reach thousands of miles per hour.