JWST detects quartz crystals in clouds of WASP-17 b
16 Oct 2023



Silica partciles detected on an exoplanet for the first time using MIRI.

​Artist’s concept of exoplanet WASP-17 b.

​Artist’s concept of exoplanet WASP-17 b

NASA, ESA, CSA, Ralf Crawford (STScI)

Researchers used the unique capabilities of MIRI to unveil evidence of quartz nanocrystals in the high-altitude clouds of WASP-17 b, a scorching hot Jupiter-like exoplanet located 1,300 light-years from Earth. This is the first instance of silica (SiO2) particles being observed in the atmosphere of an exoplanet.

Silicates, minerals rich in silicon and oxygen, are a key component of the Earth, the Moon, and other rocky objects in our solar system. However, previous observations of silicate grains in exoplanet atmospheres and brown dwarfs primarily revealed magnesium-rich silicates like olivine and pyroxene, rather than the pure SiO2 form of quartz.

WASP-17 b is a gas giant with a volume exceeding that of Jupiter over seven times but with a mass less than half that of Jupiter, is among the largest and most expansive exoplanets discovered. Its distinctive characteristics, coupled with an orbital period of just 3.7 Earth-days, make it an ideal subject for transmission spectroscopy – a technique that entails assessing how a planet's atmosphere influences starlight through filtering and scattering effects.

JWST observed Wasp-17 for nearly 10 hours. Comparing the brightness of specific wavelengths of light when the planet passed in front of its host star, the team utilized MIRI's capabilities to precisely determine the quantity of each wavelength blocked by the planet's atmosphere.

This discovery emphasises MIRI's e​xpertise in studying distant exoplanetary atmospheres.

Find out more.​