In a groundbreaking discovery, researchers using NASA’s James Webb Space Telescope have identified evidence for quartz nanocrystals in the high-altitude clouds of WASP-17 b, a hot Jupiter exoplanet located 1,300 light-years away from Earth. The detection of these silica particles (SiO2) in an exoplanet atmosphere is a first and was made possible by the telescope’s Mid-Infrared Instrument (MIRI).
The research team, which includes scientists from the University of Bristol, NASA’s Ames Research Center, and NASA’s Goddard Space Flight Center, made the unexpected finding while studying the atmosphere of WASP-17 b. Previous observations with the Hubble Space Telescope indicated the presence of aerosols, tiny particles that form clouds or haze, but the composition was unknown until now.
“We were thrilled!” said David Grant, a researcher at the University of Bristol and the first author of the study published in the Astrophysical Journal Letters. “We knew from Hubble observations that there must be aerosols in WASP-17 b’s atmosphere, but we didn’t expect them to be made of quartz.”
Silicates, minerals rich in silicon and oxygen, are common in our solar system and across the galaxy. However, the silicate grains previously detected in exoplanet atmospheres were magnesium-rich silicates like olivine and pyroxene, not pure quartz (SiO2).
The discovery of quartz nanocrystals in the atmosphere of WASP-17 b challenges current understanding of how exoplanet clouds form and evolve. Hannah Wakeford, a co-author from the University of Bristol, explained, “We fully expected to see magnesium silicates, 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.”
WASP-17 b, with a volume more than seven times that of Jupiter and a mass less than half of Jupiter’s, is one of the largest known exoplanets. Its short orbital period of just 3.7 Earth-days makes it an ideal target for transmission spectroscopy, a technique used to study the composition of exoplanet atmospheres.
During nearly 10 hours of observation, the James Webb Space Telescope collected over 1,275 measurements of mid-infrared light as the planet crossed in front of its star. By analyzing the wavelengths of light blocked by the planet’s atmosphere, the researchers identified an unexpected “bump” at 8.6 microns, a feature consistent with the presence of quartz.
This groundbreaking discovery provides new insights into the composition and formation of exoplanet clouds. The detection of silica particles in the atmosphere of WASP-17 b opens up possibilities for further exploration of exoplanets and a deeper understanding of their atmospheres.
The James Webb Space Telescope continues to push the boundaries of exoplanet research, and scientists anticipate even more exciting discoveries as its mission progresses.
