Webb Discovers Quartz Crystals In Clouds Of A Giant Gas Planet And NASA Is Stunned

hero webb artist rendition wasp 17 b
NASA's James Webb Space Telescope (JWST) detected evidence of quartz nanocrystals in a Jupiter-like exoplanet's atmosphere 1,300 light-years from Earth. The first-ever detection of silica particles in an exoplanet's atmosphere was made possible by Webb's Mid-Infrared Instrument (MIRI).

WASP-17 b, also known as Ditso, is a hot gas giant that lies within the Milky Way in the constellation Scorpius. Its short orbital period, large size, and thick, extended atmosphere make it an ideal candidate for observation using transmission spectroscopy, which consists of measuring the effects of the planet's atmosphere on the starlight filtering through it.

Webb observed the WASP-17 system for about 10 hours, collecting more than 1,275 brightness measurements of 5- to 12-micron mid-infrared light as the planet crossed its star. It was through this observation the team was able to detect the presence of silica particles in the WASP-17 b's atmosphere.

"We are thrilled!" exclaimed David Grant, a researcher at the University of Bristol in the UK and first author on a new paper about the discovery. "We knew from Hubble observations that there must be aerosols, tiny particles making up clouds or haze, in WASP-17 b's atmosphere, but we didn't expect them to be made of quartz."

graph of composition cloud particles
A transmission spectrum of the hot gas giant exoplanet WASP-17 b.

The team members said they fully expected to see magnesium silicates, but what they saw instead were likely the building blocks of those, "the tiny 'seed' particles needed to form the larger silicate grains" they detected in cooler exoplanets and brown dwarfs.

"Hubble data actually played a key role in constraining the size of these particles," explained co-author Nikole Lewis of Cornell University. "We know there is silica from Webb's MIRI data alone, but we needed the visible and near-infrared observations from Hubble for context, to figure out how large the crystals are."

The team says that understanding what the clouds are made of is critical for understanding the planet as a whole.

"If we only consider the oxygen that is in these gases, and neglect to include all of the oxygen locked up in minerals like quartz, we will significantly underestimate the total abundance," remarked co-author Hannah Wakeford from the University of Bristol. "These beautiful silica crystals tell us about the inventory of different materials and how they all come together to shape the environment."

WASP-17 b is only one of three exoplanets targeted by the JWST-Telescope Scientist Team's Deep Reconnaissance of Exoplanet Atmospheres using Multi-instrument Spectroscopy (DREAMS) investigations. It is designed to gather a comprehensive set of observations of one representative from each key class of exoplanets: a hot Jupiter, a warm Neptune, and a temperate rocky planet.