Researchers using NASA’s James Webb Space Telescope have made a groundbreaking discovery by detecting evidence of quartz nanocrystals in the high-altitude clouds of WASP-17 b, a distant hot Jupiter exoplanet located 1,300 light-years away from Earth. This discovery, made possible by Webb’s MIRI (Mid-Infrared Instrument), marks the first-ever detection of silica (SiO2) particles within an exoplanet’s atmosphere.
A Surprising Find
David Grant, a researcher from the University of Bristol and the lead author of a study published in the Astrophysical Journal Letters, expressed his excitement about the discovery. The team had expected to find aerosols in the atmosphere of WASP-17 b, but they were astonished to discover that these tiny cloud particles were made of quartz.
Reevaluating Exoplanet Cloud Formation
Silicates, which are minerals rich in silicon and oxygen, are common in our solar system and across the galaxy. However, prior to this discovery, silicate grains identified in exoplanet atmospheres were predominantly magnesium-rich, such as olivine and pyroxene, not pure quartz (SiO2). This result challenges and broadens our understanding of how clouds form and evolve on exoplanets.
Unique Characteristics of WASP-17 b
WASP-17 b, with a volume more than seven times that of Jupiter and a mass less than half of Jupiter, is one of the largest and most voluminous exoplanets known. Its short orbital period of 3.7 Earth days and substantial size make it an ideal candidate for transmission spectroscopy, a technique used to study an exoplanet’s atmosphere by observing the effects of starlight as it passes through. The observations of WASP-17 b were conducted over almost 10 hours, collecting a substantial dataset of mid-infrared light.
Evidence for Quartz Crystals
The research team detected an unexpected “bump” in the data at 8.6 microns. This feature was not consistent with the presence of magnesium silicates or other high-temperature aerosols like aluminum oxide, but it aligned perfectly with the presence of quartz crystals.
Crystals, Clouds, and Winds
These quartz crystals, though similar in shape to those found on Earth, are incredibly tiny, measuring only about 10 nanometers in diameter. They originate within the planet’s atmosphere itself due to the unique conditions of WASP-17 b, which is extremely hot and experiences low atmospheric pressure. Here, solid crystals can form directly from gas without transitioning through a liquid phase.
Implications for Understanding Exoplanets
The discovery of quartz in the clouds of WASP-17 b sheds light on the composition of exoplanets and the materials that shape their environments. This knowledge is essential for understanding the planet as a whole. The presence of quartz implies a more complex atmospheric composition than previously thought.
Challenges in Quantification
Determining the exact quantity of quartz and the extent of the clouds on WASP-17 b is challenging. These clouds are likely present around the day/night transition (terminator), which was the focus of the observations. Given the extreme temperature differences between the day and night sides of the planet, the clouds likely circulate and disperse rapidly.
DREAMS Investigations
WASP-17 b is one of the three planets targeted for study by the JWST Telescope Scientist Team’s Deep Reconnaissance of Exoplanet Atmospheres using Multi-instrument Spectroscopy (DREAMS) investigations. These investigations aim to gather comprehensive observations of key exoplanet classes, including hot Jupiters, warm Neptunes, and temperate rocky planets.
About the James Webb Space Telescope
The James Webb Space Telescope is a cutting-edge space observatory tasked with exploring our solar system, distant worlds around other stars, and the origins of our universe. It is an international collaboration led by NASA in partnership with ESA (European Space Agency) and the Canadian Space Agency.
The MIRI (Mid-Infrared Instrument) on Webb was developed through a joint effort between NASA and ESA, with JPL (NASA’s Jet Propulsion Laboratory) leading the U.S. contributions. A multinational consortium of European astronomical institutes contributes on behalf of ESA. George Rieke from the University of Arizona leads the MIRI science team, and Gillian Wright is the MIRI European principal investigator. The development of the MIRI cryocooler was a collaboration between JPL, Northrop Grumman, and NASA’s Goddard Space Flight Center.
