Researchers using Nasa’s James Webb Space Telescope have detected quartz crystals – the same material present on Earth’s Moon – in the clouds of a scorching exoplanet. Specifically, the team spotted silica (SiO2) particles in the high-altitude clouds of WASP-17 b, a hot Jupiter exoplanet located 1,300 light-years from Earth, using Webb’s MIRI (Mid-Infrared Instrument). This marks the first time such pure silica has been identified in an exoplanet atmosphere, and it raises new questions about how such minerals form in exoplanets.
WASP-17’s cloudy atmosphere – seven times more puffy than Jupiter’s – made it ideal for transmission spectroscopy. This technique allows scientists to measure how a planet’s atmosphere filters and reflects starlight as it passes through the star in front of it. For 10 hours, the team measured the brightness of mid-infrared light as the planet passed in front and behind its host star. By subtracting the brightness of each wavelength from the brightness of each when the planet was in front of the star alone, the team could calculate how much of each wavelength was blocked by the planet’s atmosphere. The astronomers found an unexpected “bump” at 8.6 microns, aligning with the absorption signature of pure quartz.
The findings are published in the Astrophysical Journal Letters. David Grant led the research from the University of Bristol, UK. In addition to Webb, Grant could also use data from the Hubble Space Telescope and previous observations from the ground-based U.K. Wide Field Imager.
Like Jupiter, WASP-17’s clouds are composed mainly of hydrogen and helium, with small amounts of carbon dioxide and water vapor. However, astronomers have yet to determine how much silica is present in the atmosphere and how widespread it is within the clouds. Moreover, they have yet to determine how large the crystals are.
In a future study, the team will combine Webb’s near-infrared and visible observations of the WASP-17 system with data from the upcoming Chandra X-ray Observatory to help constrain the size of the quartz particles. They will also look for evidence of other materials in the clouds, such as magnesium silicates, to understand how these other particles contribute to WASP-17’s atmospheric composition.
Webb is a powerful observatory that allows astronomers to study the most distant and exotic objects in our universe. Its observations will help uncover our solar system’s origin, the Milky Way, and the cosmic microwave background. It will also provide crucial information about extrasolar planets, including their temperatures, chemical makeup, and resulting atmospheres. Webb is being built by a team of more than 1,000 people at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. It is scheduled to launch in 2021. Goddard is home to many famous science missions, such as Hubble, the Voyager and Pioneer probes, and the Solar Dynamics Observatory. The partly wooded campus is 6.5 miles (10.5 km) northeast of Washington, D.C., in Prince George’s County.