ZB ZB
Live now
Start time
Playing for
End time
Listen live
Listen to NAME OF STATION
Up next
Listen live on
ZB

Quartz crystals detected swirling in an exoplanet’s atmosphere

Author
CNN,
Publish Date
Wed, 18 Oct 2023, 2:23PM
An artist's concept depicts what the exoplanet WASP-17b could look like. The hot gas giant has a thick, extended atmosphere, making it a "puffy" exoplanet. NASA, ESA, CSA, Ralf Crawford (STScI)
An artist's concept depicts what the exoplanet WASP-17b could look like. The hot gas giant has a thick, extended atmosphere, making it a "puffy" exoplanet. NASA, ESA, CSA, Ralf Crawford (STScI)

Quartz crystals detected swirling in an exoplanet’s atmosphere

Author
CNN,
Publish Date
Wed, 18 Oct 2023, 2:23PM

CNN — Astronomers using the James Webb Space Telescope have for the first time detected tiny quartz crystals containing silica — a common mineral on Earth — within the atmosphere of a blazing hot exoplanet.

It’s likely that the nanoparticles of silica, which on Earth appears in beach sands and is used to produce glass, swirl from the clouds of the exoplanet, known as WASP-17b, according to the researchers.

First discovered in 2009, WASP-17b is a gas giant planet located 1,300 light-years from Earth. It has a volume more than seven times that of Jupiter, making it one of the largest exoplanets known to astronomers.

This artist's concept shows what the exoplanet WASP-17 b could look like.

WASP-17 b, also called Ditsö̀, is a hot gas giant that orbits its star at a distance of just 0.051 AU (about 4.75 million miles, or one-eighth the distance between Mercury and the Sun), completing one full circuit in about 3.7 Earth-days. The system lies within the Milky Way, about 1,300 light-years from Earth, in the constellation Scorpius.

With a volume more than seven times that of Jupiter and a mass less than one-half of Jupiter, WASP-17 b is an extremely puffy planet. Its short orbital period, large size, and thick, extended atmosphere make it ideal for observation using transmission spectroscopy, which involves measuring the effects of the planet's atmosphere on the starlight filtering through it.

WASP-17 b's atmosphere is composed primarily of hydrogen and helium, along with small amounts of water vapor and hints of carbon dioxide and other molecules. Observations of 5- to 12-micron infrared light from Webb's MIRI (Mid-Infrared Instrument) show that WASP-17 b's atmosphere also contains clouds made of nanocrystals of quartz (SiO2).

WASP-17 b is tidally locked and has a retrograde orbit. Its temperature ranges from about 1,000 kelvins (1,350 degrees F or 725 degrees C) on the cooler nightside to nearly 2,000 kelvins (3,150 degrees F or 1,725 degrees C) on the side in permanent daylight.

The star, WASP-17 (also called Diwö), is an F-type star: slightly larger, more massive, hotter, and whiter than the Sun.

This artist's concept is based on new data gathered by MIRI as well as previous observations from other ground- and space-based telescopes, including NASA's Hubble and retired Spitzer space telescopes. Webb has not captured any images of the planet.

An artist's concept depicts what the exoplanet WASP-17b could look like. The hot gas giant has a thick, extended atmosphere, making it a "puffy" exoplanet. NASA, ESA, CSA, Ralf Crawford (STScI)

The researchers detected the the quartz nanoparticles in high-altitude clouds using Webb’s Mid-Infrared Instrument, according to new research published Monday in The Astrophysical Journal Letters.

“We were thrilled,” said lead study author David Grant, a researcher at the University of Bristol, in a statement. “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.”

Minerals rich in silicon and oxygen, called silicates, are plentiful on Earth, the moon and other rocky bodies in the solar system. Silicates are also incredibly common in the Milky Way galaxy. But so far, the silicate grains detected in exoplanet atmospheres have been magnesium-based, not quartz, which is made of pure silica.

 “We fully expected to see magnesium silicates,” said study coauthor Hannah Wakeford, senior lecturer in astrophysics at University of Bristol, in a statement.
“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.”

The finding could enable researchers to understand the materials used to form planetary environments much different from what we know on Earth.

What the quartz crystals reveal about WASP-17b

Wasp-17b takes 3.7 Earth days to complete one orbit around its star. Astronomers focused their observations on the exoplanet as it crossed in front of its star and starlight filtered through its atmosphere.

After 10 hours of observation time, the team discovered a signature suggesting the presence of quartz nanoparticles.

The quartz crystals are likely hexagonal in shape, like the much larger geodes we know on Earth, but each one is only one-millionth of a centimeter — so small that 10,000 of the grains could fit side by side across a human hair, according to the research. And the particles originate in the atmosphere.

A transmission spectrum of the hot gas giant exoplanet WASP-17 b captured by MIRI (Webb's Mid-Infrared Instrument) on March 12-13, 2023, reveals the first evidence for quartz (crystalline silica, SiO2) in the clouds of an exoplanet.

The spectrum was made by measuring the change in brightness of 28 wavelength-bands of mid-infrared light as the planet transited its star. Webb observed the WASP-17 system using MIRI's low-resolution spectrograph for nearly 10 hours, collecting more than 1,275 measurements before, during, and after the transit.

For each wavelength, the amount of light blocked by the planet's atmosphere (white circles) was calculated by subtracting the amount that made it through the atmosphere from the amount originally emitted by the star.

The solid purple line is a best-fit model to the Webb (MIRI), Hubble, and Spitzer data. (The Hubble and Spitzer data cover wavelengths from 0.34 to 4.5 microns and are not shown on the graph.) The spectrum shows a clear feature around 8.6 microns, which astronomers think is caused by silica particles absorbing some of the starlight passing through the atmosphere.  

The dashed yellow line shows what that part of the transmission spectrum would look like if the clouds in WASP-17 b's atmosphere did not contain SiO2.

This marks the first time that SiO2 has been identified in an exoplanet, and the first time any specific cloud species has been identified in a transiting exoplanet.

Webb detected quartz crystals in the atmosphere of WASP-17b. NASA, ESA, CSA, Ralf Crawford (STScI)

“WASP-17 b is extremely hot — around 2,700 degrees Fahrenheit (1,500 degrees Celsius) — and the pressure where the quartz crystals form high in the atmosphere is only about one-thousandth of what we experience on Earth’s surface,” Grant said. “In these conditions, solid crystals can form directly from gas, without going through a liquid phase first.”

The planet is tidally locked to its star, meaning one side always faces the star and experiences searing temperatures, while the permanent “night” side of the planet is cooler. While the clouds can drift around the planet, they likely vaporize on the hot day side, which could send the quartz particles swirling.

“The winds could be moving these tiny glassy particles around at thousands of miles per hour,” Grant said.

Webb’s sensitive detections are allowing researchers to have a better understanding of the atmospheres, environmental conditions and weather on planets outside of our solar system.

Hot gas giants, also called Hot Jupiters, like WASP-17b are largely composed of hydrogen and helium, along with some water vapor and carbon dioxide. Detecting silica in the planet’s atmosphere helps scientists to have a broader sense of WASP-17b’s composition.

“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,” Wakeford said. “These beautiful silica crystals tell us about the inventory of different materials and how they all come together to shape the environment of this planet.”

Take your Radio, Podcasts and Music with you