December 11, 2023


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Silica ice envelops the fiery atmosphere of hot exoplanet Jupiter

Silica ice envelops the fiery atmosphere of hot exoplanet Jupiter

This artist’s concept shows what the exoplanet WASP-17 b could look like. WASP-17 b, also known as 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 is located within the Milky Way Galaxy, about 1,300 light-years from Earth, in the constellation Scorpius. With a volume more than seven times the size of Jupiter and a mass less than half that of Jupiter, WASP-17 b is an extremely bloated planet. Its short orbital period, large size, and thick, expansive atmosphere make it ideal for observation using transmission spectroscopy, which involves measuring the effects of a planet’s atmosphere on the starlight filtering through it. Image credit: NASA, ESA, CSA, Ralph Crawford (STScI)

Flakes of silica “snow” fill the sky of the superheated, puffy exoplanet WASP-17 b.

A look at one of the most common and familiar minerals on Earth rarely deserves a headline. Quartz is found in beach sand, building stones, geodes, and gem shops around the world. It is melted to produce glass, refined for silicon microchips, and used in watches to keep time.

So what distinguishes the latest discovery from? NASA‘s James Webb Space Telescope? Imagine quartz crystals literally appearing out of thin air. A mist of shimmering grains so small that 10,000 of them could fit side by side across a human hair. Swarms of pointy glass nanoparticles race through the hot atmosphere of a puffy gas giant Exoplanet At thousands of miles per hour.

Webb’s unique ability to measure the extremely subtle effects of those crystals on starlight — and from a distance of more than seven million billion miles, at least — provides important information about the composition of exoplanetary atmospheres and new insights into their weather.

Exoplanet WASP-17 b (Webb MIRI transmission spectrum)

The transmission spectrum of the hot gas giant exoplanet WASP-17 b, captured by MIRI (Webb Mid-Infrared Instrument) on March 12-13, 2023, reveals the first evidence of quartz (crystalline silica, SiO2) in the exoplanet’s clouds. Solar.
The spectrum was made by measuring the change in brightness of 28 wavelength bands of mid-infrared light as the planet passes its star. Webb observed the WASP-17 system using a low-resolution MIRI spectrometer for about 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 passed through the atmosphere from the amount originally emitted by the star.
The solid purple line is the model best fit 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 in the graph.) The spectrum shows a clear feature at about 8.6 microns, which astronomers believe is caused by silica particles absorbing some of the starlight passing through the atmosphere.
The yellow dashed line shows what this part of the transmission spectrum would look like if the clouds in the atmosphere of WASP-17 b did not contain SiO2.
This is the first time SiO2 has been identified in an exoplanet, and the first time any specific type of cloud has been identified in a passing exoplanet.
Image credit: NASA, ESA, CSA, Ralph Crawford (STScI), David Grant (University of Bristol), Hannah R. Wakeford (University of Bristol), Nicole Lewis (Cornell University)

The Webb Space Telescope detects tiny quartz crystals in giant hot gas clouds

Researchers using NASA’s James Webb Space Telescope have discovered evidence of quartz nanocrystals in the high-altitude clouds of WASP-17 b, a hot planet. Jupiter An exoplanet 1,300 light-years from Earth. This discovery, which was uniquely possible using MIRI (Webb’s mid-infrared instrument), represents the first time silica (SiO) has been detected.2) Particles have been detected in the atmosphere of an exoplanet.

“We were thrilled!” David Grant, a researcher at… University of Bristol In the UK and first author of a paper published today (October 16) in Astrophysical Journal Letters. “We knew from Hubble observations that aerosols — small particles that form clouds or fog — must be present in the atmosphere of WASP-17 b, but we did not expect them to be made of quartz.”

Silicates (minerals rich in silicon and oxygen) make up the bulk of the Earth and Moon as well as other rocky bodies in our solar system, and are extremely common throughout the galaxy. But silicate grains previously detected in the atmospheres of exoplanets and brown dwarfs appear to be made of magnesium-rich silicates such as olivine and pyroxene, not quartz alone – which is pure SiO.2.

The finding by this team, which also includes researchers from NASA Ames Research Center and NASA Goddard Space Flight Center, puts a new spin on our understanding of how exoplanetary clouds form and evolve. “We were fully expecting to see magnesium silicate,” said co-author Hannah Wakeford, also from the University of Bristol. “But what we see instead are likely the building blocks of those particles, the tiny ‘seed’ particles needed to form the larger silicate grains we detect in cold exoplanets and brown dwarfs.”

Discover the subtle differences

With a volume more than seven times the size of Jupiter and a mass less than half that of Jupiter, WASP-17 b is one of the largest and most bloated exoplanets known. This, combined with its short orbital period of just 3.7 Earth days, makes the planet ideal for transmission spectroscopy: a technique that involves measuring the filtering and scattering effects of a planet’s atmosphere on starlight.

Webb monitored the WASP-17 system for about 10 hours, collecting more than 1,275 measurements of the brightness of 5- to 12-micron mid-infrared light as the planet transited its star. By subtracting the brightness of the individual wavelengths of light that reached the telescope when the planet was in front of the star from that of the star alone, the team was able to calculate how much of each wavelength was blocked by the planet’s atmosphere.

What emerged was an unexpected “bump” at 8.6 microns, a feature that would not have been expected if the clouds were made of magnesium silicate or other potentially high-temperature aerosols such as aluminum oxide, but makes perfect sense if they were made of quartz.

Crystals, clouds and wind

While these crystals may be similar in shape to the pointed hexagonal prisms found in geodes and gem shops on Earth, each one is only about 10 nanometers across — a millionth of a centimeter.

“The Hubble data actually played a key role in determining the size of these particles,” explained co-author Nicole Lewis from Cornell University, who leads the Guaranteed Time Observation (GTO) Web program designed to help build a 3D view of hot planets. Jupiter’s atmosphere. “We know about the presence of silica from Webb’s MIRI data alone, but we needed visible and near-infrared observations from Hubble for context, to know how big the crystals are.”

Unlike mineral particles found in clouds on Earth, the quartz crystals detected in WASP-17 b’s clouds were not recovered from a rocky surface. Instead, they originate in the atmosphere itself. “WASP-17 b is extremely hot – about 2,700 degrees F (1500 degrees Celsius) – The pressure where quartz crystals form high in the atmosphere does not exceed about one thousandth of what we experience on the surface of the Earth. “Under these conditions, solid crystals can form directly from the gas, without going through a liquid phase first.”

Understanding the components of clouds is crucial to understanding the planet as a whole. Hot Jupiters like WASP-17 b are composed primarily of hydrogen and helium, with small amounts of other gases such as water vapor (H).2O) and carbon dioxide (CO2). “If we only consider the oxygen contained in these gases, and neglect to include all the oxygen trapped in minerals such as quartz (SiO),2We will dramatically reduce overall abundance,” Wakeford explained. “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.”

It is difficult to determine exactly how much quartz is present, and how widespread the clouds are. “The clouds are likely to be present along the transition between day and night (the separator), which is the area our observations are exploring,” Grant said. Because the planet is tidally locked with a very hot dayside and a cooler nightside, clouds likely orbit the planet, but evaporate when they reach the hotter dayside. “The wind can move these tiny glass particles at thousands of miles per hour.”

WASP-17 b is one of three planets targeted by the JWST team of scientists for Deep Reconnaissance of Exoplanetary Atmospheres using Resolution Multi-Instrument Spectroscopy (DREAMS) probes, which are designed to collect a comprehensive set of observations of a single representative from each major class of exoplanets. : Jupiter is hot, warm NeptuneAnd a moderate rocky planet. MIRI observations of the hot Jupiter WASP-17 b were made as part of the GTO 1353 program.

Reference: “JWST-TST Dreams: Quartz Clouds in the Atmosphere of WASP-17b” by David Grant, Nicole K. Lewis, Hannah R. Wakeford, Natasha E. Batalha, Anna Glidden, Jayesh Goyal, Elijah Mullins, Ryan J. MacDonald, Erin M. May, Sarah Seager, Kevin B. Stevenson, Jeff A. Valenti, Channon Fisher, Lily Alderson, Natalie H. Allen, Caleb I. Cañas, Kencol Colon, Mark Clampin, Nestor Espinoza, Amelie Gresier, Jingsheng Huang, Zifan Lin, Douglas Long, Dana R. Lowe, Maria Peña Guerrero, Sukrit Rangan, Christine S. Sotzen, Daniel Valentine, Jay Anderson, William O. Palmer, Andrea Bellini, Kellan K. W. Hoch, Jens Kammerer, Mattia Liberalto, C. Matt Mountain, Marshall de Perrin, Laurent Boyot, Emily Rickman, Isabel Rebolledo, Sangmo Tony Son, Roland P. van der Marel, and Laura L. Watkins, October 16, 2023, Astrophysical Journal Letters.
doi: 10.3847/2041-8213/acfc3b

The James Webb Space Telescope is the world’s leading space science observatory. Webb solves the mysteries of our solar system, looks beyond the distant worlds around other stars, and explores the mysterious structures and origins of our universe and our place in it. WEB is an international program led by NASA with its partners the European Space Agency (ESA).European Space Agency) and the Canadian Space Agency.

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