Webb detects sand clouds for a brown dwarf

See bigger. | Another 1st! Webb detects sand clouds in a brown dwarf atmosphere! This artist’s impression depicts a brown dwarf, an object more massive than the largest planets in our solar system, but not massive enough to ignite and shine like a star. Image via NOIRLab/ NSF/ AURA/ P. Marenfeld/ William Pendrill.

Another 1st for Webb

The James Webb Space Telescope has directly detected sand clouds in the atmosphere of one of the star-planet hybrids known as a brown dwarf. These thick clouds are not made up of water vapor like clouds on Earth. Instead, they are composed of tiny silicate particles. Scientists had hypothesized the existence of sand clouds for exoplanets. But Webb’s new sightings – reported September 5, 2022 by Scientific alert – are the first verified discovery.

The research team has submitted a paper of their findings to AAS journals (not yet peer-reviewed).

This new discovery marks another first for the space telescope, which is located about four times the distance from the Moon to Earth.

Earlier this month NASA announced that Webb had taken his first image of an exoplanet orbiting a distant star. A few days earlier, Webb scientists said they had detected carbon dioxide in the atmosphere of another exoplanet, the first-ever confirmed discovery of the gas on another world outside our solar system.

Webb detects clouds of sand

Brown dwarfs are objects in space whose masses fall between those of giant planets – like Saturn and Jupiter – and the smallest stars. Webb’s new discovery involves a brown dwarf called VHS 1256-1257 b. It is 72 light years from Earth and about 19 times more massive than Jupiter. Astronomer Brittany Miles of the University of California, Santa Cruz and her colleagues from the James Webb Space Telescope (JWST) team found evidence of sand clouds in Webb Telescope data.

Sand clouds are composed of silicate mineral particles. These particles are most likely forsterite, enstatite or quartz, according to the team’s scientists. They are also likely submicron (less than a micron) in size, like particles in smoke or smog.

Scientists have speculated that such clouds could exist on brown dwarfs or exoplanets, but this is the first time they have been directly detected. Paper:

The spectral shape of VHS 1256 b is influenced by the chemistry of imbalance and clouds. We are directly detecting silicate clouds, the first such detection reported for a planetary-mass companion.

Silicate clouds – aka sand clouds – can only form on hot worlds. Indeed, silicates require very high temperatures to vaporize. You need atmospheric temperatures between about 1000 degrees C (1832 degrees F) and 1700 C (3092 F). But in atmospheres warmer than the upper end of this range, the silicates remain in vapor form.

3 planets on the left, 2 brown dwarfs in the middle and 1 bright star on the right, on a black background with white text.
See bigger. | Brown dwarfs fall between planets and stars in terms of mass. Image via NASA/JPL-Caltech.

The Webb telescope, a “pioneer”

The researchers found that the atmosphere of VHS 1256-1257 b is quite complex. In addition to silicate clouds, Webb also detected several other gases and elements. As the log puts it:

Water, methane, carbon monoxide, carbon dioxide, sodium and potassium are observed in several parts of the JWST spectrum based on model comparisons of brown dwarf spectra, molecular opacities and models atmospheric.

As mentioned earlier, Webb has also detected carbon dioxide on another exoplanet, making it the second world outside our solar system where Webb has found evidence of CO2.

Webb’s new brown dwarf observations will be invaluable for future observations of other brown dwarfs. As the researchers stated in the article:

These first results of the [Webb] The first published scientific observations are groundbreaking and can also be obtained for many other nearby brown dwarfs that will be observed in future observing cycles. This observatory [the Webb telescope] will be a pioneer, pushing our understanding of atmospheric physics in planetary companions, brown dwarfs and exoplanets for years to come.

4 spheres ranging from bright yellow to dark red, from left to right.  Mottled appearance on the last 3.
See bigger. | Artist’s concept of 4 brown dwarfs, from hottest to coldest, left to right. Both medium brown dwarfs have temperature ranges conducive to the formation of silicate clouds: essentially sand clouds. Image via NASA/JPL-Caltech.

Learn more about brown dwarfs

Brown dwarfs are unusual objects, halfway between the biggest planets and the smallest stars. They are more massive than planets like Jupiter, but not massive enough for hydrogen fusion to ignite in their cores. This leaves them in a state of uncertainty where they are not massive enough to become true stars. However, they still emit their own heat and light, unlike planets. They are generally defined as a body between more than 13 and less than 80 Jupiter masses.

Some brown dwarfs orbit stars or other brown dwarfs, others travel alone in the galaxy.

Conclusion: NASA’s Webb Telescope discovered sand clouds in the atmosphere of a brown dwarf 72 light years away. The existence of such clouds has long been assumed to exist, but has not been confirmed so far.

Source: JWST Early Release Science Program for Direct Observation of Exoplanetary Systems II: A 1-20 Micron Spectrum of Planetary Mass Companion VHS 1256-1257b

Via Science Alert

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