As Webb begins observing exoplanets, scientists use Spitzer data & brown dwarfs to reveal how silicate clouds form

Date:
Mon, 18 Jul 2022 17:43:12 +0000

Description:
In a new study from a group of researchers in Canada, data from NASAs now-retired The post As Webb begins observing exoplanets, scientists use Spitzer data & brown dwarfs to reveal how silicate clouds form appeared first on NASASpaceFlight.com .

FULL STORY ======================================================================

In a new study from a group of researchers in Canada, data from NASAs now-retired Spitzer Space Telescope was used to determine the conditions
under which silicate clouds form on distant exoplanets outside of our solar system giving scientists insight into whats inside the atmospheres of exoplanets similar in size, temperature, and composition to Earth.

The study, led by Genaro Surez of Western University in London, Ontario, was released just weeks before the now-operational James Webb Space Telescopes first images were released on July 12. One of Webbs first images is spectral data of exoplanet WASP-96b, which, to the surprise of Webb teams, revealed clouds and haze inside the exoplanets atmosphere and gave scientists a small glimpse into what Webb can do when observing exoplanets.



Spitzer reveals how silicate clouds form

On Earth, were used to seeing clouds made of water molecules. However, on other planets and moons inside and outside our solar system, clouds come in many different chemical makeups.

On large gas giants, like Jupiter or Saturn, many clouds are made of ammonia and ammonium hydrosulfide, giving them (and their planets) a yellowish hue.
On planets similar to Mars, clouds can be made of both water vapor and carbon dioxide depending on atmospheric conditions. However, some exoplanets, or planets located outside of our solar system, have clouds composed of silicates, which are rock-forming minerals that comprise a large portion of Earths crust. This image, taken by NASAS Curiosity Mars rover, shows Martian clouds above a surface outcrop named Mont Mercou. (Credit: NASA/JPL-Caltech/ MSSS)

Up until the release of the Surez et al. study, scientists had little information on the conditions in which these silicate clouds form. However, using data from Spitzer, the researchers may now have an idea.

For the study, Surez et al. used observational data of brown dwarfs collected by Spitzer. Brown dwarfs are celestial bodies that are stuck in a state between a planet and a star, and though they form like stars, are not large enough to kick-start fusion within them. This gives brown dwarfs atmospheres that are extremely similar to gas giants, so these odd celestial bodies can
be used as a sort-of proxy for exoplanets with clouds.

See Also James Webb Telescope Images NSF Store L2 SpaceX Section Click here to Join L2

Understanding the atmospheres of brown dwarfs and planets where silicate clouds can form can also help us understand what we would see in the atmosphere of a planet thats closer in size and temperature to Earth, said co-author Stanimir Metchev, a professor of exoplanet studies at Western University in London, Ontario.

But first, how do rock-based silicate clouds form on exoplanets?

The cloud-forming process on exoplanets is actually very similar to how
clouds form on Earth and other terrestrial planets like Mars. The process starts with a key element or compound, such as water or ammonium, being
heated until it becomes a vapor. Then, after being trapped and cooled to a certain temperature, that element or compound will turn into a cloud.

On planets with silicate clouds, the planets surface or atmosphere would need to be extremely hot, as rock typically needs to be at a much higher temperature than other elements and compounds to vaporize into a gas. This means that these silicate clouds are only able to form on exoplanets that are extremely hot. Thankfully, brown dwarfs are failed stars and are extremely hot, which made them a great candidate for the Surez et al. study.



Spitzer data had already suggested the presence of silicate clouds in a few brown dwarf atmospheres years before the Surez et al. study began, back when Spitzer still operated with cryogenically cooled instruments during the first six years of its mission. However, the brown dwarf data that suggested the silicate clouds was extremely weak and wouldnt be able to confirm anything on the exoplanets confidently.

In order to confidently measure and investigate certain values and signatures in the Spitzer data, Surez et al. pulled over 100 Spitzer data sets that showed weak detections of silicate clouds in brown dwarf atmospheres and then grouped them based on the temperature of the brown dwarf observed. Fortunately, all 100+ data sets fell inside the predicted temperature range that silicate clouds should form which is between approximately 1,308 Celsius and 1,700 Celsius and revealed a trait of silicate clouds on brown dwarfs.

However, what happens if the exoplanet or brown dwarfs atmosphere is hotter than the top of the temperature range? What if its cooler than the bottom of the temperature range?

If the atmosphere of the brown dwarf or exoplanet is too hot and exceeds the top of the temperature range, the vapor from the melted rock will stay a
vapor and not condense into clouds. If the atmosphere temperature is cooler than the bottom-end of the temperature range, the clouds will sink lower in the atmosphere where the temperature is higher or they will begin to release precipitation.

We had to dig through the Spitzer data to find these brown dwarfs where there was some indication of silicate clouds, and we really didnt know what we
would find. We were very surprised at how strong the conclusion was once we had the right data to analyze, said Surez. In this illustration, each of the four brown dwarfs shown represents a different temperature. The far-left
brown dwarf is the warmest, with the far-right being the coldest, with the
two in the middle being inside the temperature range for silicate cloud formation. (Credit: NASA/JPL-Caltech)

Whats more, scientists currently believe that silicate clouds similar to
those investigated by Surez et al. exist deep inside Jupiters atmosphere. Jupiters atmospheric pressure significantly increases the deeper into its atmosphere you go, meaning temperatures likely significantly rise as well, melting rock and other minerals in Jupiter and turning them into silicate clouds. In fact, if Jupiters upper atmosphere were thousands of degrees hotter, the ammonia and ammonium hydrosulfide clouds currently present at the top of its atmosphere would vaporize and the deeper silicate clouds would likely rise to the top, replacing them.

As exoplanet-finding technology continues to advance, scientists are finding more and more unique exoplanet environments in our solar system. Many
recently discovered exoplanets are exhibiting strange and unique characteristics, like being tidally locked to their parent stars (which can cause various types of clouds to form depending on what side of the planet clouds are located). In order to understand why these distant worlds are exhibiting these strange characteristics, scientists first need to understand the basic geologic and physical functions that make them.

One major way scientists are planning to further their knowledge of
exoplanets is by using the new NASA/ESA/CSA James Webb Space Telescope, which recently just had its first images and data released. As aforementioned, one of these first images was of WASP-96b, an exoplanet located around star WASP-96 approximately 1.150 light-years from Earth. The spectral data
captured by Webb gives scientists a glimpse into the true power of Webb and what it can do when it comes to investigating and characterizing exoplanets. Webbs data on WASP-96b revealed clouds, haze, and a signature of water in its atmosphere all characteristics that were previously thought to not exist on WASP-96b. Unlike Spitzer, Webb has the power to image and determine elements in the atmospheres of exoplanets, allowing scientists to investigate these alien worlds in incredible detail that has never been possible.

Surez et al.s study was published in the Monthly Notices of the Royal Astronomical Society.

(Lead image: Artists depiction of the Spitzer Space Telescope. Credit: NASA/JPL-Caltech/R. Hurt (IPAC))

The post As Webb begins observing exoplanets, scientists use Spitzer data & brown dwarfs to reveal how silicate clouds form appeared first on NASASpaceFlight.com .



======================================================================
Link to news story: https://www.nasaspaceflight.com/2022/07/spitzer-brown-dwarfs-silicate-clouds/


--- Mystic BBS v1.12 A47 (Linux/64)
* Origin: tqwNet Science News (1337:1/100)