Using JWST, scientists observe silicate clouds and measure the temperature of exoplanets

Date:
Mon, 03 Apr 2023 19:00:10 +0000

Description:
With help from the joint NASA/ESA/CSA James Webb Space Telescope, two teams
of scientists have The post Using JWST, scientists observe silicate clouds
and measure the temperature of exoplanets appeared first on NASASpaceFlight.com .

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

With help from the joint NASA/ESA/CSA James Webb Space Telescope, two teams
of scientists have made groundbreaking, first-of-their-kind discoveries on
two exoplanets. One team utilized the immense power of Webbs Mid-Infrared Instrument (MIRI) and Near-Infrared Spectrograph (NIRSpec) instruments to observe and characterize clouds and molecules in the atmosphere of an exoplanet located 40 light-years away.

The second team of scientists also utilized MIRI to measure the temperature
of a rocky exoplanet in the TRAPPIST-1 star system, located around 40 light-years away from Earth. The teams determined the temperature by
measuring the infrared light emitted by the planet the first time any light emitted by a rocky exoplanet has been detected and measured by a telescope.



Webb Characterizes Clouds and Molecules in Exoplanets Atmosphere

Throughout the last few decades, scientists have continued to learn more and more about the atmospheres of exoplanets scattered throughout the Milky Way. Using telescopes like Hubble and NASAs Transiting Exoplanet Survey Satellite (TESS), scientists could characterize the atmospheres of exoplanets for several years. However, scientists typically have to identify one atmospheric feature at a time until now.

Webbs latest exoplanet observations continue to display the true power of the infrared telescope, as teams were able to extract the data for multiple atmospheric features from a single observation of the exoplanet by Webb. No other telescope identified as many exoplanetary features in a single observation as Webb did in this one observation of the exoplanet. Artists illustration of VHS 1256b, with swirling silicate clouds seen in the planets upper atmosphere. (Credit: NASA/ESA/CSA/Joseph Olmsted (STScI))

The exoplanet, named VHS 1256b, is located around 40 light-years away from Earth around a tightly-locked binary star system. With an orbital period of approximately 10,000 years, the planet orbits its host stars at a distance that is around four times the distance between Pluto and our Sun. This made VHS 1256b a fantastic target for Webb, as the light emitted by the exoplanet wouldnt be mixed in with the light emitted by its host stars meaning a coronagraph or the commonly-used transit method wouldnt be needed when collecting data on the exoplanet. See Also JWST Mission Updates Space Science coverage L2 Future Spacecraft Click here to Join L2

Although its orbital distance and period are nothing short of extreme, its rotational period is fairly normal, completing a single rotation in 22 hours. VHS 1256bs strange characteristics continue to impress, though, as each time the planet completes a single rotation, its thick atmosphere rises, mixes,
and moves dramatically so much so that VHS 1256bs intense brightness
changes, caused by its ever-changing atmosphere, make it the most variable planetary-mass object ever discovered. Swirling in the upper atmosphere of
the exoplanet are silicate clouds, which churn in scorching atmospheric temperatures as high as 830 degrees Celsius.

Whats more, Webbs data also indicated the presence of water, methane, carbon monoxide, and carbon dioxide. Led by Brittany Miles of the University of Arizona, the teams observations represent the most molecules ever detected in an exoplanetary atmosphere from a single observation.

The silicate clouds in VHS 1256bs atmosphere can remain at high altitudes due to the planets low gravity unlike many other brown dwarf exoplanets, which have stronger gravitational forces. Webb was able to collect data on the clouds because of their high atmospheric altitude, and the data showed both large and small silicate particles in these silicate clouds, which can be
seen on a spectrum created by Webbs NIRSpec and MIRI instruments. The
emission spectrum of VHS 1256b, measured by the James Webb Space Telescope. (Credit: NASA/ESA/CSA/J. Olmsted (STScI)/Brittany Miles (University of Arizona)/Sasha Hinkley (University of Exeter)/Beth Biller (University of Edinburgh)/Andrew Skemer (University of California, Santa Cruz))

Were seeing a lot of molecules in a single spectrum from Webb that detail the planets dynamic cloud and weather systems, said Miles.

The finer silicate grains in its atmosphere may be more like tiny particles
in smoke. The larger grains might be more like very hot, very small sand particles, said co-author Beth Biller of the University of Edinburgh in Scotland.

In addition to the high-altitude silicate clouds, VHS 1256bs tumultuous atmosphere may be caused by the planets age. At only 150 million years old, VHS 1256b is quite young in astronomical terms, meaning it is likely still in the later stages of its formation and has not yet begun to cool to normal planetary temperatures.

However, though these findings are groundbreaking, theyre just the initial findings from Miles et al. As the team continues to comb through the data, theyll likely find more elements or structures in the atmosphere of the exoplanet. Furthermore, the data has been pulled from only a single observation of the exoplanet. Future observations of VHS 1256b could reveal even more about its volatile atmosphere and extreme characteristics.

Weve identified silicates, but better understanding which grain sizes and shapes match specific types of clouds is going to take a lot of additional work. This is not the final word on this planet it is the beginning of a large-scale modeling effort to fit Webbs complex data, Miles said.

Theres a huge return on a very modest amount of telescope time. With only a few hours of observations, we have what feels like unending potential for additional discoveries, Biller added. Sandcoarse, rough, gets everywhere. We may have found it on VHS 1256 b, a Tatooine-like world orbiting twin suns. Among other molecules, Webb detected silicate dust grains in its atmosphere. The larger grains may be like very hot, small sand particles: https://t.co/cl0jPDVYST pic.twitter.com/nwgMPpXFH4

NASA Webb Telescope (@NASAWebb) March 22, 2023



Miles et al.s data and results, titled The JWST Early Release Science
Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b, was published on March 22 in The Astrophysical Journal Letters.

Webb Measures the Temperature of an Exoplanet

In addition to Webbs groundbreaking observations of VHS 1256b, a second team of international scientists used Webbs MIRI to measure the temperature of a rocky exoplanet located approximately 40 light-years away from Earth. Named TRAPPIST-1b, the planet is part of the well-known TRAPPIST-1 system a collection of seven rocky exoplanets orbiting a red dwarf star.

While star systems of rocky exoplanets are not uncommon, the exoplanets of
the TRAPPIST-1 system are of particular interest to scientists because of their similarities in size and mass to the inner rocky planets of our solar system. Interestingly, the orbits of all seven exoplanets could fit within
the orbit of Mercury, but given the small size of their host star, the energy some of the planets receive is comparable to the energy Earth receives from the Sun.

TRAPPIST-1b, the innermost planet of the TRAPPIST-1 system, orbits at an orbital distance of about one-hundredth that of Earths, receiving nearly four times the amount of energy Earth receives from our Sun. Given TRAPPIST-1bs close proximity to its host star, it does not lay within TRAPPIST-1s
habitable zone. Nonetheless, any information collected on the planet will prove to be useful for scientists trying to characterize its sibling exoplanets and the evolution of the TRAPPIST-1 and other red dwarf systems. Artists illustration of TRAPPIST-1b, with red dwarf TRAPPIST-1 seen in the background. (Credit: NASA/ESA/CSA/J. Olmsted (STScI))

Its easier to characterize terrestrial planets around smaller, cooler stars. If we want to understand habitability around M stars, the TRAPPIST-1 system
is a great laboratory. These are the best targets we have for looking at the atmospheres of rocky planets, said co-author Elsa Ducrot of the French Alternative Energies and Atomic Energy Commission (CEA) in France.

Since their discovery in 2017, scientists have been trying to learn more
about each of the seven exoplanets. However, until last year, scientists
didnt have access to telescopes powerful enough to measure specific details
on each exoplanet.

With the release of Webbs first images in July 2022, several teams of scientists were already planning to use the telescope to observe the TRAPPIST-1 exoplanets. Thomas Greene, lead author of the study and scientist at NASAs Ames Research Center, and his international team of astrophysicists were one of those teams and were ready to utilize the mid-infrared capabilities of Webb and MIRI a capability which, to that point, had not
been available.

These observations really take advantage of Webbs mid-infrared capability. No previous telescopes have had the sensitivity to measure such dim mid-infrared light, Greene said.

Greene et al. made the temperature measurements by investigating the thermal emission, or the heat energy radiated by a planet, from TRAPPIST-1b. Planets radiate heat in the form of infrared light, and with Webbs incredible sensitivity to infrared light, measuring the thermal characteristics of TRAPPIST-1b was sure to yield impressive results.

The team found that TRAPPIST-1bs dayside temperature sits at about 500
Kelvin, or 227 degrees Celsius suggesting that the planet may not have an atmosphere. Former observations of TRAPPIST-1b using NASAs Hubble Space Telescope and infrared Spitzer Space Telescope found no evidence of an atmosphere around the exoplanet. However, the observations were not enough to completely rule out the possibility of a dense atmosphere existing around the planet. Graphic comparing the measured temperature of TRAPPIST-1b to computer models, Earth, and Mercury. (Credit: NASA/ESA/CSA/J. Olmsted (STScI)/Thomas Greene (NASA Ames)/Taylor Bell (BAERI)/Elsa Ducrot (CEA)/Pierre-Olivier
Lagage (CEA))

There are ten times as many of these [red dwarf] stars in the Milky Way as there are stars like the Sun, and they are twice as likely to have rocky planets as stars like the Sun. But they are also very active they are very bright when theyre young, and they give off flares and X-rays that can wipe out an atmosphere, Greene said.

For Greene et al. to determine the existence of an atmosphere around TRAPPIST-1b with confidence, they had to use the teams groundbreaking temperature measurement.

This planet is tidally locked, with one side facing the star at all times and the other in permanent darkness. If it has an atmosphere to circulate and redistribute the heat, the dayside will be cooler than if there is no atmosphere, said co-author Pierre-Olivier Lagage of CEA.

Webb collected the data used for the temperature measurement by performing a technique called secondary eclipse photometry. When using the technique, MIRI measured the change in brightness of the entire TRAPPIST-1 system as the planet moved behind the star. Given that TRAPPIST-1b emits its own infrared light, Greene et al. simply subtracted the light from only TRAPPIST-1 from
the light of both the planet and star combined to calculate the exact amount of infrared light being emitted by TRAPPIST-1b. To ensure their data was correct, the team collected and analyzed data for five secondary eclipses.

The total change in brightness between the star and the planet is less than 0.1%, once again highlighting the immense power and precision of Webb and its world-class suite of instruments.

There was also some fear that wed miss the eclipse. The planets all tug on each other, so the orbits are not perfect. But it was just amazing: The time of the eclipse that we saw in the data matched the predicted time within a couple of minutes, said researcher Taylor Bell of the Bay Area Environmental Research Institute, who performed data analysis for Greene et al. Graphic showing the light curve created by the secondary eclipse of TRAPPIST-1b
behind TRAPPIST-1. (Credit: NASA/ESA/CSA/J. Olmsted (STScI)/Thomas Greene (NASA Ames)/Taylor Bell (BAERI)/Elsa Ducrot (CEA)/Pierre-Olivier Lagage
(CEA))

We compared the results to computer models showing what the temperature
should be in different scenarios. The results are almost perfectly consistent with a blackbody made of bare rock and no atmosphere to circulate the heat.
We also didnt see any signs of light being absorbed by carbon dioxide, which would be apparent in these measurements, Ducrot explained.

As mentioned, the temperature measurement marks the first time any light emitted by a rocky exoplanet has been directly detected and measured by a telescope. Whats more, the temperature data is giving scientists valuable insights into red dwarf star systems and the characteristics of the
exoplanets that orbit them.

There was one target that I dreamed of having, and it was this one. This is the first time we can detect the emission from a rocky, temperate planet. Its a really important step in the story of discovering exoplanets, said Lagage, who assisted with the development of MIRI. TRAPPIST-1 b: We give it a one (M-dwarf) star review; it lacks atmosphere.

Webb found the dayside temperature of this rocky exoplanet to be about 450 F (227 C) suggesting it has no significant atmosphere: https://t.co/TGYqguDgT4

Heres why this is a big deal pic.twitter.com/7kW8nKxC4U

NASA Webb Telescope (@NASAWebb) March 27, 2023



The data used in Greene et al.s study was collected as part of Webbs Guaranteed Time Observation (GTO) program 1177. The program is one of eight planned GTO programs that are expected to further characterize and explore
the TRAPPIST-1 system and its exoplanets. Webb is currently performing additional secondary eclipse observations of TRAPPIST-1b, which scientists
are hoping will allow them to capture a full phase curve for the planet,
which would show how the brightness of the planet changes across its entire orbit of TRAPPIST-1. Having the data from a full phase curve would give scientists insight into how the planets temperature changes from TRAPPIST-1bs dayside and nightside allowing them to determine the existence of an atmosphere with high confidence.

Greene et al.s study, titled Thermal Emission from the Earth-sized Exoplanet TRAPPIST-1 b using JWST, was published in the journal Nature on March 27.

(Lead image: (top left) Artists illustration of VHS 1256b. (bottom right) Artists illustration of TRAPPIST-1b. Credit: NASA/ESA/CSA/Joseph Olmsted (STScI))

The post Using JWST, scientists observe silicate clouds and measure the temperature of exoplanets appeared first on NASASpaceFlight.com .



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