- 3756 - EXOPLANET - atmospheres detected by Webb! The James Webb Space Telescope just scored another first making a molecular and chemical portrait of a distant planet‘s atmosphere.
---------------- 3756 - EXOPLANET - atmospheres detected by Webb!
- While Webb and other space telescopes, the Hubble Space Telescope, have previously revealed isolated ingredients of this heated planet’s atmosphere, the new readings provide a full menu of atoms, molecules, and even signs of active chemistry and clouds.
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- The latest data from the Webb instruments give a hint of how these clouds might look up close: broken up rather than as a single, uniform blanket over the planet. The telescope’s array of highly sensitive instruments is trained on the atmosphere of
“WASP-39 b“. Measuring the atmosphere of another world. Amazing!
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- WASP-39 b“ is a “hot Saturn”, a planet about as massive as Saturn but in an orbit tighter than Mercury orbiting a star that is some 700 light-years away. This Saturn-sized exoplanet was one of the first examined by the James Webb Space Telescope when it began regular science operations this summer, 2022.
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- Webb’s exquisitely sensitive instruments have provided a profile of WASP-39 b’s atmospheric constituents and identified a plethora of contents, including water, sulphur dioxide, carbon monoxide, sodium and potassium. WASP-39 is the star. “a’, “b”, “c” designate the planets circling the star
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- These findings bode well for the capability of Webb’s instruments to conduct the broad range of investigations of exoplanets around other stars that includes probing the atmospheres of smaller, rocky planets like those in the TRAPPIST-1 system.
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- Among the unprecedented revelations is the first detection in an exoplanet atmosphere of sulfur dioxide, a molecule produced from chemical reactions triggered by high-energy light from the planet’s parent star. On Earth, the protective ozone layer in the upper atmosphere is created in a similar way.
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- This is the first time scientists have seen concrete evidence of photochemistry, chemical reactions initiated by energetic stellar light, on exoplanets. Scientists applying computer models of photochemistry to data that require such physics to be fully explained. Planets are sculpted and transformed by orbiting within the radiation bath of the host star. On Earth, those transformations allow life to thrive, somehow?
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- The planet’s proximity to its host star is eight times closer than Mercury is to our Sun. This makes it a laboratory for studying the effects of radiation from host stars on exoplanets. Better knowledge of the star-planet connection should bring a deeper understanding of how these processes affect the diversity of planets observed in the over 5,000 exoplanets so far discovered in the Milky Way galaxy.
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- Other atmospheric constituents detected by the Webb telescope include sodium (Na), potassium (K), and water vapor (H2O), confirming previous space- and ground-based telescope observations as well as finding additional fingerprints of water, at these longer wavelengths, that haven’t been seen before.
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- Webb also saw carbon dioxide (CO2) at higher resolution, providing twice as much data as reported from its previous observations. Meanwhile, carbon monoxide (CO) was detected, but obvious signatures of both methane (CH4) and hydrogen sulphide (H2S) were absent from the Webb data.
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- To capture this broad spectrum of WASP-39 b’s atmosphere, an international team numbering in the hundreds independently analyzed data from four of the Webb telescope’s finely calibrated instrument modes.
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- Having such a complete roster of chemical ingredients in an exoplanet atmosphere also gives scientists a glimpse of the abundance of different elements in relation to each other, such as the carbon-to-oxygen or potassium-to-oxygen ratios. That in turn provides insight into how this planet formed out of the disc of gas and dust surrounding the parent star in its younger years.
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- WASP-39 b’s chemical inventory suggests a history of smashups and mergers of smaller bodies called planetesimals to create an eventual goliath of a planet. The abundance of sulfur relative to hydrogen indicated that the planet presumably experienced significant accretion of planetesimals that can deliver these ingredients to the atmosphere.
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- The data also indicates that the oxygen is a lot more abundant than the carbon in the atmosphere. This potentially indicates that WASP-39 b originally formed far away from the central star and then gradually reduced its orbit.
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- A transmission spectrum is made by comparing starlight filtered through a planet’s atmosphere as it moves in front of the star, to the unfiltered starlight detected when the planet is beside the star. Each of the data points on these spectrum graphs represents the amount of a specific wavelength of light that is blocked by the planet and absorbed by its atmosphere. Wavelengths that are preferentially absorbed by the atmosphere appear as peaks in the transmission spectrum.
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- A best-fit model is created that takes into account the data, the known properties of WASP-39 b and its star (e.g., size, mass, temperature), and assumed characteristics of the atmosphere. Researchers can vary the parameters in the model, changing unknown characteristics like cloud height in the atmosphere and abundances of various gases, to get a better fit and further understand what the atmosphere is really like.
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- The above graph displays data from Webb's NIRSpec instrument, indicating signatures of potassium (K), water (H2O), carbon monoxide (CO), sulfur dioxide (SO2), carbon dioxide (CO2), and sodium (Na).
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- The radial velocity (RV) method to detect an exoplanet is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an unseen exoplanet as it orbits the star. Using this technique, more than 600 exoplanets have been detected to date, 2022.
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- Finding of a new giant planet as a result of RV measurements using the HIgh Dispersion Echelle Spectrograph (HIDES) at Okayama Astrophysical Observatory (OAO) in Japan. The planet orbits a deeply evolved solar-mass G-type giant star known as HD 167768, located some 353 light years away.
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- The newly detected exoplanet, designated HD 167768 b, is estimated to have a mass of at least 0.85 Jupiter masses. It orbits its host every 20.65 days, at a distance of 0.15 AU, Astronomical Units, which is the earth-Sun distance, 93 million mile. The equilibrium temperature of this planet was calculated to be 1,874 Kelvin.
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- Classified “HD 167768 b” as a "warm Jupiter." The planet has turned out to have one of the shortest orbital periods among those ever found around deeply evolved stars using radial velocity methods.
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- The host star HD 167768, estimated to be 5.3 billion years old, is of spectral type G8 III, has a mass of around 1.08 solar masses, and is nearly 10 times larger than the sun. It has an effective temperature of 4,851 Kelvin, and its metallicity is at a level of -0.75.
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- Given that HD 167768 is expected to ascend the red giant branch, the astronomers predict that its planet will be swallowed in a relatively short time in astronomical terms. By analyzing the orbital evolution, they estimate that HD 167768 b will be engulfed by the expanding star within 150 million years.
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- The researchers also assume that at least two other planets may be present in the HD 167768 system, still undetected. This assumption is based on the two additional regular variations identified in the RV measurements. The more we learn the more we see that still needs to be learned.
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November 24, 2022 EXOPLANET - atmospheres detected by Webb! 3756
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