- 3665 - EXOPLANET - covered in water? As of August , 2022, there are 5,125 confirmed exoplanets in 3,794 planetary systems, with 829 systems having more than one planet. Most of these were discovered by the Kepler space telescope. There is much anticipation about discoveries coming from the new James Webb Telescope.
--------------------- 3665 - EXOPLANET - covered in water?
- After years of preparation and anticipation, exoplanet researchers are ecstatic. NASA’s James Webb Space Telescope has captured an astonishingly detailed rainbow of near-infrared starlight filtered through the atmosphere of a hot gas giant 700 light-years away.
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- The transmission spectrum of exoplanet “WASP-39 b“, based on a single set of measurements made using Webb’s Near-Infrared Spectrograph and analyzed by dozens of scientists, represents a hat trick of firsts:
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----------------- Webb’s first official scientific observation of an exoplanet;
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---------------- The first detailed exoplanet spectrum covering this range of near-infrared colors;
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---------------- The first indisputable evidence for carbon dioxide in the atmosphere of a planet orbiting a distant star.
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- The results are indicative of Webb’s ability to spot key molecules like carbon dioxide in a wide variety of exoplanets, including smaller, cooler, rocky planets, providing insights into the composition, formation, and evolution of planets across the galaxy.
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- A transmission spectrum of the hot gas giant exoplanet WASP-39 b captured by Webb’s Near-Infrared Spectrograph (NIRSpec) on July 10, 2022, reveals the first clear evidence for carbon dioxide in a planet outside the solar system.
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- This is also the first detailed exoplanet transmission spectrum ever captured that covers wavelengths between 3 and 5.5 microns.
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- This observation of a gas giant planet orbiting a Sun-like star 700 light-years away provides important insights into the composition and formation of the planet. The finding is also indicative of Webb’s unique ability to detect and measure carbon dioxide in the thinner atmospheres of smaller, rocky planets.
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- WASP-39 b is a hot gas giant with a mass roughly one-quarter that of Jupiter, about the same as Saturn, and a diameter 1.3 times greater than Jupiter. Its extreme puffiness is related in part to its high temperature, 1,600 degrees Fahrenheit.
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- Unlike the cooler, more compact gas giants in our solar system, WASP-39 b orbits very close to its star, only about one-eighth the distance between the Sun and Mercury, completing one circuit in just over four Earth-days. The planet’s discovery was made based on ground-based detections of the subtle, periodic dimming of light from its host star as the planet transits, or passes in front of the star.
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- A series of light curves from Webb’s Near-Infrared Spectrograph (NIRSpec) shows the change in brightness of three different wavelengths (colors) of light from the WASP-39 star system over time as the planet transited the star on July 10, 2022.
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- A transit occurs when an orbiting planet moves between the star and the telescope, blocking some of the light from the star. This observation was made using the NIRSpec PRISM bright object time-series mode, which involves using a prism to spread out light from a single bright object (like the star WASP-39) and measure the brightness of each wavelength at set intervals of time.
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- To capture these data, Webb stared at the WASP-39 star system for more than eight hours, beginning about three hours before the transit and ending about two hours after the transit was complete. The transit itself lasted about three hours.
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- Each light curve includes a total of 500 individual brightness measurements, about one per minute. Although all colors are blocked to some extent by the planet, some colors are blocked more than others. This occurs because each gas in the atmosphere absorbs different amounts of specific wavelengths. As a result, each color has a slightly different light curve.
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- Previous observations from other telescopes, including NASA’s Hubble and Spitzer space telescopes, revealed the presence of water vapor, sodium, and potassium in the planet’s atmosphere. Webb’s unmatched infrared sensitivity has now confirmed the presence of carbon dioxide on this planet as well.
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- Astronomers have also discovered an exoplanet that could be completely covered in water. The Institute for Research on Exoplanets (iREx), has announced the discovery of an exoplanet orbiting “TOI-1452“, one of two small stars in a binary system located in the Draco constellation about 100 light-years from Earth.
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- The exoplanet is slightly greater in size and mass than Earth and is located at distance from its star where its temperature would be neither too hot nor too cold for liquid water to exist on its surface. The astronomers believe it could be an “ocean planet,” a planet completely covered by a thick layer of water, similar to some of Jupiter’s and Saturn’s moons.
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- It was NASA’s space telescope TESS, which surveys the entire sky in search of planetary systems similar to our own, that put the researchers on the trail of TOI-1452 b. Based on the TESS signal, which showed a slight decrease in brightness every 11 days, astronomers predicted a planet that has a diameter about 70% larger than that of Earth.
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- After confirming the nature of their signal and estimating the planet’s radius astronomers made sure the signal detected by TESS was really caused by an exoplanet circling TOI-1452, the largest of the two stars in that binary system.
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- The host star is much smaller than our Sun and is one of two of similar size stars in a binary system. The two stars orbit each other and are separated by such a small distance, 97 astronomical units, or about two and a half times the distance between the Sun and Pluto.
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- With resolution is high enough to distinguish the two objects, and the images showed that the exoplanet does orbit TOI-1452. To determine the planet’s mass, the researchers then observed the system with SPIRou, an instrument installed on the Canada-France-Hawaii Telescope in Hawai’i. SPIRou is ideal for studying low-mass stars because it operates in the infrared spectrum, where these stars are brightest.
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- Even then, it took more than 50 hours of observation to estimate the planet’s mass, which is believed to be nearly five times that of Earth. Astronomers cleaned the data obtained with SPIRou of many parasite signals to reveal the weak signature of planets.
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- The watery world is probably rocky like Earth, but its radius, mass, and density suggest a world very different from our own. Earth is essentially a very dry planet; even though we sometimes call it the Blue Planet because about 70% of its surface is covered by ocean, water actually only makes up only a negligible fraction of its mass, less than 1%.
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- Water may be much more abundant on some exoplanets. In recent years, astronomers have identified and determined the radius and mass of many exoplanets with a size between that of Earth and Neptune which is 3.8 times larger than Earth.
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- Some of these planets have a density that can only be explained if a large fraction of their mass is made up of volatiles such as water.
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- This planet is one of the best candidates for an ocean planet that we have found to date. Its radius and mass suggest a much lower density than what one would expect for a planet that is basically made up of metal and rock, like Earth.
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- Water may make up as much as 30% of its mass, a proportion similar to that of some natural satellites in our Solar System, such as Jupiter’s moons Ganymede and Callisto, and Saturn’s moons Titan and Enceladus.
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- This exoplanet is a perfect candidate for further observation with the James Webb Space Telescope. It is one of the few known temperate planets that exhibit characteristics consistent with an ocean planet. It is close enough to Earth that researchers can hope to study its atmosphere and test this hypothesis. And, it is located in a region of the sky that the telescope can observe year round.
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- Observations with the Webb Telescope will be essential to better understanding TOI-1452 b. As soon as astronomers can, they will book time on the Webb to observe this strange and wonderful world. More news to follow shortly.
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August 27, 2022 EXOPLANET - covered in water? 3663
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