by Hot Neptune exoplanet It was found to contain sulfur dioxide in its atmosphere – an atmosphere that is also drifting into space as the planet bends over the poles of its star in a sharply inclined orbit every three and a third days.
The presence of sulfur dioxide in the atmosphere of the exoplanet, known as GJ 3470b and located 96 light year from Worldit came as a shock when he saw the James Webb Space Telescope (JWST).
“We didn’t think we’d see sulfur dioxide on planets this small, and it’s exciting to see this new molecule in a place we didn’t expect, because it gives us a new way to figure out how these planets formed ,” said Thomas Beatty of the University of Wisconsin, Madison in a statement. “And minor planets are especially interesting, because their composition is very dependent on how the planet formation process happened.”
Everything about GJ 3470b tells us that it has an interesting and eventful history.
Planet form in a disk of gas and dust that swirls around a plane aligned with the star’s rotating axis. In our Solar systemwe can see evidence of the disk in that the planets from mercury to Neptune orbit in the ecliptic plane. GJ 3470b, on the other hand, follows a path tilted 89 degrees to its spin axis red ox star. In other words, it is on a steep orbit that bends over the poles of the star. Planets do not normally form on such an orbit.
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With a mass 13.9 times more than the mass of the Earthand diameter about 40% that of Jupiter, GJ 3470b is a bloated bag of gas. When such life is close to its star, astronomers call it ‘hot Neptune’.” GJ 3470b has an atmospheric temperature of 325 degrees Celsius (617 degrees Fahrenheit); the temperature of Neptune in our solar system is -200 degrees Celsius (–330 degrees). Fahrenheit).
Current models of planet formation describe how gas giants usually form further out from their star than rocky planets, in the cold depth where gas is more abundant. However, GJ 3470b orbits at a distance of 5.3 million kilometers (3.3 million miles) from its star. By comparison, Mercury, the closest planet to us Sunorbits at an average distance of 58 million kilometers (36 million miles) from our star, although red dwarf systems are usually scaled down compared to our solar system.
Normally, we would expect GJ 3470b to be further out and to have migrated as a result of interactions with the planet-forming disk of its star. Meanwhile, scientists would normally suspect that the earth would have been thrown out of orbit by a gravitational interaction with another planet, or perhaps even a disturbance caused by a passing star.
However, the planet’s atmospheric composition suggests otherwise.
Despite JWST’s detection of internal molecules, such as sulfur dioxide, GJ 3470b’s atmosphere is still largely made of hydrogen and helium, even more so than the gas planets in our solar system – a fact seen by the solar system. Hubble Space Telescope in 2019. So the explanation forwarded that is, GJ 3470b formed close to its star as a rocky planet before accreting a thick atmosphere of almost pure hydrogen and helium – but, at the moment, this is only a hypothesis. That’s why detecting sulfur dioxide at JWST is so important, as its presence could help distinguish between different theories of how the planet formed.
The detection of sulfur dioxide came to light thanks to GJ 3470b transiting its star, which allows astronomers to do what is called “transmission spectroscopy”. As light from its parent star shines through GJ 3470b’s atmosphere, molecules in the earth’s atmosphere absorb some of the starlight, leaving dark absorption lines in the star’s spectrum.
However, these absorption lines are difficult to tease out, especially for a hot Neptune that is likely shrouded in a featureless nebula.
“The thing is that everybody looks at these planets and everybody often sees flat lines,” Beatty said. “But when we looked at this planet, we didn’t really find a flat line.”
Instead, the JWST was able to confirm absorption lines from carbon dioxide, methane and water vapor, and indeed detect sulfur dioxide in the region for the first time. time. This makes GJ 3470b the lightest and coolest exoplanet yet known to have a sulfur dioxide atmosphere. Previous observations have linked Jupiter’s hot atmosphere with temperatures over a thousand degrees Celsius (1,830 degrees Fahrenheit).
“Finding sulfur dioxide in a planet as small as GJ 3470b gives us one more important item on the list of planet-forming ingredients,” Beatty said.
The sulfur probably started out as a component in hydrogen sulfide, the team says. However, because GJ 3470b passes so close to its star, ultraviolet light from the star’s body packs a powerful enough punch to easily break apart atmospheric molecules, resulting in a kind of chemical meltdown made of molecular components broken reconnecting together. atoms and molecules. A sulfur atom combined with two oxygen atoms makes sulfur dioxide.
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The planet’s parent star doesn’t just break up atmospheric molecules, though; hydrogen freed from those molecules can be completely removed from the planet. GJ 3470b is literally like that evaporate before our very eyes, the stellar wind gradually blew its atmosphere away into space, leaving behind a stream of hydrogen gas. Already, the planet has lost about 40% of its original mass.
The presence of sulfur dioxide in its atmosphere, the still unexplained tilted orbit and the ever-changing mass loss of GJ 3470b are significant clues to the origin of this strange and wonderful planet, according to Beatty.
“Those are important steps in the recipe that created this particular planet and can help us understand how planets like it are made,” he said.
Beatty presented the findings at the 244th meeting of the American Astronomical Society on June 10, and they were accepted for publication in Astrophysical Journal Letters.
