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Nearby Warm Neptune Has Sulfurous Atmosphere, Astronomers Say

by News7

A warm-Neptune exoplanet called GJ 3470b (Gliese 3470b) is 96 light-years away and circles a 2-billion-year-old red dwarf star in the general direction of the constellation Cancer.

An artist’s impression of the warm-Neptune exoplanet GJ 3470b. Image credit: Department of Astronomy, UW-Madison.

First discovered in 2012, GJ 3470b is the lightest and coldest (325 degrees Celsius, or more than 600 Fahrenheit) exoplanet to harbor sulfur dioxide.

The compound is likely a sign of the churn of active chemical reactions in the planet’s atmosphere, created when radiation from its nearby star blasts apart the components of hydrogen sulfide, which then go looking for new molecular partners.

“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, since it gives us a new way to figure out how these planets formed,” said University of Wisconsin-Madison’s Professor Thomas Beatty.

“And small planets are especially interesting, because their compositions are really dependent on how the planet-formation process happened.”

Professor Beatty and colleagues hope they will be able to do just that: figure out the recipe for planet formation by looking at what’s in exoplanets.

“Discovering sulfur dioxide in a planet as small as GJ 3470b gives us one more important item on the planet formation ingredient list,” Professor Beatty said.

In the case of GJ 3470b, there are also other interesting features that might help fill out that recipe.

The planet’s orbit around its star takes it nearly over the star’s poles, which is to say that it’s circling at a 90-degree angle to the expected path of planets in the system.

It’s also surprisingly close to the star, close enough that the light from its star is blowing copious amounts of GJ 3470b’s atmosphere away into space.

According to the team, the planet has probably lost about 40% of its mass since it was formed.

The close-in, off-kilter orbit is a sign that GJ 3470b used to be somewhere else in its system, and at some point, the planet became entangled with the gravity of another and was pulled into a new path that eventually settled it in a different neighborhood.

“That migration history that led to this polar orbit and the loss of all this mass — those are things we don’t typically know about other exoplanet targets we’re looking at,” Professor Beatty said.

“Those are important steps in the recipe that created this particular planet and can help us understand how planets like it are made.”

“With further analysis of the ingredients that remain in the planet’s atmosphere, GJ 3470b may help us understand how planets like it got to be so appetizing.”

The authors presented their findings this month at the 244th Meeting of the American Astronomical Society in Madison, Wisconsin.

Source : Breaking Science News

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