The sulfur-rich atmosphere discovered on the gaseous exoplanet GJ 3470 b, shown here in an illustration orbiting its star in the constellation Cancer, may help researchers understand how it (and similar planets) formed ). Credit: University of Wisconsin-Madison, edited
GJ 3470 b is a gas dwarf with sudden sulfur dioxide in its atmosphere. This discovery provides insights into planet formation and chemical reactions.
A startling yellow haze of sulfur dioxide in the atmosphere of a gas “dwarf”. exoplanets about 96 light-years away from our solar system makes the planet a prime target for scientists trying to understand how worlds formed.
Astronomers discovered the planet, GJ 3470 b, in 2012 when the planet’s shadow crossed the star it orbits. GJ 3470 b is located in the constellation of Cancer and is about half the size of Neptune, with a mass 10 times greater than Earth. In past years, researchers have compiled data on the planet using the Hubble and Spitzer space telescopes, culminating in a recent pair of observations with the James Webb Space Telescope.
Understanding exoplanet formation
Planets outside our solar system – called exoplanets – like GJ 3470 b are interesting subjects for researchers who wonder how planets form. Ideally, astronomers capture light from a star shining at the edge of the planet’s atmosphere. This allows them to collect a measure of the constituent light, or its spectrum, a reading marked by the characteristic spikes and dips of interesting molecules found in that atmosphere.
Thomas Beatty is an assistant professor of astronomy at the University of Wisconsin-Madison. Credit: University of Wisconsin-Madison
Sulfur dioxide: A rare find
“The thing is, everybody looks at these planets, and often everybody sees flat lines,” says University of Wisconsin-Madison astronomy professor Thomas Beatty. “But when we looked at this planet, we really it didn’t take a flat line.”
They saw evidence of water, carbon dioxide, methane and sulfur dioxide, findings that Beatty presented today in Madison at the 244th meeting of the American Astronomical Society and will soon publish in Astrophysical Journal Letters with co-authors from Arizona State University, University of Arizona, NASA‘s Ames Research Center and other organizations.
Coolest sulfur dioxide exoplanet
GJ 3470 b is the lightest and coolest (on average only 325 degrees centigradeor more than 600 Fahrenheit) exoplanet containing sulfur dioxide. The compound is likely a sign of an influx of active chemical reactions in the planet’s atmosphere, created when radiation from its nearby star breaks apart hydrogen sulfide compounds, which then go in search of new molecular partners.
“We didn’t think we’d see sulfur dioxide on such small planets, and it’s exciting to see this new molecule in a place we didn’t expect, as it gives us a new way to understand how these planets formed.” says Beatty, who worked as an instrument scientist at The James Webb Space Telescope before joining the UW–Madison faculty. “And minor planets are particularly interesting because their compositions really depend on how the planet formation process happened.”
The process of planet formation
Predicting this process is a focus of Beatty’s research. It’s a bit like spying on a baker just at the start of their work and then again when it’s time for dessert.
“Layed out on our table, we have all the ingredients that go into a cake and we have a finished cake,” he says. “Now, can we figure out the recipe—the steps that turned the raw materials into the final product—by measuring what’s in the cake?”
Astronomers like Beatty hope to be able to do just that: figure out the recipe for planet formation by looking at what’s in exoplanets.
“The discovery of sulfur dioxide in a planet as small as GJ 3470 b gives us a more important item on the list of planet-forming ingredients,” says Beatty.
Unique history of orbit and migration
In the case of GJ 3470 b, there are other interesting features that may help fill that prescription. The planet’s orbit around its star takes it almost over the star’s poles, meaning it is rotating at a 90-degree angle to the expected path of the planets in the system. It is also surprisingly close to the star, so close that the light from its star is blowing copious amounts of GJ 3470 b’s atmosphere far into space. The planet has probably lost about 40 percent of its mass since it formed.
The close, out-of-bounds orbit is a sign that GJ 3470 b was once elsewhere in its system, and at some point, the planet tangled with another’s gravity and was pulled into a new path that eventually settled it. in another neighborhood.
“That migration history that led to this polar orbit and the loss of all this mass — these are things that we don’t usually know about other exoplanet targets that we’re looking at,” says Beatty. “These are important steps in the recipe that created this particular planet and can help us understand how such planets form.”
With further analysis of the components remaining in the planet’s atmosphere and help from colleagues like those at UW–Madison’s Wisconsin Center for Origins Research, who specialize in protoplanetary disks and migration dynamics, GJ 3470 b may help Beatty and others to understand how the planets as if it was so delicious – at least from the point of view of astronomers.
This research was supported by grants from NASA.
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