Water vapor glowing in the atmosphere around a newly discovered exoplanet suggests the alien world boasts a stratosphere. Photo by Engine House VFX/At-Bristol Science Centre/University of Exeter
Aug. 2 (UPI) -- Scientists have discovered evidence of a stratosphere surrounding a large exoplanet located 900 light-years from Earth.
A team of astronomers from the University of Exeter and the University of Maryland discovered glowing water molecules while surveying Hubble's observations of WASP-121b's atmosphere.
"When it comes to distant exoplanets, which we can't see in the same detail as other planets here in our own solar system, we have to rely on proxy techniques to reveal their structure," Drake Deming, a professor of astronomy at Maryland, said in a news release. "The stratosphere of WASP-121b so hot it can make water vapor glow, which is the basis for our analysis."
Water molecules interact with certain wavelengths of light in predictable ways. At cooler temperatures, water molecules block light. At higher temperatures, water molecules radiate or shimmer.
As water molecules are heated and vaporized, their electrons move into higher energy states. As they do, they emit infrared light. Scientists were able to identify the phenomenon in spectral data collected by Hubble.
"This new research is the smoking gun evidence scientists have been searching for when studying hot exoplanets," said David Sing, an associate professor of astrophysics at the University of Exeter. "We have discovered this hot Jupiter has a stratosphere, a common feature seen in most of our solar system planets."
WASP-121b is so hot because it orbits so close to its host star. If the star and exoplanet were any closer, the star's gravity would likely rip WASP-121b to shreds.
The temperature of Earth's stratosphere is stratified, it gets warmers as the stratosphere extends away from Earth. Ozone in the layers closer to the sun absorb more heat from solar radiation. Methane in the stratosphere of Jupiter and Saturn's moon Titan has a similar effect.
Researchers believe WASP-121b is host to a similar stratification, only more dramatic. Most stratospheres feature a temperature difference of 100 degrees Celsius. The stratosphere of the newly discovered exoplanet features a temperature difference of 1,000 degrees Celsius.
"We've measured a strong rise in the temperature of WASP-121b's atmosphere at higher altitudes, but we don't yet know what's causing this dramatic heating," said Nikolay Nikolov, a research fellow at Exeter. "We hope to address this mystery with upcoming observations at other wavelengths."
Researchers described their analysis of WASP-121b's atmosphere this week in the journal Nature.