Glowing Water Atmosphere Detected On A Planet Beyond Solar System

Posted: Aug 3 2017, 10:29pm CDT | by , in News | Latest Science News

 
Glowing Water Atmosphere Detected on a Planet Beyond Solar System
"Hot Jupiter" exoplanet named WASP-121b (left) has a stratosphere hot enough to boil iron. The planet is seen close to its host star (right). Credit: University of Exeter

This is the first time an exoplant is found with stratosphere, a layer seen in most of our solar system planets

Astronomers have found strong evidence for stratosphere on an exoplanet known as WASP-121b. This marks the first detection of watery atmosphere on a planet outside our solar system and it could reveal more about the nature of the exoworld's atmosphere.

Located approximately 900 light years from Earth, WASP-121b is a giant exoplanet. Although it has a larger mass and radius than Jupiter, the exoplanet is still classified as a ‘hot Jupiter.’ The exoplanet orbits its host star every 1.3 days. The host star begins to rip exoplanet apart when it reaches the point of closest approach. This proximity also means that the top layer of the atmosphere has turned blazing hot with an atmosphere hot enough to boil iron.

To study the exoplanet’s stratosphere, researchers usually look for the presence of water molecules and use spectroscopy to analyze changes in planet’s brightness at different wavelengths of light. Spectroscopy is a technique of studying the interaction between light and matter.

Water molecules in a planet's atmosphere behave differently in response to different wavelengths of light, depending on the temperature of the water. While cooler water vapors blocks light of specific wavelengths, water vapors with higher temperature cause them to glow at these wavelengths instead. The phenomenon follows the same principle as fireworks. But it was not visible to naked eye. Because the glow was in the form of infrared light, the team detected it in WASP – 121b's atmosphere by using NASA's Hubble Space Telescope.

"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," said co-author said Drake Deming from University of Maryland. "The stratosphere of WASP-121b so hot it can make water vapor glow, which is the basis for our analysis."

Earth atmosphere also has stratosphere. Ozone in Earth’s stratosphere traps ultraviolet radiation from the sun, which in turn increases the temperature of the layer. Other solar system bodies like Jupiter and Saturn’s moon Titan have stratospheres, too. The change in temperature within a stratosphere is typically less than 100 degrees Celsius. However, on WASP-121b, the temperature in the stratosphere rises in excess to 1000 Celsius.

"Theoretical models have suggested that stratospheres may define a special class of ultra-hot exoplanets, with important implications for the atmospheric physics and chemistry," said lead researcher Dr Tom Evans from University of Exeter. "When we pointed Hubble at WASP-121b, we saw glowing water molecules, implying that the planet has a strong stratosphere."

Researchers are not sure what causes this strong rise in temperature of WASP-121b's atmosphere but they believe further research could help unlock the mystery.

"This new research is the smoking gun evidence scientists have been searching for when studying hot exoplanets. We have discovered this hot Jupiter has a stratosphere, a common feature seen in most of our solar system planets." said co author of the study Professor David Sing from University of Exeter.

"It's a truly exciting find as we're seeing dramatic differences planet-to-planet which is giving valuable clues in figuring out how planets behave under different conditions, and we're only just scratching the surface of all the new Hubble data."

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