Hubble Spies a Glowing Stratosphere on a Giant Exoplanet

Fagjun | Published 2017-09-02 01:11

Image by Engine House VFX, At-Bristol Science Centre, University of Exeter


WASP-121b, a giant, superhot exoplanet, may have a stratosphere just like Earth does. Astronomers report that Hubble detected signatures of glowing molecules ringing the planet, which alerted observers to the presence of a stratosphere.


This large alien planet belongs to a group called “hot Jupiters”, which sounds like the name for an all-male burlesque group. In actuality, it's a group of large planets with high temperatures, making them easy to observe and study. The discovery that WASP-121b has a stratosphere is significant in that it shows us that planets outside our solar system can have a stratosphere as well.


The stratosphere is the second major layer of the Earth's atmosphere. It has a stratified temperature, with the upper parts being higher in temperature than the lower parts. Astronomers detected the same kind of temperature stratification on WASP-121b. The signatures of the water molecules in the atmosphere indicated that the upper layers of the atmosphere have a higher temperature than the lower ones do.


The Hot Jupiter Exoplanet

An artist's rendering of a hot Jupiter [Image by NASA, ESA & G. Bacon]


WASP-121b is a gas giant that orbits its host star, WASP-121, quite closely. In fact, the planet completes its orbit only in about a day and a third. If it came any closer to its star, the star's gravity would tear it apart. The star system lies 881 light years away from Earth, in the constellation Puppis.


Since WASP-121b is so close to its host star, it only makes sense that its atmosphere is quite hot. Estimates put the planet's temperature at about 2,500 degrees Celsius. On Earth, this high of a temperature would be enough to boil some metals.


Studying an exoplanet can be challenging. For one thing, exoplanets are often too far away for astronomers to gain much information. As of now, therefore, our knowledge about exoplanets is somewhat limited. However, if you're the type to follow news and updates about worlds beyond our solar system, then you're living in quite an amazing time. You're basically learning about exoplanets just a couple of steps behind the astronomers that study them.


"By looking at the difference in the brightness of the system for when the planet was not behind the star and when it was behind the star, we were able to work out the brightness and the spectrum of the planet itself," said Thomas Evans, who led the research.


Anticipating the James Webb Space Telescope

The mirror segments of the the James Webb Space Telescope[[Photo byNASA/MSFC/David Higginbotham/Emmett Given]


Though astronomers suspect that other exoplanets may be able to host life, WASP-121b is not one of those planets. It may have an atmosphere and a stratosphere like Earth, but it is too close to its host star. Temperatures at the surface of the planet, therefore, are bound to be way too hot for any form of life to survive.


The planet's stratosphere is so hot that its water vapor glows. Unfortunately, the glow isn't visible to the naked eye, but the Hubble Telescope was able to easily detect it. Evans plans on studying the exoplanet further, and hopes to be able to use NASA's James Webb Space Telescope after it launches next year. This telescope is set to be the most powerful telescope ever built.

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