Astronomers Complete Most Detailed Weather Map Ever For An Exoplanet

Chuck Bednar for redOrbit.com – Your Universe Online
Using observations from the NASA’s Hubble Space Telescope, a team of astronomers has managed to create the most detailed map ever of an exoplanet’s air temperature and water vapor, officials from the US space agency announced Thursday.
The target of the investigation, which is detailed in the October 9 edition of Science Express, was WASP-43b – a hot-Jupiter exoplanet said to have winds that travel the speed of sound, a ‘day’ side with temperatures of 3,000 degrees Fahrenheit and a pitch-black ‘night’ side with temperatures dipping below 1,000 degrees Fahrenheit.
WASP-43b, which was first discovered in 2011, is a planet roughly the same size as Jupiter but with twice the mass and an orbit much closer to its parent star than any planet in the Solar System, the researchers explained. It is located 260 light-years away and has one of the shortest years (19 hours) of any exoplanet of its size.
“Our observations are the first of their kind in terms of providing a two-dimensional map of the planet’s thermal structure,” lead author Kevin Stevenson from the University of Chicago explained in a statement. “These maps can be used to constrain circulation models that predict how heat is transported from an exoplanet’s hot day side to its cool night side.”
The planet, which is predominately hot hydrogen gas and lacking surface features such as oceans and continents, has different day and night sides because it is tidally locked, which means that it keeps one hemisphere facing the star it orbits. Furthermore, this study also marked the first time astronomers were able to observe three complete rotations of any single planet – a feat which occurred in a span of just four days, the researchers said.
[ Watch the Video: Time-lapse video of WASP-43b over one planet rotation ]
In order to study WASP-43b’s atmosphere, Stevenson and his colleagues used two previous methods of analyzing exoplanets for the first time. They used a technique called transmission spectroscopy to determine the water abundance on the atmosphere on the boundary between the day and night hemispheres, then measured the water abundances and temperatures at different longitudes in order to make the map more detailed.
In measuring the water abundances and temperatures at different longitudes, the investigative team utilized the precision and stability of Hubble’s instruments to subtract more than 99.95 percent of the light from the parent star, allowing them to study the light coming from the planet itself. This technique, which is called emission spectroscopy, allowed them to map the atmosphere at different points of the planet’s orbit around its parent star.
“These observations allow us to determine the abundance of water in the planet’s atmosphere, which is a major element involved in planetary formation,” second author Jean-Michel Désert of the University of Colorado-Boulder Department of Astrophysical and Planetary Sciences said in a statement. “By measuring the composition of this planet, we will have a better idea where it formed within the proto-planetary disk of the host star.”
The researchers discovered that WASP-43b reflected very little of its host star’s light, and while they did not find an atmosphere like Earth’s, they did detect water vapor in the planet’s atmosphere. Since the planet is so hot, all of the water in its atmosphere is vaporized, instead of condensed into icy clouds like on Jupiter, the study authors noted.
Scientists have long believed that water plays a key role in the formation of giant planets like WASP-43b, and they theorize that comet-like bodies bombard young planets, bringing with them the majority of the water and other molecules that they observe. However, the water abundances in the Solar System’s giant planets are poorly known because much of the water is locked away as ice, deep in the atmosphere and hard to identify.
“Space probes have not been able to penetrate deep enough into Jupiter’s atmosphere to obtain a clear measurement of its water abundance. But this giant planet is different,” said co-author Derek Homeier of the École Normale Supérieure de Lyon in France. Since WASP-43b’s water is in the form of vapor, it could be “more easily traced,” Homeier added that the scientists could find it, directly measure it and test for longitudinal variations.
“In order to understand how giant planets form astronomers want to know how enriched they are in different elements,” NASA added. “The team found that WASP-43b has about the same amount of water as we would expect for an object with the same chemical composition as our sun, shedding light on the fundamentals about how the planet formed. The team next aims to make water-abundance measurements for different planets.”
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