Astronomers at the Massachusetts Institute of Technology have gained the clearest idea of the eternal dark side of the exoplanet, which is “tidily attached” to its star. Their observations combined with measurements of the planet’s constant daytime give a first detailed view of the exoplanet’s global atmosphere.
“We are now going beyond isolated images of specific regions of the exoplanet’s atmosphere to study them as the 3D systems they really are,” said Thomas Michal-Evans, who led the study as a postdoc at the Cowley Institute of Astrophysics and Space. institute. Research.
The planet is at the center of a new study that is in Astronomy of nature, is WASP-121b, a massive gas giant nearly twice the size of Jupiter. The planet is an ultra-hot Jupiter and was discovered in 2015, orbiting a star around 850 light years from Earth. WASP-121b has one of the shortest orbits discovered to date, orbiting its star in just 30 hours. It is also tidal closed, so that its star-facing “day” side is constantly fried, and its “night” side is forever turned into space.
“Hot Jupiters are known to have very bright day sides, but the night side is a different beast. The night side of WASP-121b is about 10 times weaker than its day side, ”says Tansu Daylan, TESS postdoc at the Massachusetts Institute of Technology, co-author of the study.
Earlier, astronomers detected water vapor and studied how the temperature of the atmosphere changes with altitude on the day side of the planet.
The new study paints a much more detailed picture. The researchers were able to map the sharp changes in temperature from day to night and see how these temperatures change with altitude. They also monitored the presence of water in the atmosphere to show for the first time how water circulates between the day and night sides of the planet.
While on Earth water circulates, first evaporating, then condensing into clouds and then raining, on WASP-121b the water cycle is much more intense: on the day side the atoms that make up water are torn apart at temperatures above 3,000 degrees. Kelvin. These atoms are carried to the night side, where colder temperatures allow hydrogen and oxygen atoms to recombine into water molecules, which then return to the day side, where the cycle begins again.
The team estimated that the water cycle on the planet is supported by winds that break atoms around the planet at speeds of up to 5 kilometers per second, or more than 11,000 miles per hour.
It also seems that water is not just circulating around the planet. Astronomers have found that the night side is cold enough to accommodate exotic clouds of iron and corundum – the mineral that makes up rubies and sapphires. These clouds, like water vapor, can spill over to the day side, where high temperatures convert metals into gaseous form. Exotic rain, such as liquid gemstones from corundum clouds, is possible along the way.
“With this observation, we really get a global picture of the meteorology of the exoplanet,” says Michal-Evans.
The study was co-authored by staff at the Massachusetts Institute of Technology, Johns Hopkins University, Caltech and other institutions.
Day and night
The team observed WASP-121b using a spectroscopic camera aboard NASA’s Hubble Space Telescope. The instrument observes the light of the planet and its stars and breaks this light into component wavelengths, the intensity of which gives astronomers the keys to the temperature and composition of the atmosphere.
Using spectroscopic studies, scientists have observed details of the atmosphere on the day sides of many exoplanets. But doing the same for the night side is much harder, as you need to watch for small changes across the entire spectrum of the planet as it revolves around its star.
For the new study, the team observed WASP-121b for two full orbits, one in 2018 and the other in 2019. For both observations, the researchers reviewed data on light for a specific line or spectral feature that indicates the presence of water vapor.
“We saw this water body and mapped out how it has changed in different parts of the planet’s orbit,” says Michal-Evans. “It encodes information about what makes the planet’s atmosphere temperature dependent on altitude.”
Change water The feature helped the team display the temperature profile of both the day and night sides. They found that daytime temperatures ranged from 2,500 Kelvin in the deepest observed layer to 3,500 Kelvin in its upper layers. The night side ranged from 1,800 Kelvin in the deepest layer to 1,500 Kelvin in the upper atmosphere. Interestingly, the temperature profiles seemed to shift, increasing with altitude on the day side – “thermal inversion”, in meteorological terms – and decreasing with altitude on the night side.
The researchers then passed temperature maps through various models to determine the chemicals that are likely to exist in the planet’s atmosphere, given certain altitudes and temperatures. This simulation revealed the potential of metallic clouds such as iron, corundum and titanium on the night side.
From them temperature map, the team also noticed that the hottest area of the planet is shifting east of the “spy” area just below the star. They concluded that this shift is due to strong winds.
“The gas heats up at the sub-star point, but blows to the east before it can be radiated into space,” explains Michal-Evans.
Based on the size of the change, the team estimates that the wind speed is about 5 kilometers per second.
“These winds are much faster than our jet stream, and are likely to carry clouds across the planet in about 20 hours,” said Daylan, who has led previous work on the planet using NASA’s MESS-led TESS mission.
Astronomers have reserved time on the James Webb Space Telescope to observe WASP-121b later this year and hope to map changes not only in water vapor but also carbon monoxide, which scientists believe should be in the atmosphere.
“This would be the first time we could measure a molecule containing carbon in the planet’s atmosphere,” says Michal-Evans. “The amount of carbon and oxygen in the atmosphere gives clues as to where such planets are formed.”
Thomas Michal-Evans, Diurnal variations in the stratosphere of the superheated giant exoplanet WASP-121b, Astronomy of nature (2022). DOI: 10.1038 / s41550-021-01592-w. www.nature.com/articles/s41550-021-01592-w
Citation: The Dark Side of “Hot Jupiter” is revealed in detail for the first time (2022, February 21), obtained on February 21, 2022 from https://phys.org/news/2022-02-hot-jupiter-dark-side-revealed. html
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