The temperature of the dark side of hot Jupiter-type exoplanets is surprisingly uniform, according to the work of scientists at the McGill Space Institute.
PhD student in physics Dylan Keating and Professor Nicolas Cowan believe that this new knowledge, based on data collected by space telescopes Spitzer and Hubble, suggests that these giant gas planets have clouds made of minerals and even rocks.
The researchers measured a temperature of about 800 ° C on the surface of the dark face of twelve stars they probed.
The hot Jupiterian exoplanets are characterized by an illuminated hemisphere constantly turned towards their star and a dark face permanently immersed in the dark, a bit like the relationship between the Earth and the Moon.
Scientists had already measured significantly higher temperatures on the unlit side of hot Jupiterian planets, presumably due to energy transfers from one hemisphere to another.
Atmospheric circulation models predicted much more pronounced temperature variations on the dark sides.
Considering that the planets we observed were irradiated to varying degrees by their host star, and that temperature differences of nearly 1700 ° C were noted between their diurnal faces, these results are very surprising , says Dylan Keating.
According to astronomer Dylan Keating, the temperatures on the dark side are probably attributable to vaporized rock condensation, which occurs in these very hot atmospheres.
The recorded uniformity suggests that the clouds present on this side have a similar composition. Our data indicates that they are probably made up of minerals such as manganese sulphide and silicates, that is, rocks.
- On October 6, 1995, the Swiss scientists Michel Mayor and Didier Queloz of the Geneva Observatory announced the discovery of 51 Pegasi b, the first exoplanet detected to orbit a solar-type star.
- This planet, located about 50 light-years from Earth in the constellation Pegasus, is also hot Jupiter type.
- Since that time, astrophysicists have identified as many as 4043 exoplanets, and 4014 others are being confirmed.
- Of this number, 1267 are gas giants.
Head in the clouds
The researcher states that the basic physical principles behind cloud formation are invariable, and that studying those enveloping the dark side of hot Jupiterian planets could teach us more about the process elsewhere in the Universe, but also on Earth.
The future missions of the James-Webb or ARIEL telescopes could better define the composition and the mode of formation of these clouds, and perfect atmospheric circulation models on these planets.
By observing hot Jupiter at shorter and longer wavelengths, we will be able to characterize the clouds of their dark side.
The details of these works are published in the journal Nature).
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