A new study suggests the dark sides of different ‘hot Jupiters’ are very similar. These giant gas planets could have clouds made of minerals and rocks.
Hot Jupiters are massive gaseous planets just like our own Jupiter, but much, much warmer. That’s because they orbit much closer to their host star than Jupiter does.
Astronomers from the McGill Space Institute used data from the Spitzer and Hubble Space Telescopes to study hot Jupiter exoplanets. Thus, they found that the nightside temperature of 12 hot Jupiters was about 800°C.
These particular planets are all tidally-locked. That means they have daysides that permanently face their parent stars and nightsides that always face the darkness of space. The tight orbit also makes their star-facing side extremely hot.
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But what about the side facing away from the star? That should be much colder right? Well, the research, published in Nature Astronomy, suggests the dark side temperatures of hot Jupiters are typically quite similar.
Scientists suggest some kind of energy transfers from dayside to the nightside.
“Atmospheric circulation models predicted that nightside temperatures should vary much more than they do,” said Dylan Keating, a Physics Ph.D. student under the supervision of McGill professor Nicolas Cowan. “This is really surprising because the planets we studied all receive different amounts of irradiation from their host stars and the dayside temperatures among them varies by almost 1700°C.”
Keating, the first author of a new Nature Astronomy study describing the findings, said the nightside temperatures are probably the result of condensation of vaporized rock in these very hot atmospheres.
Clouds there, form a thick blanket that blocks heat from radiating out into space where it can be detected. But these clouds are made of rock. The intense temperatures of the dayside vaporize these rocks and then wind brings them around to the dark side. There, colder temperatures make them condense into clouds, and possibly a rocky rainfall.
“The uniformity of the nightside temperatures suggests that clouds on this side of the planets are likely very similar to one another in composition. Our data suggest that these clouds are likely made of minerals such as manganese sulfide or silicates, or rocks,” Keating explained.
Furthermore, astronomers want to observe these hot Jupiters in different wavelengths. That will help them determine what these clouds actually are.
Researchers published their study in the journal Nature Astronomy.