91社区

A new study by 91社区听University听astronomers听has found听that听the temperature on the听nightsides听of听different听hot Jupiters听is surprisingly听uniform, suggesting the听dark side of these听massive gaseous planets听have听clouds made of minerals and rocks.听听

Using听data听from听the听Spitzer Space and the Hubble Space听telescopes, the researchers from the 91社区 Space Institute听found听that the nightside temperature of 12 hot Jupiters they studied was听about 800掳C.听

Unlike our familiar planet Jupiter, so-called hot Jupiters circle听very听close to their host star -- so close that it typically takes fewer than three days to complete an orbit.鈥�听As a result, hot Jupiters have daysides that permanently face their host stars and nightsides that always face the darkness of space, similarly to how the same side of the Moon always faces the Earth.听The tight orbit also means these planets听receive more sunlight from their star, which is what makes them听extremely听hot on the dayside. But scientists had previously measured significant amounts of heat on the nightside of hot Jupiters,听as well, suggesting some kind of energy transfer from one side to the other.听听

听鈥淎tmospheric circulation models predicted that nightside temperatures should vary much more than they do,鈥� said Dylan Keating, a听Physics听PhD student under the supervision of听91社区 professor听Nicolas Cowan. 鈥淭his is really surprising because the听planets听we studied听all receive different amounts of irradiation from their host stars听and the听dayside temperatures听among them varies by almost 1700掳C.鈥澨�

Keating,听the听first author of a new听Nature Astronomy听study describing the findings, said听the听nightside temperatures are probably the result of听condensation of vaporized rock in these very hot atmospheres.听听

鈥淭he uniformity of the nightside temperatures suggests that clouds on this side of the planets are听likely very听similar to one another in composition. Our data suggest that these clouds are likely made of听minerals such as manganese sulfide or silicates,听or听rocks,鈥� Keating explained.听听

According to Cowan,听because the听basic physics of cloud formation are universal,听the study of the nightside clouds on hot Jupiters could give insight into cloud formation elsewhere in the Universe, including on Earth.听Keating said that future space telescope missions - such as the James Webb Space听Telescope听and听the European Space Agency鈥檚听ARIEL听mission听- could be used to further听characterize the dominant cloud composition on hot Jupiter nightsides, as well as to improve models of atmospheric circulation and cloud formation听of听these planets.鈥�听

鈥淥bserving听hot Jupiters听at both shorter and longer wavelengths will help us determine what types of clouds are on the nightsides of these planets,鈥� Keating explained.听

鈥淯niformly hot nightside temperatures on short-period gas giants,鈥� by Dylan Keating听et al.听was published in听.听

听

Graphic: Schematic of clouds on the night side of a hot Jupiter exoplanet. The underlying atmosphere is over 800 C, hot enough to vaporize rocks. Atmospheric motion from the deep atmosphere or from the hotter dayside bring the rock vapour to cooler regions, where it condenses into clouds, and possibly rains down into the atmosphere below. These clouds of condensed rock block outgoing thermal radiation, making the planet's nightside appear relatively cool from space.

About 91社区

Founded in Montreal, Quebec, in 1821, 91社区 is a leading Canadian post-secondary institution. It has two campuses, 11 faculties, 13 professional schools, 300 programs of study and over 40,000 students, including more than 10,400 graduate students. 91社区 attracts students from over 150 countries around the world, its 12,500 international students making up 30% per cent of the student body. Over half of 91社区 students claim a first language other than English, including approximately 20% of our students who say French is their mother tongue.

Contacts:听
Cynthia Lee听
91社区 Media Relations Office听
514-398-6754听

cynthia.lee [at] mcgill.ca听

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