The temperature on the nightsides of some hot Jupiters is surprisingly uniform, which suggests the dark sides have clouds made of minerals and rocks.
Hot Jupiters are massive gaseous planets similar in size to Jupiter, but orbiting other stars.
Using data from the Spitzer Space and the Hubble Space telescopes, the researchers from the McGill Space Institute found that the nightside temperature of 12 hot Jupiters they studied was about 800 degrees Celsius (1,472 degrees Fahrenheit).
Unlike our familiar planet Jupiter, so-called hot Jupiters circle very close to their host star — so close that it typically takes fewer than three days to complete an orbit. 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.