A map of the day–night contrast of the extrasolar planet HD 189733b

'Hot Jupiters' just got hotter 'Hot Jupiter' extrasolar planets are close to their parent stars, so are likely to be tidally locked (like the Earth and Moon), with permanent day and night sides. That raises the question of whether the atmosphere is able to transport energy from the day side to the night side. Infrared data from the Spitzer Space Telescope have now answered that question for the extrasolar planet HD 189733b. Night and day temperatures are similar, around 950–1,200 K, indicating that energy from the irradiated side is efficiently redistributed throughout the atmosphere. A paper going live online this week reports observations of the atmosphere of the extra-solar plant HD 149026b. It’s a very hot Jupiter, the hottest planet known, at about 2,300 K. This matches predictions for a planet where each patch of surface area instantaneously re-emits all absorbed light as a blackbody. ‘Hot Jupiter’ extrasolar planets are expected to be tidally locked because they are close (