Work bySara Seager and colleagues with NASA’s Spitzer Space Telescope generated press last week for reporting the first measurements of day and night temperatures of a planet outside our solar system. According to the Spitzer Space Telescope release, the infrared observatory revealed that the Jupiter-like gas planet, circling very close to its star, is always extremely hot on one side and as cold as ice on the other. Previous studies of extrasolar planets have described only whole-globe traits such as size and mass.

The gas giant planet, Upsilon Andromeda b, is a so-called “hot-Jupiter.” It circles closely around its star every 4.6 days. Seager and her colleagues determined that the temperature variation between the planet’s light and dark sides is about 2,550 degrees Fahrenheit.

Seager commented in the Carnegie Press Release, “The observation completely changes our thinking about hot gas giant exoplanets. Most astronomers expected them to be more uniformly heated, much like Jupiter. But this planet clearly has a hot side and a cool side.”

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