The giant who melted

HD 209458bNASA’s Hubble Space Telescope makes an astonishing discovery while observing one of the first planets discovered beyond Earth’s solar system. The gas giant planet designated HD 209458b, orbiting the star HD 209458 in the constellation of Pegasus, 150 light years from Earth, is losing its atmosphere. Slightly larger than Jupiter, but locked into a dizzyingly tight orbit around its star (only 4,000,000 miles, with its “year” lasting less than half of an Earth week), HD 209458b’s atmosphere is boiling away into space thanks to the heat of the nearby star. This leads to a new exoplanet classification, “Hot Jupiters,” used to describe gas giants in similarly suicidal orbits. The core of HD 209458b will probably not last long once the last remnants of its atmosphere dissipate.