An unusual, methane-free world is partially eclipsed by its star in this artist's concept. NASA's Spitzer Space Telescope has found evidence that a hot, Neptune-sized planet orbiting a star beyond our sun lacks methane -- an ingredient common to many planets in our own solar system.
Models of planetary atmospheres indicate that any world with the common mix of hydrogen, carbon and oxygen, and a temperature up to 1,000 Kelvin (1,340 degrees Fahrenheit) should have a large amount of methane and a small amount of carbon monoxide.
The planet illustrated here, called GJ 436b is about 800 Kelvin (or 980 degrees Fahrenheit) - it was expected to have methane but Spitzer's observations showed it does not.
The finding demonstrates the diversity of exoplanets, and indicates that models of exoplanetary atmospheres need to be revised.
Credit: NASA/JPL-Caltech› Larger image