For the first time, researchers have been able to observe the atmosphere of a planet between the sizes of Earth and Neptune. Gliese 3470 b is a world 96 light-years away, orbiting a star roughly half the size of the Sun. It is 12.6 times the mass of our planet and slightly smaller than Neptune, which weighs 17 times the mass of the Earth.
As reported in Nature Astronomy, this planet delivered quite the surprise to astronomers. Using the combined power of the Hubble Space Telescope and NASA’s Spitzer infrared observatory, they discovered a clear atmosphere of hydrogen and helium, the main components of stars.
“We expected an atmosphere strongly enriched in heavier elements like oxygen and carbon which are forming abundant water vapor and methane gas, similar to what we see on Neptune,” lead author Björn Benneke, of the University of Montreal, said in a statement. “Instead, we found an atmosphere that is so poor in heavy elements that its composition resembles the hydrogen/helium-rich composition of the Sun.”
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