This diagram illustrates how hypothetical helium atmospheres might form. These would be on planets about the mass of Neptune, or smaller, which orbit tightly to their stars, whipping around in just days. Image credit: NASA/JPL-Caltech › Full image and caption
They wouldn't float like balloons or give you the chance to talk in high, squeaky voices, but planets with helium skies may constitute an exotic planetary class in our Milky Way galaxy. Researchers using data from NASA's Spitzer Space Telescope propose that warm Neptune-size planets with clouds of helium may be strewn about the galaxy by the thousands.
"We don't have any planets like this in our own solar system," said Renyu Hu, NASA Hubble Fellow at the agency's Jet Propulsion Laboratory in Pasadena, California, and lead author of a new study on the findings accepted for publication in the Astrophysical Journal. "But we think planets with helium atmospheres could be common around other stars."
Jet Propulsion Laboratory, Pasadena, California