Primitive atmosphere surrounds 'Warm Neptune,' astronomers confirm

May 11 (UPI) -- Astronomers have discovered a primitive atmosphere surrounding a "Warm Neptune" exoplanet, a Neptune-like world orbiting closer to its host star.

The discovery, detailed in the journal Science, may help researchers better understand how planets form and evolve in distant solar systems.

"This 'Warm Neptune' is a much smaller planet than those we have been able to characterize in depth, so this new discovery about its atmosphere feels like a big breakthrough in our pursuit to learn more about how solar systems are formed, and how it compares to our own," David Sing, an astronomer at the University of Exeter, said in a news release.

Researchers were able to observe the Warm Neptune's atmosphere is the exoplanet passed across the face of its host star, located some 430 light years from Earth.

Based on the wavelengths absorbed by the exoplanet's atmospheres, research suggests the alien world, dubbed HAT-P-26b, is surrounded by a combination of hydrogen and helium. The data, collected by both the Hubble Space Telescope and NASA's Spitzer Space Telescope, suggest the atmosphere is without clouds and hosts strong water vapor signatures.

The Warm Neptune's atmosphere either formed close to its host star or late in the evolution of the star's protoplanetary disk -- or both.

Ice giants like our own solar system's Uranus and Neptune host higher concentrations of metallic elements because they formed along the outskirts of the sun's protoplanetary disk. Early on, they were bombarded by icy debris rich in heavier elements.

But though HAT-P-26b is roughly the same size as Neptune, it is closer in metallicity to Jupiter and formed closer to its host star -- it's an anomaly.

"Astronomers have just begun to investigate the atmospheres of these distant Neptune-mass planets, and almost right away, we found an example that goes against the trend in our solar system," said NASA scientist Hannah Wakeford. "This kind of unexpected result is why I really love exploring the atmospheres of alien planets."