Helium found in an exoplanet's atmosphere for the first time

Though scientists long theorized they would find helium in exoplanets' atmospheres, it was never previously detected.
By Laurel Kornfeld | May 03, 2018
An international team of astronomers has detected helium in the atmosphere of a planet beyond our solar system for the first time.

Using the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3), the researchers found helium in the atmosphere of exoplanet WASP-107b, a low-density, Jupiter-sized planet that has only 12 percent Jupiter's mass, is approximately 200 light years from Earth, and orbits its star once every six days.

The scientists found the helium by analyzing the infrared spectrum of the planet's extended atmosphere when it passed in front of its parent star.

Previous studies of exoplanets' atmospheres was done by analyzing their spectra at optical and ultraviolet wavelengths.

As a planet transits in front of its star, a very small amount of the star's light passes through the planet's atmosphere, leaving a telltale fingerprint scientists can detect in the star's spectrum.

"Helium is the second-most common element in the universe after hydrogen. It is also one of the main constituents of the planets Jupiter and Saturn in our solar system. However, up until now, helium had not been detected on exoplanets--despite searches for it," said Jessica Spake of the University of Exeter in the UK, who led the study.

"The strong signal from helium we measured demonstrates a new technique to study upper layers of exoplanet atmospheres in a wider range of planets. Current methods, which use ultraviolet light, are limited to the closest exoplanets. We know there is helium in the Earth's upper atmosphere, and this new technique may help us to detect atmospheres around Earth-sized exoplanets--which is very difficult with current technology," she explained.

WASP-107b's atmosphere was found to have such an abundance of helium that scientists believe it extends thousands of miles into space. The parent star, WASP-107b, is very active, a phenomenon that causes atmospheric loss. Stellar radiation is absorbed by the planet's atmosphere, which then heats up, causing the latter to expand and escape.

Researchers are confident that this new method of studying planets' atmospheres, especially when combined with more sophisticated instruments, such as the James Webb Space Telescope (JWST), will reveal their atmospheres in a higher level of detail.

A paper on the findings has been published in the journal Nature.


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