Helium Detected in Exoplanet’s Atmosphere for First Time

The exoplanet WASP-107b is a gas giant, orbiting a highly active K-type main sequence star. The star is about 200 light-years from Earth. Using spectroscopy, scientists were able to find helium in the escaping atmosphere of the planet — the first detection of this element in the atmosphere of an exoplanet. (ESA/Hubble, NASA, M. Kornmesser)

(CN) – Helium has been detected in the atmosphere of a planet outside our solar system for the first time, a team of astronomers reported Tuesday.

Helium – the second most common element in the universe – has been predicted to be one of most easily detected gases on large exoplanets, which orbit a star other than the sun. It is also one of the main components of the gas giants Jupiter and Saturn.

But despite helium’s prevalence in the universe, detection of it on large exoplanets has eluded astronomers until now.

Detailed in a study published in the journal Nature, the groundbreaking discovery reveals a massive volume of helium in the upper atmosphere of the exoplanet WASP-107b. Discovered in 2017, WASP-107b is 200 light-years from Earth in the constellation Virgo.

The astronomers say their findings could pave the way for scientists to detect more atmospheres around the Milky Way’s Earth-sized exoplanets.

“We hope to use this technique with the upcoming James Webb Space Telescope, for example, to learn what kind of planets have large envelopes of hydrogen and helium, and how long planets can hold on to their atmospheres,” said lead author Jessica Spake, a doctoral student at the University of Exeter in the United Kingdom.

“By measuring infrared light, we can see further out into space than if we were using ultraviolet light.”

Orbiting its host star every six days, WASP-107b has one of the chilliest atmospheres of any known exoplanet. At 932 degrees Fahrenheit, however, it is significantly hotter than Earth.

And while similar in size to Jupiter, the very low-density exoplanet is just 12 percent of its mass.

By analyzing the spectrum of light passing through the upper portion of WASP-107b’s atmosphere, the team was able to detect helium in an excited state.

The considerable strength of the signal measured capitalized on a new technique that does not rely on ultraviolet measurements, which have traditionally been used to analyze upper atmospheres of exoplanets. The astronomers believe this new approach, which uses infrared light, could establish new paths to exploring the atmospheres of Earth-sized exoplanets across the universe.

“The helium we detected extends far out to space as a tenuous cloud surrounding the planet,” said co-author Tom Evans, a research fellow at the University of Exeter. “If smaller, Earth-sized planets have similar helium clouds, this new technique offers an exciting means to study their upper atmospheres in the very near future.”

The first evidence of helium occurred as an unknown yellow spectral line signature in 1868. British astronomer Norman Lockyer was the first to suggest the line was due to a new element and subsequently named it after Helios, the personification of the sun in Greek mythology.

The research was funded by NASA, Tennessee State University, the state of Tennessee’s Centers of Excellence program, and the David and Lucile Packard Fellowship for Science.

 

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