Hubble Spies Helium in an Exoplanet’s Atmosphere for the First Time

The Hubble Space Telescope has spied helium in the atmosphere of an exoplanet, WASP-107b, for the first time in history. WASP-107b is a very unusual planet. It’s roughly Jupiter-size (0.94RJ), but has just 1/8 of Jupiter’s mass. And by terrestrial metrics, it orbits practically on top of its host star, at 0.055 AU (or roughly 6 percent of the distance between the Earth and the Sun). Consequently, WASP-107b whips around its host star in a matter of days — presumably in a vast, ill-defined cloud of atmosphere. Finding helium around an exoplanet is a genuine first for astronomy since, despite being the second-most abundant element in the universe behind hydrogen, we hadn’t previously detected helium in the atmosphere of any planet orbiting a star.

The research team at the University of Exeter was led by Jessica Spake, who told Space.com, “This is a new method to probe the upper parts of an exoplanet atmosphere, where high-energy radiation is observed.” Her team’s observations of WASP-107b turned up evidence of helium in the atmosphere by focusing on measuring changes to WASP-107’s infrared light and how that light changed when passing through the atmosphere of WASP-107b. There’s no chance of the helium being produced by the star and mistakenly detected as being part of WASP-107b’s atmosphere — according to Spake, the detected signal of helium is more than 5x larger than what a star with the characteristics of WASP-107 would otherwise produce.

In fact, WASP-107b’s atmosphere is eroding so quickly, the entire planet may be wrapped in a comet-like tail of material. The atmospheric temperature is estimated at over 500C and the gravity of WASP-107b is undoubtedly quite low, given the planet’s low density.

The detection of exoplanet atmospheres is obviously of critical importance to our ongoing efforts to detect life elsewhere in the universe. Don’t mistake us — missions like Kepler’s have been critical to our search for intelligent life. But now that we know that planets exist and are plentiful around many stars, we need to know what kind of atmosphere those planets have. This type of investigation should get several boosts in the near-term future.

One of the primary missions of the James Webb Space Telescope will be to image the atmospheres around exoplanets; the diagram above shows the full spectrum range of the JWST compared with the Hubble. There are also plans to use the European Extremely Large Telescope (E-ELT) for examination of exoplanet atmospheres. While ground-based telescopes can’t use the ultraviolet spectrum like Hubble can for exoplanet atmosphere examination, they can make wider use of the same infrared bands that were ultimately used for these findings as well.

It’s only been a handful of years since we had firm confirmation that there were tens of billions of planets in the galaxy, as opposed to simply being theorized to exist. It won’t be too much longer before we’ll be able to characterize the atmospheres of exoplanets we didn’t even know existed.

Feature Image: ESA/Hubble, NASA, M. Kornmesser

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