Hubble Telescope Detects Helium In Atmosphere Of Exoplanet WASP-107b

Mindy Sparks
May 3, 2018

The amount of helium detected in the atmosphere of WASP-107b is so large that its upper atmosphere must extend tens of thousands of kilometres out into space. Helium has always been thought to be a byproduct of planets close enough into their stars that they lose parts of their atmosphere, and helium is common across our solar system - but it hadn't been seen on an exoplanet until now. 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.

The worldwide team of astronomers, led by Jessica Spake, a PhD student at the University of Exeter in the United Kingdom, used Hubble's Wide Field Camera 3 to discover helium in the atmosphere of the exoplanet WASP-107b This is the first detection of its kind. It's also common in gas-giant planets such as Jupiter and Saturn, and theorists have predicted that it should be detectable in exoplanet atmospheres.

Aside from the Hubble Space Telescope, astronomers might have another valuable resource available in the next few years for analyzing the atmosphere of exoplanets like WASP-107b. The discovery demonstrates the ability to use infrared spectra to study exoplanet extended atmospheres. It also has one of the cooler atmospheres compared to most exoplanets although it's still a blistering 500 degrees Celsius.

According to a news release published by the European Space Agency, the multinational team made the discovery with Hubble's Wide Field Camera 3, using the instrument to detect helium in WASP-107b's atmosphere.

WASP-107b is one of the lowest density planets known: While the planet is about the same size as Jupiter, it has only 12% of Jupiter's mass. "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". This also makes it the first time that an extended atmosphere has been discovered at infrared wavelengths. "This observation is going to open floodgates to a new area of exoplanet research, just because the helium signature is so strong", says Sara Seager, an astrophysicist and planetary scientist at the Massachusetts Institute of Technology in Cambridge who was a co-author of the 2000 prediction.

[1] The measurement of an exoplanet's atmosphere is performed when the planet passes in front of its host star. As soon as they downloaded the data, they saw an enormous spike in the star's light spectrum, at the near-infrared wavelength of 1.08 micrometres. The larger the amount of an element present in the atmosphere, the easier the detection becomes. The star's radiation is so powerful that models suggest the planet's atmosphere is actually eroding a tiny bit each year, perhaps forming a comet-like tail of helium. The star WASP-107 is highly active, supporting the atmospheric loss.

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