To carry out their investigation of WASP-107b, the researchers used the Wide Field Camera 3 on the Hubble Space Telescope to view infrared light passing through the planet’s upper atmosphere. Then, by analyzing the light’s spectrum, the researchers were able to decode the elemental composition of the planet’s air, ultimately finding a great deal of helium in an excited state.The traditional method for studying exoplanetary atmospheres is to observe them in ultraviolet or optical light, which both have relatively high energies. However, this new study focused on infrared light, which has a much longer wavelength (and, therefore, lower energy) and passes directly through Earth’s atmosphere. Previous ultraviolet-based searches required orbiting space observatories to investigate the chemical makeup of an exoplanet’s atmosphere. But, by proving that infrared light can also be used, astronomers have shown that ground-based telescopes can help study the air around exoplanets, too.“The strong signal from helium we measured demonstrates a new technique to study upper layers of exoplanet atmosphere in a wider range of planets,” says Spake. “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.”Although future projects could use telescopes here on Earth to study exoplanets, the technique may be even more valuable for future space-based observatories. “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 Spake. “By measuring infrared light, we can see further out into space than if we were using ultraviolet light.”