Helium discovered in exoplanet atmosphere for the first time
An international team of astronomers has made the first-ever detection of helium in the atmosphere of an extrasolar world. The new technique used to make the discovery could pave the way for scientists hoping to reveal the atmospheres of distant Earth-sized exoplanets.
The planet at the heart of the new research is located roughly 200 light-years from Earth, in the constellation Virgo. Whilst the imaginatively-named WASP-107b is roughly comparable in size to Jupiter, it boasts only 12 percent of the gas giant's mass.
WASP-107b also has one of the chilliest atmospheres ever discovered shrouding a distant exoplanet, though, to put this in context, it's still about 500 °C (932 °F) hotter than the protective envelope of gas shrouding our own blue marble.
It is in the gaseous envelope of this unusual exoplanet that astronomers have made the first discovery of helium existing in the atmosphere of a world outside of our solar system.
Helium, for context, is pretty great. Alongside filling party balloons, it just so happens to be the second most abundant element in the known universe. In our solar system, the element is created in vast quantities as a result of the nuclear fusion process occurring at the heart of the Sun, and is present in massive quantities in the planets that inhabit our neck of the cosmic woods.
Astronomers have long predicted that the atmospheres of distant worlds like WASP-107b would also play host to significant quantities of helium, however, the element had not been detected in the gaseous shells surrounding these far-off worlds until now.
The team behind the discovery used the observational prowess of the venerable Hubble Space Telescope to probe WASP-107b, measuring the spectrum of light that had passed through the upper reaches of the exoplanet's atmosphere.
The researchers employed a new technique to analyse the data, which measured the infrared properties of the atmospheric light to detect helium that existed in an excited state. The method pioneered by the researchers does not rely on collecting ultraviolet light data, which is the conventional medium of probing exoplanet atmospheres.
An analysis of the Hubble data revealed a strong helium signature, which led the astronomers to conclude that WASP-107b's was surrounded by a tenuous atmospheric cloud that reached tens of thousands of kilometers into space.
The team believe that their infrared-based technique could be used to detect similar hydrogen-rich atmospheres that exist around smaller Earth-sized exoplanets located very far from Earth.
"We hope to use this technique with the upcoming James Webb Space Telescope (JWST), 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," comments Jessica Spake, of Exeter University's Physics and Astronomy. "By measuring infrared light, we can see further out into space than if we were using ultraviolet light."
The launch of the JWST was recently delayed once again, and is now expected no earlier than May 2020. Once finally operational, the JWST will boast numerous benefits over existing orbital telescopes, including a higher spectral resolution, greater sensitivity, and longer uninterrupted observation times.
The capabilities of next generation telescopes such as the JWST, and planet hunting satellites such as the recently launched Transiting Exoplanet Survey Satellite, herald the beginning of an exciting new age for the discovery and characterization of distant worlds.
A paper detailing the new discovery is set to be published in the journal Nature on May 3.
Source: Exeter University