Hubble Spotted Helium in the atmosphere of a Comet-Like World

For the very first time, helium has been detected as a constituent of the atmosphere of an alien planet. This discovery indicates that it is viable to study the atmosphere of some exoplanets, without having to launch a space telescope for this purpose, according to researchers. 

According to Jessica Spake, the lead author of the study, this new method will help in probing the upper reaches of the atmosphere of an exoplanet, having high-energy content. 

To study a faraway planet’s atmosphere, researchers have to wait for this comet-like world to move between the Earth and that planet’s closest star. Since the planet will block a portion of the light emanating from the star, studying the light aids scientists to the conclusion about the planet’s atmosphere and its composition. However, this is a complicated process with only a few instances of success. The focus of the study had remained mostly on hydrogen, with helium remaining unseen until now. 

WASP-107B changed all of that. It is at a distance of 200 light years from our planet. Its diameter is similar to that of Jupiter but is one-eighth its mass. Hence it is highly low-density. At a scorching temperature of 500 degree Celsius, the atmosphere of this planet is hotter than most other exoplanets.

Using NASA's Hubble Space Telescope, Jessica Spake and colleagues observed the heated planet. They picked up on the infrared radiation. By studying the light that passes through the exoplanet’s atmosphere, the scientists could identify helium, that too in its wild form. Earlier measurements of the planet’s atmosphere made use of ultraviolet (UV) light, which the Earth's atmosphere usually blocks. However, infrared radiation can still pass through clouds and air. Thus ground-based telescopes can detect it.

Other than Hubble, James Webb Space Telescope by NASA (scheduled to be launched in 2020), costing a whopping 8.8 billion USD. This will be capable of making similar observations, as also will ground-based scopes such as the European Observatory's “Very Large Telescope” (Chile), and the “Keck telescopes” (Hawaii).  

WASP-107b is an apt subject for the new method since a vast quantity of its atmosphere is lost to the expanses of space. The scientists concluded that UV radiation from the planet’s star is thinning the planet's atmosphere, making it look like a comet-like tail. The method will let researchers study planets much farther away from the Earth’s sun that could be done in case of using UV radiation, according to Spake.