A Helium Tail Trails This Fluffy Alien Planet

[Judi Lynn]

By Sarah Lewin, Space.com Associate Editor | December 6, 2018 02:00pm ET

As a Jupiter-size world swings around its small but active star, bombarded by radiation, the planet leaves behind a tail of escaping helium as wide as itself — and researchers have spotted this tail from the ground, 163 light-years away.

Since scientists first found planets around other stars, many of their most striking discoveries have come from off-Earth instruments like NASA’s Kepler and Hubble space telescopes. Kepler has identified more than 2,000 verified planets passing by their stars, while Hubble observations have helped scientists characterize exoplanet atmospheres. But two new papers published today (Dec. 6) in the journal Science pinpoint the movement of helium in alien atmospheres from the comfort of our home planet.

The two research teams both used a 3.5-meter (11 feet) telescope in Calar Alto, Spain, to make their measurements — taking advantage of the telescope's powerful CARMENES instrument (short for Calar Alto high- Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) to finely measure the action of helium surrounding the planets. [The Most Intriguing Alien Planet Discoveries of 2017]

"This is the first time we can actually observe a helium tail," Lisa Nortmann, lead author on one of the new papers and a researcher at Instituto de Astrofísica de Canarias (IAC) in Spain, told Space.com. In their new paper, Nortmann's group looked for helium in the outer atmospheres of multiple planets. And one, called WASP-69b, showed a particularly dramatic effect.

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