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...