Researchers think observations from the Hubble Space Telescope might be our first evidence of an exomoon, or “a moon orbiting a planet outside our solar system,” according to the American Association for the Advancement of Science. Exoplanet sightings have become frequent in the past few years, particularly after NASA’s Kepler telescope spent years hunting for transiting planets, a technique used by planet hunters to prove the existence of a planet by spotting their shadows pass in front of a star. The team’s research seems to show that Kepler-1625b, a “Jupiter-sized” planet, might have an exomoon, based on 40 hours of observation of transiting planets using the Hubble Space Telescope, considered four times more precise than Kepler. Besides shadows and gravitational changes, the team found that there was a dimming “trailing the planet like a dog following its owner on a leash,” according to a press release. While researchers are almost positive their work shows proof of an exomoon, they cautioned their results were preliminary and would require confirmation with more observations and work; the dimming and trailing could be proof of another exoplanet.