This is a moon that orbits a planet found outside our solar system. Planets that orbit stars other than our sun, such as Alpha Centauri, are known as exoplanets. If those exoplanets have moons that orbit them? Those are exomoons.
Scientists have not yet confirmed that exomoons exist. But they’ve got some evidence from powerful space telescopes such as Hubble and Kepler. These telescopes have spotted dips in light in front of stars. That dimming is what happens when an exoplanet passes in front of the star. But sometimes, that dip is followed by a second dimming. That could be the exoplanet’s exomoon, trailing along behind.
In a sentence
When exoplanets are too hot or cold to support life, scientists might look to their exomoons for aliens instead.