An artist's impression of a hypothetical exomoon in orbit around a planet in another planetary system. Dan Durda
Forget Exoplanets: The Hunt for Exomoons Is Heating Up
The universe seems almost infinitely reductive: our galaxy rotates around a central hub, planets orbit their planet stars, moons orbit their parent planets, and the odd moonlet may even orbit a moon.
Almost from the moment astronomers began finding planets around distant stars, they thus began talking about the moons that might orbit those alien worlds. It wasn't that they had any hope of discovering something as tiny as a moon: the smallest things they could find at the time were giant planets like Jupiter. But if a Jupiter happened to orbit in its star's Goldilocks Zone, where temperatures were relatively balmy, and if that Jupiter happened to have a moon about the size of Earth — not impossible, surely — then that hypothetical moon might have a chance of harboring life. That's a lot of ifs, which made talk of so-called exomoons seem like more of a marketing gimmick designed to gin up public interest in exoplanet science than a serious area of research.
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