Kepler 1780-b is a gas giant exoplanet orbiting the F-type star Kepler 1708, some 5500 light-years from Earth. Orbiting at a distance of 1.64 astronomical units from its star, the planet has a mass of 4.6 times that of Jupiter but is estimated to be smaller in size. In 2021, astronomers announced the likely detection of not only the planet (yellow), but a super-sized satellite orbit in around it (green), dubbed Kepler 1701-b-i. Unlike the satellites of the Solar System's planets, the 'exomoon' is not rocky - it's gaseous, somewhat similar to the planet Neptune. Thousands of exoplanets are now known, but exomoons - although most certainly common - have mostly evaded discovery until now, because it presents a much more difficult challenge.