Observing alien Saturns

Shreyas Vissapragada, a planetary astronomer at Caltech, started thinking about the possibility of super-puffs being ringed planets after another astronomer asked him about it.



“If an alien observed Saturn with the Kepler space telescope, how badly would they get the density wrong if they didn't realize it had rings?” Vissapragada said he asked himself. He did the math and found that they might calculate Saturn’s density to be only half of what it really is.



He teamed up with Anthony Piro, an astronomer at the Carnegie Institution for Science, to investigate what this could mean for Earth astronomers’ observations.



The pair considered what the ring systems would have to be like for known super-puffs to be ringed planets. For example, most known super-puffs are fairly close to their stars, so their rings would have to be rocky rather than icy. Some of the planets wouldn’t be able to have rocky rings wide enough to throw off density estimates, because rocky material that's too far from the planet would clump to form moons. For other super-puffs, rings might still be a possibility.