b'16 Carnegie Science|Fall 2020Do Cotton Candy Planets Sport Rings? S urprisingly, some super-puff,ringed planets orbiting distant stars.extremely low-density, cottonThe radii of exoplanets are measured candy-like exoplanets maywhen the exoplanet crosses in front of its actually have rings, accordinghost star causing a dip in the stars light. to new research from Carnegies AnthonyThe greater the size of the dip, the larger the Piro and Caltechs Shreyas Vissapragada. exoplanet.Super-puffs have exceptionally largeWe wondered, if you were to look back radii for their masseswhich would giveat us from a distant world, would you them incredibly low densities. Theserecognize Saturn as a ringed planet, or adorably named bodies have confoundedwould it appear to be a puffy planet to an scientists since they were first discovered:alien astronomer? Vissapragada asked. they are unlike any planets in our SolarTo test this hypothesis, Piro and System and challenge our ideas of whatVissapragada simulated how a ringed distant planets can be. exoplanet would look to an astronomer with We started thinking, what if thesehigh-precision instruments watching it planets arent airy like cotton candy at all,transit in front of its host star. They also Piro said. What if the super-puffs seeminvestigated the types of ring material that so large because they are actuallycould compose super-puffs. surrounded by rings? The work showed that rings could In our own Solar System, all of theexplain some, but not all, of the super-puffs gas and ice giant planets have rings, withthat NASAs Kepler mission has discovered. the most well-known example being theThese planets tend to orbit in close majestic rings of Saturn. But it has beenproximity to their host stars, meaning that difficult for astronomers to discoverthe rings would have to be rocky, rather than Staff member Anthony Piro is a theoretical astrophysicisticy, Piro explained. But rocky ring radii can at the Carnegie Observatories. Image courtesy Sandy Huffaker only be so big, unless the rock is very porous, so not every super-puff would fit these constraints. According to Piro and Vissapragada, three super-puffs are especially good candidates for ringsKepler-87 c, Kepler-177 c, and HIP 41378f.Follow-up observations to confirm this work wont be possible until NASAs James Webb Space Telescope launches, because existing land- and space-based telescopes lack the necessary precision. If some of the super-puffs are confirmed as having rings, astronomers would better understand how these planetary systems formed and evolved around their stars.SUPPORT:The National Science Foundation and a Paul & Daisy Soros Fellowship for New Americans supported this work. This image shows an artists conception of Piro and Vissapragadas model of a ringed planet transiting in front of its host star. They used these models to refine which of the known super-puffs could be explained by rings. Image courtesy Robin Dienel, Carnegie Institution for Science'