Shape-Shifting Asteroid with a Comet-like Tail

Active asteroids blur the distinction between asteroids and comets. Like other asteroids, they orbit the Sun in a belt between Mars and Jupiter. But they can also “shape shift," unfurling spectacular comet-like tails, then packing them away again. Observations of P/2017 S5 made with the WIYN telescope identify it as a water-bearing active asteroid and a step toward understanding the origin of water on Earth. The study was carried out by a team led by D. Jewitt (UCLA) that includes NOAO astronomers Jayadev Rajagopal, Susan Ridgway, and Wilson Liu.