Astronomy Picture of the Day

Explanation: Don’t get spooked by Saturn’s ghostly spokes! Today we feature a nearly two-hour timelapse of Saturn and its rings looping forwards and backwards. If you look closely, a ghoulish shadow appears and disappears as  Saturn’s B ring  rotates. Decades of observation with  Voyager 2,  Cassini, and Hubble  show the appearance of Saturn’s spokes varies with  the planet’s seasons. Like Earth, Saturn’s  spin axis  is tilted compared to the plane of its orbit around the Sun. During Saturn’s  equinox, the rings are  less tilted  toward the Sun and they receive sunlight at a shallower angle. Saturn’s spokes may be electrically charged dust and ice temporarily levitated above the rings by electromagnetic forces. It is still uncertain, but the ring plasma and charge environment may be influenced by changing ultraviolet illumination, meteoroid impacts, or indirect effects from interactions between the solar wind and the planet’s magnetic field.