Saturn’s moon Dione crosses the face of the giant planet in this view, a phenomenon astronomers call a transit. Transits play an important role in astronomy and can be used to study the orbits of planets and their atmospheres, both in our solar system and in others.
By carefully timing and observing transits in the Saturn system, like that of Dione (698 miles or 1123 kilometres across), scientists can more precisely determine the orbital parameters of Saturn’s moons.
This view looks toward the unilluminated side of the rings from about 0.3 degrees below the ring plane. The image was taken in visible green light with NASA’s Cassini spacecraft’s narrow-angle camera on 21 May 2015.
The view was acquired at a distance of approximately 1.4 million miles (2.3 million kilometres) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 119 degrees. Image scale is 9 miles (14 kilometres) per pixel.