Spaceflight Insider

Cassini image shows Saturn heading toward solstice

Saturn's short shadow

The projection of Saturn’s shadow on the rings grows shorter as Saturn’s season advances toward northern summer, thanks to the planet’s permanent tilt as it orbits the Sun, as seen by NASA’s Cassini spacecraft. Image & Caption Credit: NASA / JPL-Caltech / Space Science Institute

A visible-light image of Saturn and one side of its rings taken by NASA’s Cassini spacecraft on February 3, 2017, shows the planet’s shrinking shadow on the rings as it approaches its May 2017 solstice.

Looking to the sunlit side of the rings from a position approximately 10 degrees above the ring plane, the image was captured by Cassini’s wide-angle camera.

It was taken from a distance of about 760,000 miles (1.2 kilometers) from the giant planet, with an image scale of 46 miles (73 kilometers) per pixel.

Saturn’s changing seasons as it progresses in its nearly 30-year solar orbit can be seen in images taken by the probe since it began orbiting the planet in July 2004.

Saturn Ringworld Waiting

Saturn’s peaceful beauty invites the Cassini spacecraft for a closer look in this natural color view, taken during the spacecraft’s approach to the planet. By this point in the approach sequence, Saturn was large enough that two narrow-angle camera images were required to capture an end-to-end view of the planet, its delicate rings and several of its icy moons. The composite is made entire from these two images. Image & Caption Credit: NASA / JPL / Space Science Institute

Shadows of the planet on the rings grew longer from Cassini’s 2004 arrival through its equinox in August 2009, when they subsequently began to shrink.

An image taken by Cassini in 2015 shows shorter shadows than those taken in 2009.

Saturn: The Rite of Spring

Of the countless equinoxes Saturn has seen since the birth of the Solar System, this one, captured here in a mosaic of light and dark, is the first witnessed up close by an emissary from Earth … none other than our faithful robotic explorer, Cassini. Image & Caption Credit: NASA / JPL / Space Science Institute

In the recent photo, the shadows are even shorter, stretching only to the innermost A ring. Images captured in earlier years show longer shadows extending to the middle and even outer A ring.

Seasons on Saturn, like those on Earth, are caused by the planet’s axial tilt, which, at 26.7 degrees, is slightly greater than that of Earth, which is 23.4 degrees.

Saturn's shadow barely bisected rings

Saturn’s shadow stretched beyond the edge of its rings for many years after Cassini first arrived at Saturn, casting an ever-lengthening shadow that reached its maximum extent at the planet’s 2009 equinox. This image captured the moment in 2015 when the shrinking shadow just barely reached across the entire main ring system. The shadow will continue to shrink until the planet’s northern summer solstice, at which point it will once again start lengthening across the rings, reaching across them in 2019. Image & Caption Credit: NASA / JPL-Caltech / Space Science Institute



Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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