A beautiful image of Saturn, the ringed wonderful planet
Credit: NASA/JPL/Space Science Institute

NASA recently published a wonderful image of Saturn, acquired by the Saturn-orbiting Cassini spacecraft. The image shows that the shadow of Saturn's rings, cast on the cloud tops of the giant planet, grew wider than in earlier images, taken in Summer 2009, due to Saturn’s orbital motion.

Like Earth, whose axial tilt of approximately 23.5 degrees gives rise to the four seasons, Saturn has seasons, as its axial tilt is about 27 degrees. However, Saturn’s seasons are much longer than Earth’s, since Saturn orbits the Sun every 30 years, approximately. Spring began in Saturn’s northern hemisphere in August 2009, when Sun’s rays were falling directly on the plane of the rings, which lies in the plane of Saturn’s equator. Therefore, the shadow of the rings was very thin. When spring or autumn begins, a planet is said to have passed a point in its orbit, termed the equinox. Saturn is now moving, along its orbit, away from its recent equinox.

For comparison, please access the link below, featuring a view of Saturn, with only a narrow shadow cast by the rings.
http://photojournal.jpl.nasa.gov/catalog/PIA11667

Intriguingly, as Saturn’s rings lie in the plane of the planet’s equator, to an Earth-based observer, the rings’ tilt to the line of sight varies over Saturn’s year, yielding various aspects of the rings.

In the above image, Saturn shows less detail, due to overexposure, but the brightness of the fainter rings has been enhanced. Pandora, a small Saturnian moon, is visible below the rings, to the left. Its brightness has also been increased, applying image processing.

The Cassini spacecraft was looking on the southern, dark side of the rings, from about 7 degrees below the ringplane. The image was taken in visual light, with Cassini’s wide-angle camera, on 24 June 2010. The spacecraft was at a distance of approximately 2.1 million km from Saturn.

The Cassini spacecraft was launched toward Saturn in October 1997. It has voyaged in interplanetary space for about seven years, to reach Saturn, in July 2004. Cassini has orbited Saturn more than 125 times, and acquired over 210,000 images of the planet and its bizarre moons. It is expected that Cassini’s mission will continue till 2017.

Further Reading

Cassini Mission Homepage
http://saturn.jpl.nasa.gov/

Aymen Mohamed Ibrahem
Senior Astronomy Specialist