NASA's Cassini Probe Photographs Uranus from Saturn
NASA's Cassini probe, which has been studying Saturn for nearly a decade, turned away from the ringed planet for a moment last month, setting its sights on the planet's neighbor Uranus. The results were an image of the icy blue world in the distance beyond Saturn's rings.
In the image, Saturn's rings are clearly visible in the foreground and Uranus is the tiny blue dot in the upper left part of the frame.
At the time the image was taken on April 11, Uranus was nearly 29 astronomical units away from Cassini. One astronomical unit, about 93 million miles, is the distance between Earth and the Sun.
The closest the orbits of Saturn and Uranus ever get happens once about every 30 years, when the two planets approach within about 10 astronomical units of each other, according to NASA.
Uranus and its neighbor Neptune are sometimes referred to as the "ice giants" because of their blue hue.
"The moniker derives from the fact that a comparatively large part of the planets' composition consists of water, ammonia and methane, which are typically frozen as ices in the cold depths of the outer solar system," NASA said in a statement.
The so-called "gas giants," Jupiter and Saturn, are made almost entirely of hydrogen and helium, with smaller percentages of these ices.
In addition to being a out-of-this-world photo, the real-color image of Uranus beyond Saturn has some practical appeal as well.
"Scientists working on several of Cassini's science investigations expect that they will be able to use images and spectra from these observations to help calibrate their own instruments," NASA said.