Distance from Saturn:
1.3 billion kilometers
(800 million miles)
This set of images (taken over three consecutive days) makes for some fun detective work and provides another great example of how scientists fuse together data from different sources to develop a greater understanding of cause and effect. For two reasons, the images have an odd quality about them. First, they combine ultraviolet (shown as white wisps surrounding Saturn’s south pole) with visible wavelength images of Saturn and its rings. The wisps show auroras that result when charged particles interact with the planet’s magnetic field. Just like the aurora borealis (or northern lights) that we occasionally see here on Earth, Saturn produces spectacular auroras in its south polar region when the solar wind slams into the magnetic field that surrounds the giant planet.
Secondly, the date and resolution of the images hint at something unusual. Note the date on which they were taken. Cassini had already been placed into orbit around Saturn where it continues to deliver much more detailed images of the rings and atmosphere. Instead, these images show a distant Saturn with little definition of the rings other than the familiar Cassini division. The reason? The distant images were actually taken by the Hubble Space Telescope which remains in a low Earth orbit.
Look closely and you’ll notice that the aurora brightened after the first day. Combining the Hubble imagery with data collected by Cassini let scientists measure the solar wind approaching Saturn and the radio emissions given off from the planet. Using the Hubble imagery with the Cassini measurements, they confirmed that the strong brightening of the aurora on January 26th corresponded with the recent arrival of a large disturbance in the solar wind.
For more details about the mission, please visit the NASA website.
Cassini has several instruments that help scientists understand the magnetic fields, charged particles and radiation emitted from Saturn. Unlike clouds, rings and moons, these attributes of Saturn are invisible to the human senses and must be measured directly.
 |  | The Cassini Plasma Spectrometer (CAPS) measures the energy and electrical charge of particles such as electrons and protons that the instrument encounters as well as the solar wind within Saturn's magnetosphere. |
 | | The Magnetospheric Imaging Instrument (MIMI) also produces images and other data about the particles trapped in Saturn's magnetic field including radiation emitted by the planet. |
 | | The Radio and Plasma Wave Science instrument (RPWS) measures the radio signals coming from Saturn, including the radio waves given off by the interaction of the solar wind with Saturn and Titan. |
