* Astronomy

Photogenic Saturn has now become a movie star. Astronomers have woven NASA Hubble Space Telescope images of Saturn, its rings, and several of its moons into three movies. Each movie highlights unique times in the planet's 30-year waltz around the Sun. Two of the movies show the motion of several of Saturn's moons when the planet's rings were tilted nearly edge-on to Earth and to the Sun. These edge-on alignments of the rings occur roughly once every 15 years. Another movie presents a clear view of Saturn's Southern Hemisphere when the planet's rings were at maximum tilt toward Earth. Hubble snapped only about a dozen images during each of these three events, so astronomers created software to extend the photos into the hundreds of images needed for a movie. The images were taken with Hubble's Wide Field and Planetary Camera 2 in 1995 and the Advanced Camera for Surveys in 2003



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This image was taken by the Cassini spaceprobe on February 04, 2007, when it was approximately 1,198,741 kilometres away.


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Credit NASA

The image was taken using the CB2 and IRP90 filters.

This image of Saturn was taken by the Cassini spaceprobe on February 01, 2007, when it was approximately 888,709 kilometres away.


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Credit NASA

The image was taken using the MT3 and CL2 filters.

UK researchers from University College London (UCL), along with colleagues from Boston University, have found that the hotter than expected temperature of Saturn’s upper atmosphere – and that of the other giant planets – is not due to the same mechanism that heats the atmosphere around the Earth’s Northern Lights. Reporting in Nature (25th January) the researchers findings thus rule out a long held theory.
A simple calculation to give the expected temperature of a planet’s upper atmosphere balances the amount of sunlight absorbed by the energy lost to the lower atmosphere. But the calculated values don’t tally with the actual observations of the Gas Giants: they are consistently much hotter.
It has long been thought that the culprit behind the heating process was the ionosphere, being driven by the planet’s magnetic field, or magnetosphere. By using numerical models of Saturn’s atmosphere the researchers found that the net effects of the winds driven by polar energy inputs is not to heat the atmosphere but to actually cool it.

"The aurora has been studied for over a hundred years, yet our discovery takes us back to first principles. We need to re-examine our basic assumptions about planetary atmospheres and what causes the observed heating. Studying what happens on planets such as Saturn gives us an insight into what happens closer to home. Planets can lose their atmospheres as we see with Mars. Do we completely understand how this happens? Are there mechanisms heating the gas and causing it to escape that we do not yet fully understand? By studying what happens in other atmospheres we may find clues to Earth’s future" - Professor Alan Aylward, of the UCL Department of Physics & Astronomy, and an author of the study.

The study was funded by the UK Particle Physics and Astronomy Research Council (PPARC) and Sun Microsystems Ltd and carried out using the HiPerSPACE facility at University College London.