Waiting in the wings, here comes Saturn
Mars reached opposition to Earth on January 29th, but another solar system object has been gradually making its way into the evening sky, Saturn. In addition to a beautiful ring system, Saturn holds another distinction, it is the most remote member of the solar system easily visible to the unaided eye. Currently located at a distance of about 830 million miles in the direction of the constellation Virgo, Saturn presents a nearly edge-on view of its ring system to earthbound observers.
Rising above the eastern horizon at 10PM, Saturn reaches it highest spot in the sky at about 4AM. As the weeks go by it will rise earlier each evening. By Valentine’s Day, it will clear the horizon before 9PM and be at its highest elevation by 3AM. During mid to late February, a telescope should offer good views of Saturn before midnight.
In 2004, the Cassini-Huygens probe arrived at the Saturnian system. On Christmas eve, the Huygens lander separated from the orbiter and made its descent to the surface of Saturn’s largest moon, Titan. It touched down in a slush of frozen hydrocarbons on January 14th 2005. The Cassini mission has yielded an abundance of fresh data about Saturn and its moons. Among its many findings, Cassini added nine new members to the already impressive roster of moons bringing the total count up to 61.
Besides Titan, three other moons have shared the spotlight of recent discoveries. In early 2006, NASA released Cassini probe images showing geysers of water vapor jetting into space above the southern hemisphere of Saturn’s moon, Enceladus.
Orbiting within Saturn’s diffuse, outer E ring Enceladus and its water geysers are the leading candidate for the ring’s origin. But, the E ring is dwarfed by another ring found just last year. Because Cassini is too close to Saturn to have made this amazing discovery, credit goes to the Earth trailing infrared-sensing Spitzer Space Telescope.
Shortly before it ran out of helium coolant, Spitzer was able to detect the thermal radiation of the ring’s cool dust and characterize its truly staggering dimensions. Tilted 27 degrees from Saturn’s equatorial plane, the ring’s vertical size equals 20 Saturn diameters. The gigantic ring has a total volume that would take one billion Earths to completely fill. University of Virginia astronomer, Anne Verbiscer, points out that “If you could see the ring, it would span the width of two full moons’ worth of sky, one on either side of Saturn.”
To explain the enormous ring’s origin, scientists have turned to Saturn’s oddball moon, Phoebe. Not only does Phoebe and the new ring travel opposite the direction of most of Saturn’s other moons and ring system, its orbit also matches the tilt of the new ring. This finding may finally explain the strange appearance of Saturn’s two-toned moon, Iapetus.
Iapetus was first observed by Giovanni Cassini in 1671. Several years passed before he understood that Iapetus has one dark side and one light side. But an explanation for how the leading side of Iapetus was dark compared to its brighter, trailing side remained unanswered. It now seems likely that material from the inner part of the newfound ring moves towards Iapetus staining its leading surface just like bugs on the windshield of a moving car.
