Saturn
Saturn is the sixthed planet in order from the sun and the second largest in our solar system. It's distinctive features are its rings system, first seen in 1610 by Galileo. He described the rings as ansae (hands) due to the point the he did not quite understand that the rings where seperate from the planets body. Huygen's, a Dutch astronomer, in 1655 was the first to correctly describe Saturns rings. The rings are named in order of their discovery, from the planet outward they are knnown as the D, C, B, A, F, E,and Grings. These rings comprise more than 100,000 individual ringlets, all of which circle the planet. Saturn is also known for its many moons.
Saturn appears as a yellowish object from earth, one of the brightest in the night sky. Through a telescope the A and B rings are easily seen, whereas only under optimal conditions can the D and E rings be seen. Sensitive earth-based telescopes have deteceted nine satellites, and in the haze of Saturn's gaseous envelope, pale belts and zonees parallel to the equator can be distinguished. Three U.S. spacecrafts have enormously increased knowledge of the Saturnian System. These spacecrafts carried cameras and instruments for analyzing the intensities and polarizations of radiation in the visible, ultraviolet, infrared, and radio portions of the electromagnetic fields and for detecting charged particles and interplanetary grains.
The density of Satun is eight times less than that of Earth because the planet consists mainly of hydrogen. The enomous weight of Saturn's atmosphere causes the atmospheric pressure to increase rapidly toward the interior, the hydrogen gas condenses into a liquid. Closer to the center of the planet, the liquid hydrogen is compressed into metallic hydrogen, which is an electrical conductor. Electrical currents in the metallie hydrogen are responsible for Saturn, heavy elements have probably settled into a small rocky core with a temperature close to 15,000 degrees Celsius.
Saturn is still settling gravitationally, following its original accretion from gas and dust nebula from which the solar system was formed more than 4 billion years ago. This contraction generates heat,
Saturn's atmosphere constituents are, in order by mass, 88 percent hydrogen, 11 percent helium, and the remainer comprises traces of methane, ammonia, ammonic crystals, and other gases such as ethane, acetylene and phosphine. Images taken by Voyageer showed whirls and eddies of clouds occurring deep in a haze that was very thick, due to Saturn's low temperatures.
The temperature of Saturn's clouds tops are close to 176 degrees Celsius. Based on the movement of Saturnian storm clouds, the period of rotation of the atmosphere near the equator is about 10 hr. 11 min. Radiio emission that have been detected comming from the body of the planet indicates that the body of Saturn and its magnetosphere rotata with a period of 10 hr. 39 min. 25 sec. The approximate 28.5 min difference betwwen these two times indicates that Saturnian equatorial winds have velocities close to 1700 km/hr.
Saturn's magnetosphere consists of a set of doughnut shaped radiation belts in which elcetrons and atomic nuclei are trapped. The belt extends to more than 2 million km from the center of Saturn and even farther in direction away from the sun, although the size of magnetosphere fluctuates, depending on the intensity of the solar wind. The solar wind and Saturn's rings and satellites supply the particles that are trapped in the radiation belts. The magnetosphere interacts with the ionsphere, the topmost layer of Saturn's atmosphere, causing auroral emissions of ultraviolet radiation.
The visible rings stretch out to a distance of 136,200 km and in many regions may be only 5 km thick. They are though to consist of aggregrates of rock, frozen gases, and water ice ranging in size from less than .0005 cm. in diameter to about 10 m in diameter.
There is an apperant seperation between the A and B rings called Cassini's division. Voyager's television imaged five new faint rings within Cassini's division. The wide B and C rings appear to consist of hundreds of ringlets, some slightly elliptical, that exhibit rippling density variations. The gravitational interaction between rings and satellites, which causes these density waves, is still not understood. The B ring appears bright when viewed from the side illuminated by the Sun, but dark on the other side because it is dense enough to block the sunlight. Images have also revealed in the B ring radial, rotating spokelike pattern
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This page was written by Khadeisha Samuels in the Astronomy class of BCC/ Broward County, July 1998. |