why do some planets have rings around them
Planetary ring systems are complicated, notes
Director, and they are more common than once believed. For ages, Saturn was thought to be the only planet in our solar system with a ring system. But in recent years ring systems have been discovered around Jupiter, Uranus and Neptune as well. There are various theories about planetary rings, like the fantastic rings around Saturn, but we cannot say for sure how they are formed, explains Lattis. One theory is that the rings formed at the same time as the planet and its major moons.
In this case, if material is close to the planet, the planet s gravitational pull is too strong to coalesce into a moon and the particles that would otherwise form a moon spread out in orbit around the planet as a ring. Another idea is that a close call by a moon or comet results in the planet s gravitational tidal force breaking up those bodies, the debris of which then becomes a ring system.
Although astronomers can t say for certain what causes planetary rings, Lattis says that the Cassini spacecraft now in orbit around Saturn is beginning to provide tantalizing new clues to the forces that govern the physics of planetary rings. Why does Saturn have rings? Scientists have ideas about why Saturn has rings, but no one knows for sure. What are Saturn's rings made of? Are they solid like the?
Or are they made of many particles dancing in formation around the planet? Four robotic spacecraft from Earth have visited Saturn Pioneer 11, Voyager 1, Voyager 2, and Cassini. They have revealed many surprising things about Saturn's rings. The small color differences in Saturn's rings have been enhanced in this picture from Voyager 2 data. Over 60 bright and dark ringlets show up in this color enhanced image from Voyager 2 data. The rings are about 400,000 kilometers (240,000 miles) wide.
That's the distance from the Earth to the Moon! But the rings are as little as 100 meters (330 feet) thick. They range from particles too tiny to see to "particles" the size of a bus. Scientists think they are icy snowballs or ice covered rocks. There are actually many rings maybe 500 to 1000. There are also gaps in the rings. (That's why we put some black rings on our model Saturns. ) The Cassini spacecraft arrived at Saturn in July 2004 and is still there.
It is studying Saturn, its rings, and its moons much more thoroughly than the earlier spacecraft could. Cassini also carried a probe, called Huygens (HOY-guns), that parachuted into the atmosphere of Saturn's giant moon Titan. Huygens sent back amazing information and images from this strange world whose surface we have never seen. Cassini and Huygens have made exciting new discoveries.
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