The Oort Cloud (What/Where is the Oort Cloud and What is in it?) The Oort Cloud is a huge cloud of comets lying far beyond the orbit of Pluto. Trojan AsteroidsThey share Jupiter’s orbit remaining 60 degrees ahead or behind the planet as it moves around the Sun. They are held by a delicately but stable balance between the gravitational fields of Jupiter and the Sun.Shield VolcanoesThe most common type of volcanoes on the planet are known as shield volcanoes. They are built up over long periods of time by successive eruptions and lava flows. A characteristic of shield volcanoes is the formation of a caldera, or crater, at the summit when the underlying lava withdraws and the surface collapses.They are very common on Venus.Discovery of Extrasolar planetsThere are currently more than 350 extrasolar planets, which are planets that orbit stars other than the Sun. Most of them are large.Jupiter’s Magnetic Field (How did it form)The combination of rapid overall rotation and an extensive region of highly conductive fluid in its interior gives Jupiter by far the strongest planetary magnetic field in the solar system. The field at the cloud tops is some 14 times that of Earth, but taking the planet’s radius into account implies an intrinsic field strength some 20,000 times Earth’s. Jupiter is surrounded by a vast sea of energetic charged particles (electrons and protons), somewhat similar to Earth’s Van Allen belts but much larger. Why does one side of the Moon Face the Earth?The same side of the moon always faces the Earth. The "dark side" of the moon is not actually dark -- it gets cycles of day and night just like most places on Earth -- it is just so named because we never see it. The "far side of the moon" is a more correct term.The reason that one side of the moon is never visible from the Earth is because the moon spins once on its axis in precisely the same amount of time it takes to revolve around the Earth. If its rate of rotation were slightly different than its rate of revolution, we would eventually be exposed to the entire surface of the moon. However, these two intervals have been equal for all of recorded history, and probably for millions of years longer.This otherwise bizarre phenomenon can be explained in terms of a subtle effect generated by gravitation and friction. Through their mutual gravitational attraction, the Earth and the moon create tidal bulges on each other. One bulge faces in the direction ofthe other body, and one faces away. These bulges generate heat through the friction of rock rubbing against itself. Because the gravitational force of the Earth on the moon is greater than vice versa, the
moon experiences the greater braking effect. Over time, the moon's rotation has progressively slowed until the rate of rotation matches the rate at which the tidal bulge moves around the body. The Earth's rate of rotation slows over time due to moon-created tidal forces, but the
You've reached the end of your free preview.
Want to read all 10 pages?
- Spring '13
- Solar System, Planet, Pluto