Kepler’s Law：开普勒定律.ppt

Solar System Objects -Meteoroid: A small rock or boulder classified as debris from the solar system. Any debris that enters the atmosphere is known as a meteor and any debris surviving an impact on the ground is known as a meteorite. What is the difference between a Meteoroid, Meteor and a Meteorite? -Comets: A chunk of dust and ice left over from the formations of the solar system. Usually consist of the nucleus of dust and ice with a tail. -Asteroid: Rocky and metallic bodies within the solar system that orbit the sun. Kuiper Belt -Kuiper Belt: A region of space outside the orbit of Neptune that contains dwarf planets and other small objects. This region extends from around 40 AU to 80 AU and is shaped in orbit around the sun as a donut ring. The sun’s outmost reach is said to be within the Kuiper Belt, from where the solar system ends and begins interstellar space, known as the heliopause. What sort of objects are contained in the Kuiper Belt? Oort Cloud -The Oort Cloud: A huge spherical region of small, deep frozen objects that form the nuclei of comets. This region begins at about a half a light year radius from earth to 1.5 light years (or 50,000 AUs). It was proposed by Dutch Astronomer Jan Oort when studying comets. Noticing that they all had their aphelia, or farthest distance from the sun, in this region, possibly indicating that this is where comets are coming from and returning to. The Oort Cloud is estimated to contain a trillion dormant comets. What sort of objects originate in the Oort Cloud? What is the radius of the Oort Cloud from the sun? Star Formation -Star Formation: Stars form from dense regions of great gas and dust clouds within a galaxy, usually nebulas. By gaining enough mass and gravity, the star begins to emit radiation and ultimately create enough heat within the core to cause nuclear fusion. Finally when the star gets hot enough, the true hydrogen fusion within the star begins, giving birth to a very hot star emitting