User talk:Gwen ryan third

Comet Questions

Question: Some questions about comets... any help would be appreciated. What are comets composed of? How fast do they move? How many are known? How many can be seen? Where are they located? What happens to them? Do they ever die out? What would happen if a comet hit the earth? How big does a comet have to be to make it through the atmosphere? How do people calculate their speed and mass? anthony w thompson

Answer: Comets are thought to be "dirty snowballs" composed mostly of water ice and methane ice. They travel at speeds around 20,000 MPH. Some appear only once, then leave the solar system or break up. Some return periodically to the inner solar system (like Halley's). Most are thought to spend most of their time in th e Oort Cloud (check a good encyclopedia or an astronomy text). They can only been seen when they enter the inner solar system and reflect the light of the sun. Their tails are produced by material evaporating off the surface. Comets do not travel throu gh the atmosphere unless they're on a trajectory to hit the earth. If a comet hit the earth, the results would be catastrophic: scientists think that might have been responsible for the extinction of the dinosaurs. Their speed and mass are calculated from th eir different positions in the sky over time. hawley