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Comets

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by

Alicia Watson

on 16 December 2013

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Transcript of Comets

Comets !!!


Who discovered the first comet ?
Gottfried Kirch first discovered a comet in November 1680 with a telescope. In 1770 a man named Charles Messier located more comets than anyone had found before. The Chinese seen and drew comets all the way back to 1059 BC.
Comet Life Cycle
• Departure
Some comets are not bound to the sun, on orbits that take them out of the solar system.

Extinction
Comets lose ice and dust each time they come near the sun, leaving behind trails of debris. Eventually, they can lose all their ice, with some turning into fragile, objects similar to asteroids.

• Breakup
Other comets, upon losing all their ice, break up into clouds of dust.

• Collisions
The orbits comets take sometimes end with them colliding with planets and their moons. Many impact craters seen in the solar system were caused by such collisions.

http://science.discovery.com/video-topics/space-videos/comets.htm
top 5 famous comets
By Jessika ,Alicia, Joella

Comets
They are the most brilliant and most rare objects in the whole universe. These soaring ice balls made out of dust with their beautiful tails come from the outer realms of the Solar System.

What are planetesimals?

Any of innumerable small bodies thought to have orbited the sun during the formation of the planets. ( Definition)




Where do comets come from?
Comets come from two places: The Kuiper Belt and the Oort Cloud
What is an Oort Cloud?
A swarm of comets orbiting the sun at a distance of one to two light-years, proposed as a source of comets that pass near the sun. ( Definition ) Long-period comets (those which take more than 200 years to complete an orbit around the Sun) originate from the Oort Cloud
What is a Kuiper Belt ?
A disk-shaped region in the outer solar system lying beyond the orbit of Neptune and extending to a distance of about 50 astronomical units, containing thousands of small icy bodies, some of which are on highly elliptical orbits, periodically visiting the inner solar system as comets. ( Definition ) Short-period comets (those which take less than 200 years to complete an orbit around the Sun) originate from the Kuiper Belt.

Why do comets exist ?

Comets are believed to be the "left-over" matter from the formation of the Solar system. All of the material near the center of the system collapsed to form the Sun, while heavier elements farther out came together to form the planets. Far out from the sun, much of the remnants clumped together in a region called the Oort Cloud. A chunk of frozen matter is disturbed from the Oort Cloud and falls toward the Sun. As the Sun heats it, the material of the comet, which is similar to a snowball with a few rocks, begins to melt and vaporize, and the sunlight causes the vapor to glow. The tail of the comet will sometimes hit a planet, such as the Shoemaker-Levy comet that smashed into Jupiter. Some scientists, notably Luis Alvarez, theorize that a comet striking the Earth 65 million years ago may have killed off the dinosaurs.
How did comets form?
Comets are some of the material left over from the formation of the planets. Our entire solar system, including comets, was created by the collapse of a giant, diffuse cloud of gas and dust about 4.6 billion years ago. Much of the matter formed into planets, but some remained to form small lumps of frozen gas and dust in the outer region of the solar system, where temperatures were cold enough to produce ice





How do comets effect us ?
http://science.discovery.com/video-topics/space-videos/comets.htm
Comet Facts

A comet is a relatively small solar system body that orbits the Sun. When close enough to the Sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail.


The coma is created as the comet gets closer to the Sun, causing water, carbon dioxide and other compounds to sublime (quickly changing from solid to gas) from its surface.


Comets are made of ice, dust and small rocky particles.


The name comet comes from the Greek word meaning ‘hair of the head’, it came from the Greek philosopher Aristotle who observed comets as ‘stars with hair’.


Short term comets (also known as periodic comets) have orbital periods of less than 200 years while long term comets have orbital periods of over 200 years.


Why do comets have tails?


A comet's tail is its most interesting feature. As a comet approaches the Sun it develops an enormous tail of material that extends for millions of kilometers away from the Sun. A comet's nucleus is very cold and its material is frozen when its far away from the sun. Water ice, as well as other compounds such as carbon dioxide and carbon monoxide ice, may be found in the nucleus. This icy nucleus changes faster when a comet approaches the Sun. The intense solar wind from the Sun transforms the solid nucleus directly into a vapor, skipping the whole the liquid process this is called sublimation. The vapor helps stir things up in the nucleus, forcing the core to form a cloud-like mixture of gas and dust around it, called the coma. There, sunlight and the solar wind interact with the ingredients, creating the tails. The ingredients in the coma determine the types and number of tails. Some comets may appear to have no tails, but they really do. They are simply very faint. Scientists can identify these tails by using special filters that are sensitive to dust or gas emissions. Other comets, like Hale-Bopp, which could be seen from Earth in 1997, have very prominent tails. Although Hale-Bopp's tails could be seen visibly from Earth, scientists using sensitive cameras identified a much more complicated tail structure. One of these images revealed a long, curving dust tail. Other pictures showed dust and gas ion tails. There was even an image of a dust tail and two gas ion tails. The different tails provide scientists with important information about the internal chemistry and structure of a comet's nucleus
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What path do comets follow through the solar system?


Planets have nearly circular orbits, while comets have elongated paths around the Sun. A comet is at aphelion when its orbit is farthest from the Sun. It is at perihelion when it is closest to the Sun. Due to gravitational effects, a comet will travel fastest at perihelion and will slow down as it approaches aphelion. Comets can be classified by their orbital period: that is, the time it takes them to make one complete trip around the Sun. Comets with short and intermediate orbital periods — like Comet Halley, whose orbital period is 76 years — spend most of their time between Pluto and the Sun. These comets began as asteroids in the Kuiper belt, but a gravitational "push" from the planets, especially Jupiter, swung them closer to the Sun. Some of their orbital periods are shorter than 200 years. Comet Shoemaker-Levy 9 is an example of a comet that has been radically perturbed by Jupiter's gravitational effects. A long-period comet will have an orbital period of more than 200 years. Hale-Bopp, for example, completes an orbit every 2,400 years. Hale-Bopp once completed an orbit every 4,000 years, but during its last visit to the inner solar system, the comet passed so close to Jupiter that the planet's gravitational force altered its orbit. Scientists think that this type of comet spends most of its time way out in the Oort Cloud at the farthest edge of our solar system.

1. Halley’s Comet
2. The Eclipse Comet of 1948
3. Comet Lovejoy
4. Comet McNaught
5. The Great Comet of 1680

What are comets?
A comet is a small object which scientists sometimes call a planetesimal. They are made out of dust and ice, kind of like a dirty snow ball. When passing close to the sun, heats up and begins to outgas displaying a visible tail.
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