English: Comet / Deutsch: Komet / Español: Cometa / Português: Cometa / Français: Comète / Italiano: Cometa /
Comet refers to a small, icy, dusty celestial body that orbits the Sun. Comets are typically made up of a mixture of water ice, dust, and other volatile materials, and they are often referred to as "dirty snowballs." When a comet is close to the Sun, the heat of the Sun causes the volatile materials in the comet to vaporize, creating a bright halo of gas and dust around the comet's nucleus, called a coma. The coma is often surrounded by a bright, glowing halo called a coma, which is visible to telescopes and other instruments. The coma and the halo can be several times larger than the nucleus of the comet itself.
Comets are believed to originate in the outer solar system, beyond the orbit of Pluto. They are thought to be remnants of the early solar system, preserved in the cold, dark regions of the outer solar system for billions of years. When a comet is perturbed by the gravitational influence of a planet or other celestial body, it can be pushed into an orbit that brings it closer to the Sun. As the comet gets closer to the Sun, the heat of the Sun causes the volatile materials in the comet to vaporize, creating the coma and halo that are visible from Earth.
There are many different types of comets, ranging from small, short-period comets that take just a few years to orbit the Sun to large, long-period comets that take thousands of years to orbit the Sun. Some comets are highly active and produce large, bright comas and halos, while others are less active and have smaller, fainter comas and halos. Despite their small size and distant origins, comets have played an important role in the history of astronomy and have been the subject of much scientific study.
Here are a few examples of comets that have been studied by astronomers:
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Halley's Comet: Halley's Comet is a short-period comet that orbits the Sun every 76 years. It was named after the English astronomer Edmond Halley, who was the first to predict that the comet was periodic and would return to Earth's vicinity. Halley's Comet is one of the most famous comets in history, and it has been observed by astronomers for hundreds of years. The comet is most famous for its bright, glowing coma and halo, which can be seen from Earth with the naked eye.
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Comet Hyakutake: Comet Hyakutake is a long-period comet that orbits the Sun every 30,000 years. It was discovered in 1996 and was visible from Earth with the naked eye for several weeks. During its close approach to the Sun, Comet Hyakutake produced a bright, glowing coma and halo that was visible from Earth.
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Comet ISON: Comet ISON was a short-period comet that was discovered in 2012. It was expected to be visible from Earth with the naked eye in late 2013 as it made its closest approach to the Sun. However, the comet disintegrated as it passed close to the Sun and was not visible from Earth.
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Comet 67P/Churyumov-Gerasimenko: Comet 67P/Churyumov-Gerasimenko is a small, short-period comet that was visited by the European Space Agency's Rosetta spacecraft in 2014. The spacecraft orbited the comet and even landed a small probe on its surface. The mission provided scientists with a unique opportunity to study the composition and structure of a comet up close.
Overall, comets are fascinating celestial objects that have captivated the imagination of astronomers and the general public for centuries. They continue to be the subject of much scientific study and exploration.