astronomy丨the comet neowise, once encountered in 6800, "came you!"-凯发k8娱乐登凯发k8娱乐登录


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astronomy丨the comet neowise, once encountered in 6800, "came you!"
time:  2021-08-18 source: suzhou lanscientific co.,ltd.

comet neowise is known as "the brightest comet in the 21st century in the northern hemisphere". it is a retrograde long-period comet that revolves around the sun and "passes" the earth once every 4,500 to 6,800 years. recently, the comet neowaise crossed the night sky in the northern hemisphere, and people from all over the world have witnessed the comet and its "tail" one after another.


what is a comet

comets are interstellar matter, commonly known as "broom stars".

comets are a type of small celestial bodies in the solar system. composed of frozen material and dust, commonly known as dirty snowballs. a comet is generally composed of a comet head and a comet tail. the comet head includes a comet nucleus and a comet, and the chemical composition of each part is not the same.

the diameter of the comet is generally 50,000 to 250,000 kilometers. according to records, the "champion" of the comet may be regarded as a large comet that appeared in 1811. the diameter of the comet is more than 1.8 million kilometers, which is larger than the sun's diameter of 1.4 million kilometers. big.

the comet nucleus is the core part of a comet, generally 1 to 10 kilometers in diameter, composed of ice and dust particles. the main component of ice is h2o, which contains co2, co and a small amount of nh3, ch4, hcn, ch3cn, cs and so on.

a coma is a star-shaped mist composed of gas and dust around the nucleus of the comet, with a radius of up to hundreds of thousands of kilometers. the main components of the gas are neutral molecules and atoms, including hydrogen, hydroxyl, oxygen, sulfur, carbon, carbon monoxide, amino, cyanide, and sodium. these gases flow out from the center at an average speed of 1-3km/s.

comet tails begin to appear when comets approach the sun, and gradually grow from small to large. when the comet passes the perihelion and is far away from the sun, the comet's tail gradually becomes smaller until it disappears. the direction of the comet tail generally extends behind the sun. when the comet approaches the sun, the comet tail is dragged behind, and when the comet leaves the sun, the comet tail becomes the leader again.

comet tails are very large, and the length and width of comet tails vary greatly. generally, the length of comet tails is between 10 million and 150 million kilometers, and some are amazingly long, which can span half of the sky. generally, the width of the comet tail is between 6000-8000 kilometers, the widest is 24 million kilometers, and the narrowest is only 2000 kilometers.

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classification of comets

comets have three orbits: elliptical, parabolic and hyperbolic. comets with parabolic and hyperbolic orbits can only approach the sun once in their life. once they leave, they will never return and become non-periodic comets; their orbits are elliptical. comets can return to the sun regularly and become periodic comets.

periodic comets are divided into short-period comets (the period of orbiting the sun is shorter than 200 years) and long-period comets (the period of orbiting the sun is more than 200 years). compared with the well-known halley's comet, its average revolution period is 75 or 76 years, and it is the most thoroughly studied short-period comet.


the difference between a comet and a meteor

meteor showers are also called periodic meteors, which are meteor phenomena that occur at the same time every year.

meteors are generally scum from comets, and the orbit of comets is relatively stable. the earth passes through this scum zone every year.

at this time, the slag enters the atmosphere and burns, which is the meteor shower we see.

there are also meteorites that have not been burnt clean and hit the surface of the earth.

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