Molecules released by the evaporation stream away from the comet and generate a jet-type reaction that pushes the comet away from the Sun and slows it down. If the nucleus is rotating, the force may be in another direction and cause it to speed up. Where Do Comets Come From? The Oort Cloud It is thought that most comets originate in a vast cloud of ice and dust that surrounds the solar system.
They are thought to originate in the Oort cloud. The Oort cloud has never been observed, but is believed to have at least 10 12 icy objects located between AU and , AU in a spherical distribution around the Sun.
As comets travel close to the Sun, the Sun's heat begins to vaporize the ices and causes them to form a fuzzy, luminous area of vaporized gas around the nucleus of the comet known as a coma. Outside the coma is a layer of hydrogen gas called a hydrogen halo which extends up to 10 10 meters in diameter.
The solar wind then blows these gases and dust particles away from the direction of the Sun causing two tails to form. These tails always point away from the Sun as the comet travels around it. One tail is called the ion tail and is made up of gases which have been broken apart into charged molecules and ions by the radiation from the Sun. The other tail is called a dust tail and normally appears white.
The dust in this tail is less strongly affected by the solar wind since the particles of dust are much larger than the ions in the ion tail. That is why the dust tail is usually curved rather than straight, and does not point directly away from the Sun, because it is also influenced by the motion of the comet.
The tails of the comet can be extremely large and my extend a distance of up to 1 AU the distance between the Earth and the Sun! The Kuiper belt is a region between about 30 and 50 AU from the Sun in the plane of the ecliptic. Comets orbit the Sun just like planets and asteroids do, except a comet usually has a very elongated orbit. As the comet gets closer to the Sun, some of the ice starts to melt and boil off, along with particles of dust.
These particles and gases make a cloud around the nucleus, called a coma. The coma is lit by the Sun. The sunlight also pushes this material into the beautiful brightly lit tail of the comet. Key Facts Comets Comets are frozen leftovers from the formation of the solar system composed of dust, rock, and ices.
Kid-Friendly Comets Comets orbit the Sun just like planets and asteroids do, except a comet usually has a very elongated orbit. JPL's lucky peanuts are an unofficial tradition at big mission events. It's suspected that about 5, years ago a comet swept within 23 million miles of the Sun, closer than the innermost planet Mercury. Models and lab tests suggest the asteroid could be venting sodium vapor as it orbits close to the Sun, explaining its increase in brightness.
A one-time visitor to our inner solar system is helping explain more about our own origins.
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