All about Comets

Not too long ago, many people thought that comets were a sign that something terrible was about to happen. People didn't understand about how objects in the sky moved, so the sight of a comet must have been very scary. Now we know that comets are lumps of ice that come flying into the solar

Comets are believed to originate from a dense shell of material surrounding the outer regions of the solar system known as the Oort cloud. It is thought that the gravity from a passing star or other object may force some of these comets to begin moving in towards the Sun.

As the comet comes closer to the sun, near the region of space occupied by Mars it becomes warm enough for the comet to begin to evaporate. When evaporation begins, the coma and tail form.  

Some have even suggested that our Sun may have an unseen companion that passes close in a highly eccentric every few hundred million years. This companion star may cause swarms of comets to head toward the inner solar system, increasing the chances of collisions. This would help to explain why our planet has experienced a cycle of mass extinctions every few hundred million years.

Scientists are going to use the Rosetta mission to land a probe onto the surface of comet Wirtanen. This and other comet missions (see link below) will certainly help scientists understand the very center of comets! As the comet comes closer to the sun, near the region of space occupied by Mars it becomes warm enough for the comet to begin to evaporate. When evaporation begins, the coma and tail form. Some comets make repeated trips Jets of gas and dust form long tails that we can see from Earth. These tails can sometimes be millions of miles long.

Unfortunately, we don't get to see comets very frequently. In 1985-1986, a spacecraft called Giotto visited the most famous comet of all, Halley's comet. In 1994, a comet named Shoemaker-Levy, ran into Jupiter!

In 1996 and 1997, we could see comet Hyakutake, and comet Hale-Bopp from Earth. Hale-Bopp was one of the brightest comets ever seen from Earth. Comet Linear was discovered in 1999 and came closest to the Sun in July 2000.

Now scientists have identified a class of comets known as small comets. Originally  people  believed these were snowballs from outer space.

Cosmos...