Comets

Comets

Comets are very beautiful when they pass close to the sun but they are merely giant balls of frozen water mixed with cosmic dust. There is also a small percentage of ammonia, methane, and CO₂. These chunks are theorised to have originated from the forming of giant planets like Saturn, Jupiter, Neptune, and Uranus, and each comet is usually the size of one of the Rocky Mountains. There are four parts to a comet: nucleus, coma, plasma tail, and dust tail. The nucleus is the only permanent part of the comet. Although it has never been seen, there is no doubt of its existence. The brightness of the comet can depend on how large the nucleus' diameter is since these spherical forms can scatter sunlight like a mirror.

Comets have a wide range of orbital periods, ranging from a few years to hundreds of thousands of years. Short-period comets originate in the Kuiper Belt, or its associated scattered disc,[1] which lie beyond the orbit of Neptune. Longer-period comets are thought to originate in the Oort cloud, a cloud of icy bodies in the outer Solar System that were left behind during the condensation of the solar nebula. Long-period comets plunge towards the Sun from the Oort Cloud because of gravitational perturbations caused by either the massive outer planets of the Solar System (Jupiter, Saturn, Uranus, and Neptune), or passing stars. Rare hyperbolic comets pass once through the inner Solar System before being thrown out into interstellar space along hyperbolic trajectories.

Comets come from the outermost regions of the solar system called the Oort cloud, some 50,000 AU from the Sun.

The Sun's gravitational field is the dominant force out to around 2 light-years although beyond the Oort cloud there is still much that is not known beyond.

The structure of a comet