What is a comet?

A comet is a small celestial body that orbits the Sun, usually in a highly elliptical orbit. It is composed of dust, ice, and other frozen gases. As a comet gets closer to the Sun, it begins to heat up and release gas and dust in the form of a glowing coma and a long, trailing tail.

Comets are believed to be remnants from the early solar system and can provide valuable information about its formation. They are also of interest to scientists because they contain organic molecules, which are the building blocks of life. Comets are named after their discoverers or for the observatory or satellite that first detected them.

Comets are visible from Earth with the naked eye, and their appearances have been recorded throughout history. Some famous comets include Halley's Comet, which appears every 76 years, and Comet Hale-Bopp, which was visible to the naked eye for a record 18 months in 1996 and 1997.

A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or coma surrounding the nucleus, and sometimes a tail of gas and dust gas blown out from the coma. These phenomena are due to the effects of solar radiation and the outstreaming solar wind plasma acting upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles.

Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, which lie beyond the orbit of Neptune. Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun by gravitational perturbations from passing stars and the galactic tide.

Comets are thought to be among the most primitive objects in the Solar System, dating back to its formation. They are therefore a valuable source of information about the early Solar System. Comets have been observed for centuries, and they have been the subject of much speculation and superstition. In the Middle Ages, comets were often seen as omens of disaster, and they were sometimes blamed for plagues and other calamities. Today, we know that comets are relatively harmless, but they are still fascinating objects that continue to intrigue us.

Some of the most famous comets include Halley's Comet, which returns to the inner Solar System every 76 years, and Comet McNaught, which was the brightest comet seen in the Northern Hemisphere in over 40 years in 2007. Comets are a beautiful and awe-inspiring sight, and they are a reminder of the vastness of space and the mysteries that still await us.