Comet

Comet Hale-Bopp 1995O1

Anglo-Saxon Chronicle - cometa (British Library Cotton MS Tiberius A VI, folio 10v)

Structure of a comet

Comet Hartley 2

Comet wild 2

Comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind 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.

Origins and Discovery

Comets are believed to originate in the Oort Cloud and the Kuiper Belt, two distant regions of the Solar System filled with icy bodies. The gravitational perturbations of the outer planets (like Jupiter and Saturn) or nearby stars can send these icy bodies into the inner Solar System, where they become visible as comets. Historically, comets have been recorded and observed by many cultures and are often featured in ancient mythology and religions.

Composition and Structure

The nucleus of a comet is made up of ice (water, carbon dioxide, ammonia, and methane) and dust. This nucleus is often described as a "dirty snowball." As a comet approaches the Sun, the ice starts to sublimate, or turn directly from a solid to a gas, creating the coma and tail. The coma is a temporary atmosphere that surrounds the nucleus, while the tail is made up of gas and dust particles pushed away from the Sun by solar wind and radiation pressure.

Types of Comets

Comets are categorized into two main types based on their orbital periods: short-period comets and long-period comets. Short-period comets, also known as Jupiter-family comets, have orbits that last up to 200 years and are believed to originate from the Kuiper Belt. Long-period comets have orbits that can last thousands of years and are thought to come from the Oort Cloud.

Famous Comets

Some of the most famous comets include Halley's Comet, which appears every 76 years, Comet Hale-Bopp, which was visible to the naked eye for a record 18 months in 1996-1997, and Comet Hyakutake, known for its long and bright tail during its 1996 appearance.

Observation and Study

Comets have been observed and studied for centuries, both with the naked eye and with telescopes. Modern observations are conducted using ground-based telescopes and space missions, such as the Rosetta mission, which landed a probe on the nucleus of comet 67P/Churyumov–Gerasimenko in 2014. These studies help scientists understand the composition and behavior of comets, as well as the conditions of the early Solar System.

Cultural Impact

Throughout history, comets have inspired awe, fear, and wonder. They have been seen as omens of significant events, from victories in battle to the births and deaths of notable figures. Today, comets continue to fascinate both scientists and the public, offering spectacular celestial shows and insights into our cosmic origins.