What's Comet: His Name Usually The SAME As The Meeter

Illustration of Comet passing through space. (photo: Justin W - Unsplash)

YOGYAKARTA - If you ask what comet is? Of course, this comet is one of the most spectacular objects in the sky, with a luminous coma as well as a long tail of dust and ion tail. Comets can appear randomly from all directions and provide a remarkable appearance and always change for months as they move in very eccentric orbits around the Sun.

Comets are important to scientists because they are the primitive objects left over from the formation of the solar system. They include the first solid objects to form in the solar nebula, clouds of dust and interstellar gas to collapse where the Sun and planets form.

Comets form in areas outside the solar nebula that are cold enough to condense volatile ice. This is generally thought to exceed 5 astronomical units (AU; 748 million km, or 465 million miles), or beyond Jupiter's orbit.

Since comets have been stored in orbits far beyond the planet, they have undergone several modification processes that have melted or altered larger bodies in the solar system. Thus, they store physical and chemical records of ancient solar nebulae and processes involved in planetary system formation.

Constructure in Comets

Comets consist of four visible parts: nuclei, coma, ion tails, and dust tails. Nucleus is a solid object that is usually about a few kilometers in diameter and consists of a mixture of volatile ice (mainly water ice) and silicate and organic dust particles. Coma is a freely outgoing atmosphere around the nucleus that forms when comets approach the Sun and volatile ice, carrying with dust particles that mix tightly with frozen ice in the nucleus.

The dust tail forms from such dust particles and is exhaled by the pressure of solar radiation to form a long curved tail that is usually white or yellow. The ion tail forms from an volatile gas in a coma when they are ionized by ultraviolet photons from the Sun and blown by the solar wind. The ion tail points almost exactly away from the Sun and is blue in color due to the presence of CO+ ions.

Comets differ from other bodies in the solar system because they are generally in orbits that are much more eccentric than planets and most asteroids and are much more inclined towards ecliptics (Earth orbital fields). Some comets appear to come from a distance of more than 50,000 AU, a fraction of the distance to nearby stars.

Its orbital period can reach millions of years. Other comets have shorter periods and smaller orbits that carry them from orbits of Jupiter and Saturn into orbits of terrestrial planets. Some comets even appear to originate from interstellar space, pass through the Sun on an open hyperbolic orbit, but are actually members of the solar system.

Comets are usually named after their inventors, although some comets (mis., Halley and Encke) are named after scientists who first learned that their orbits are periodic. The International Astronomical Union (IAU) prefers a maximum of two inventors in the comet name.

In some cases where a comet has disappeared (its orbit is not determined well enough to predict its return), the comet is named according to its original inventor and also the observer who found it again.

The designation "C/" before the comet's name showed that it was a long-period comet (a period of more than 200 years), while "P/" showed that comet is periodic; that is, it returns regularly, an interval that can be predicted to be less than 200 years. The "D/" show that the comet is dead or destroyed, such as D/Shoemaker-Levy 9, comet whose component hit Jupiter in July 1994. The figure that appeared before the comet's name showed that the comet was periodic; the comet was given a number according to the periodic definite sequence. The comet 1P/Halley was the first comet known as periodic comet and was named according to British astronomer Edmond Halley, who determined that comets were periodic.

Comet Identification Process

In 1995 IAU implemented a new identification system for every comet, both periodic and long periodic. The system uses the discovery year of comet, half month in the year denoted by the letters A to Y (with I eliminated to avoid confusion), and the numbers signaling the comet sequence were found in that half month..

So, Halley's Comet was designated as 1P/1682 Q1 when Halley saw it in August 1682, but 1P/1882 U1 was first spotted by astronomers before the perihelion (closest point to the Sun) which was predicted in 1986.

This identification system is similar to the one now used for the discovery of asteroids, although asteroids were only established when they were first discovered. (Asteroids were then given an official number and catalog name.) Previously, numbers after the name of the periodic comet showed its order among comets found by such individuals or groups, but for new comets there would not be such a differentiator number.

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