Dec 25, 2012

Comet's naming method


1995 years ago, the comet is in accordance with the annual found that the order of arrangement of the English lower case. 1994, discovered a comet 1994a, infer that, after a period of observation to determine the comet's orbit and fix it over the priorities of the perihelion of the comet, came in the years after the Roman numerals Ⅰ, Ⅱ (This number is usually two years after the end of the year to compile). Shoemaker? Levy 9 comet number for 1993e and 1994 Ⅹ.
In addition to the number, some comets are usually discoverer surname named. Comet can labeled three discoverer's name, the English name of the Shoemaker Levy 9 comet Shoemaker-Levy 9.
From 1995, the nomenclature of the International Astronomical Union Reference asteroid, comet ID law in two weeks for the unit, in alphabetical order. I and Z do not have removed all of the letters of the English alphabetical order of the remaining 24, such as the first half of January as A, January second half for B thus infer to December second half for Y.
And then
  Comet
The comet discovered 1,2,3 .. digital serial arrangement of the same month and a half. Furthermore, in order to facilitate the identification comet status of the serial numbers marked:
A / might as asteroids
P / confirm return of a more short-period comet P in front of the table number on a periodic comet (as Halley's Comet 1P/1982 U1 or referred 1P also)
C / long-period comets (more than 200-year cycle, such as Haile Bopp Comet C/1995 O1)
X / not yet calculated the orbital elements of the comet
D / the longer regression or comet may have disappeared (such as Shoemaker? Levy 9 comet D / 1993 F2)
Attached S / satellite of the newly discovered planet
If the comet is broken, split into more than the nucleus, together with the number and then-A,-B .. to distinguish each nucleus. Return of the comet aspects, such as the comet again observed regression in P / (or may be the D /) mark again before plus a serial number given by the IAU Minor Planet Center, in order to avoid the return of the comet. For example, the following tag: 1P/1682 Q1 = 1P/1910 A2 = 1P/1982 U1 = 1P/Halley = Halley's Comet in Halley's Comet.

Comet's Structure

The comet does not have a fixed volume, it is away from the sun, a small volume; close to the sun, coma becomes larger and larger, the tail becomes longer, the volume becomes enormous. Tail longest actually up to more than 200 million kilometers. The comet quality is very small, The average density of the nucleus of one gram per cubic centimeter. Coma and tail of the material is extremely thin, its quality accounted for only 1% to 5% of the quality, or even smaller. The comet substance is mainly composed of water, ammonia, methane, cyanide, nitrogen, carbon dioxide, etc., the nucleus by condensing into ice water, and carbon dioxide (dry ice), ammonia and dust particles mixed composition "dirty snowball"! General comet is composed by two parts of the comet head and tail. The comet head including the two parts of the comet nucleus and coma. From 1920 sounding rockets, satellites and spacecraft after detection of the comet at close range, and surrounded by a giant cloud of some comets out of coma by a layer of hydrogen atoms, known as the "coma cloud" or "hydrogen cloud". So we can say that the comet head to the actual composition of the nucleus, coma and coma cloud. The comet nucleus is the the comet most central, most essential, the most important part. Generally considered to be solid, and is composed of stones, iron, dust and ammonia, methane, and ice. The small diameter of the comet nucleus, a few kilometers to a dozen kilometers, only a few hundred meters. Coma: the nucleus of gas and dust around the planet like mist. Radius of up to hundreds of thousands of kilometers, the average density of less than a billionth of a billionth of one of the Earth's atmospheric density (about 1 g / cc). Through spectral and radio observations, the coma gas main ingredient is neutral molecules and atoms, including hydrogen, hydroxy, oxygen, sulfur, carbon, carbon monoxide, an amino, cyano, is satisfied, etc., and also found that a relatively complex cyanide hydrogen (HCN) and methyl cyanide (CH3CN) compound. These gases flowing outward from the center to an average of 1-3 km / sec velocity. Coma cloud: cloud by hydrogen atoms in the coma, it is also known as the hydrogen cloud. Up to 100 million to 10 million kilometers in diameter, but some comet coma cloud. According to the characteristics of the shape and composition of the comet head, can be divided into the "no-fat comet head, bulbs shaped comet head, anchor-shaped coma head and so on. The tail of the comet close to the sun about 300 million kilometers (2 astronomical units) began to appear, gradually from small to great changes long. When the comet perihelion (comets come from the sun that) away from the sun, the tail gradually smaller until no. The general direction of the tail always carrying the extension of the sun, when the comet close to the sun, the comet tail trailing behind, when the comet from the sun to flee, the tail has become a leading. Tail of the large volume, but the material is very thin.Tail length, width, the general tail length of between 10 million to 150 million one thousand meters, and some much longer surprising, across half the sky, such as the 1842 Ⅰ comet's tail as long as 320 million kilometers, extending from the sun to the orbit of Mars. General tail width between 6000-8000 km, most of the 24 million meters wide, the narrowest of only 2,000 kilometers. The size of the repulsion according to the shape of the tail of the sun, the tail is divided into two major categories. A class for "ion tail" by the plasma gas composition, such as carbon monoxide, hydrogen, carbon dioxide, carbon, hydrogen group, and other ionizable molecule. Such relatively straight, thin and long tail, so-called "gas tail or tail type I Other for the dust tail is composed of dust, yellow dust repulsion the sun photon radiation pressure to form. The tail is bent, bending larger, wide, referred to as II-type impeller; maximum bending process, and the short, wide, referred to as III-type impeller.In addition, there is something called the "abnormal tail, the tail extends toward the solar system, the direction of the fan-or spike-like. Usually a comet tail of the two or more different types.

The comet's orbit


The comet's orbit is an ellipse, parabola, hyperbola three.

Elliptical orbit of the comet also known periodic comet, the other two tracks is also called non-period comets. Periodic comet is divided into short-period comets, and the long-period comets. The general comet by the comet head and tail. The comet head containing the nucleus and coma two parts, and some even coma cloud. Not all comet has a nucleus, coma, tail structure. Ancient China to the morphology of the comet has a great deal of research in the Western Han tombs unearthed in Mawangdui silk manuscripts on painting 29 comets plans. Jin astronomical annals clearly shows that the comet will not shine due to reflected sunlight, as we have seen, and the tail of a comet in the direction away from the sun. Of a large body of the comet, but its quality is pitifully small, and even the the large comet quality is not the ten-thousandth of the Earth. Since comets are frozen with various impurities, dust, away from the sun, it's just a small cloudy spots; close to the sun, due to the evaporation of the solidified body, gasification, swelling, eruption, it on the tail of a comet. Tail volume dramatically, up to hundreds of millions of kilometers. It shapes, some of the more than one's general extends to deviate from the direction of the sun, and closer to the sun tail longer. The great number of comets in the universe, but observed only about 1600. Very different from the comet's orbit, the orbit of the planet, it is very flat oval, some even parabolic or hyperbolic orbits. Comet of the orbit is elliptical regularly return to the sun around, called a periodic comet; comet orbit is parabolic or hyperbolic, life can only close to the sun once Once departed, never to return, referred to as non-periodic comet type of comet perhaps originally not a solar system members, they are just from outside our solar system passing accidentally broke into the solar system, and later hesitate to return to the vast depths of the universe. The cycle is divided into short-period comets (orbital period shorter than 200 years around the sun) and long-period (orbital period of over 200 years around the sun) comet.
Has calculated more than 600 comets orbit. Comet's orbit may be affected by the influence of the planets, produce changes. When the comet by planetary impact of accelerated, its orbit will become flat, and even become parabolic or hyperbolic, so that the comet from the solar system;, the eccentricity of the orbit will be smaller when the deceleration of the comet, so that the long-period comets change for short-period comets, even from non-periodic comet becomes periodic comet so capture.

Observation of Comet


In the past, except very far away from the sun, the comet's long, bright sparse tail, this gives people the impression that the comet is very close to the earth, even in our atmosphere. 1577 Tycho pointed to different locations when viewed from the Earth, the comet does not show the orientation is different: his right to come they must be very far from the conclusion. Comet belongs to the small bodies of the solar system. Whenever comet close to the sun, its brightness rapidly enhanced. The observations of the comet far from the sun along highly elongated elliptical motion, and the sun is a focus of the ellipse, Kepler's first law. The comet most of the time running in a place far from the sun, where they are invisible. Only when they are close to the sun to see. About of 40 comet orbital period is relatively short (less than 100 years), so they have emerged as one day experience.
A first observed appeared one after another of the same celestial Halley's Comet in 1705, Newton's friends and donors Harley (1656, 1742) recognize that it is cyclical. Its period is 76 years. The historical record shows that since 240 BC may also come from 466 years BC, through the sun each time it is observed in the. It last passed in 1986. The brightness of the comet far from the sun is low, and its spectrum is simply reflected the sun's spectrum. Comets entering less than astronomical units from the sun eight, its brightness began to grow rapidly, and the spectrum is changing dramatically. Scientists see several bright lines are known molecular. This change occurs because the composition of the comet's solid material (nucleus) suddenly becomes hot enough to evaporation and nucleus surrounded by a cloud of gas called the coma. Caused by the sun's UV luminous gas. Coma diameter is usually about 105 kilometers, but the tail is often very long, up to 108 km or 1 astronomical unit.
Scientists estimate that generally only a few astronomical units of the comet close to the sun distance in thousands of years

The comet strikes (20) to collapse. In 1066, the Norman invasion of Britain on the eve of regression coincided with Halley's Comet. At that time, people had a complex mood, watching the night sky Fengyun strange celestial dragging a long tail, considered to be a war warning given by God and foreshadowing. Later, the Normans conquered Britain, Norman commander's wife when Halley's Comet regression scene embroidered on a tapestry to commemorate. Chinese folk banished the comet known as the "jinx", "bane". The comet appeared and the world of war, famine, flood, pestilence and other disasters linked things like this, there are many Chinese and foreign history. Comet in prolate track (a handful around the sun in a nearly circular orbit) on a quality smaller cloudy Small Bodies

Where comets come from?


In addition to the periodic comet, and constantly open or closed orbit comet visits the inner solar system. New comets come from? This issue will be talked about from the formation of the solar system.
The origin of the solar system:
The predecessor of the solar system, a gas cloud of gas and dust, the cloud may be 4.6 billion years ago, a supernova explosion shock wave compression, start slowly rotating trap shrunk discoid, the center of the disc is young sun. The disk of gas clouds particles collide with each other, there is a considerable ratio of material condensed into planets and their satellites, and another part of the remnants of clouds substances condense into a comet.

When the solar system was young, the comet may be seen everywhere, these comets are often associated with the beginning of the formation of the planets collided with a far-reaching impact on the growth and evolution of young planets. A large amount of water on Earth, may be the heritage of many comets collided with the young Earth, the water and later gave birth to a wide range of life in the Earth.

More than four billion years after the formation of the solar system, comets near the area of ​​the center of the solar system, or collide with the sun, planets and moons, or by evaporation of the solar radiation, has disappeared till the best, we are now seeing the comet from the edge of the solar system . Assuming residual comet material in the outer solar system, after billions of years has not changed, the study of these comets, help to understand the original chemical composition and state of the solar system.


The comet's hometown:
The theory is now widely accepted by astronomers, the big family of the solar system, including the nine planets and the outer Kuiper Belt and the Oort cloud. The long-period comets may come from the Oort cloud and short-period comets from the Kuiper belt.

Oort cloud theory:
In 1950, Dutch astronomer Jan Oort fullerene zone between 30,000 AU A light from the sun, hundreds of trillions of comets exist, these comets residues in the formation of the solar system. Some Oort comet occasionally by passing stars or collisions between each other, apart from the original track. Most-orbiting comet, never entered the large telescopes can detect the distance. Only a small number of comets into the inner solar system, with a wide range of orbital. But so far the the theoretical Oort cloud is only assumed that there is no direct observational evidence.



Kuiper Belt:
Oort cloud theory can be a reasonable interpretation of the arbitrariness of the angle between the source of long-period comets and comet with yellow pavement. Short of the comet's orbit in the orbital plane of the planets in our solar system, the Oort cloud theory can not reasonably answer the origin of short-period comets.

In 1951, the American astronomer Gerard Kuiper proposed a Kuiper Belt between 30 to 100 AU from the Sun (or called the Kuyper belt), to bring many of ice orbiting the sun, these ice orbital plane of the planets similar Occasionally, some of the Kuiper Belt objects by the gravity of the outer planets disturbance and traction, while running to the direction of the sun, crossed the orbit of Neptune, and further influenced by Neptune's gravity, and become short-period comets into the inner solar system.

Astronomer David Jewitt and Jane Luu since 1988, can detect very dim objects, high-sensitivity electronic cameras to find Kuiper Belt objects. They found in 1992, the first such objects (1992 QB1), 1992 QB1 291 years away from the average distance of the sun's 43AU, revolution cycle. Often referred to as Kuiper Belt objects beyond Neptune celestial the (List the Of Transneptunian Objects). 1992-2002, and one after another they found over 600 Kuiper Belt objects (the latest list can be found in the MPC's List Of Transneptunian Objects). At this stage, the astronomers think Pluto, Charon and Triton may have been into the inner solar system's Kuiper Belt Objects, and recently discovered the the melon Alvareaux (Quaoar), its size is about half of the Pluto.

Introduction of Comet


Comets are special objects of the solar system and the majority of their orbit is a parabola, a small number of extremely narrow elliptical or hyperbolic, elliptical orbit of the comet, periodically appear near the sun. However, the long-period comet's orbit and the ecliptic plane any angle between.

Comets want to near from the sun will be found, rarely visible comet opportunity, when the forecast bright comet appeared comet observations of the general public, often provoked boom. About the size of the core of the comet within tens of kilometers, to attract the attention and it is really not a ratio.

Like the brightness of comets such as Comet Hyakutake, an average of every two, three decades a. Predict new is extremely difficult to find the next possible brightness of the comet, and only in accordance with past experience coupled with some imagination, were roughly the comet when the Earth is closest to the possible brightness. Comet Hale-Bopp (April 5, 1996), about seven hundred million kilometers away from Earth or about 5AU, its brightness is about 8.6 magnitude, according to the astronomers estimated luminosity curve development, 22 March 1997 day recently Earth distance, the luminosity of up to 0.4 magnitude, then likely will set off another wave of comet heat. Can see the comet in the Earth's night sky, please refer to the website of Comets and Meteor Showers.

The naming of the comet
Generally comet comet sub growth cycle (long-periodic comet) and short-period comets (long-periodic comet). The cycle is less than 200 years for the short-period comets, most of such comets orbit the same plane of the solar system. Long-period comet's orbit and the angle between the plane of the solar system, to any point of view, such as the angle of Comet Hyakutake is about 124 degrees, the Hale-Bopp comet, an angle of 89 degrees.

Besides named after the discoverer, the scientific name of the long-period comets (proper name) are named according to the year and month of the discovery by the International Astronomical Union (International Astronomical Union). International Astronomical Union annual twelve months subdivided into the first half and the second half of each of the 24 letters of the alphabet except "I" and "Z" calibration, such as Comet Hale-Bopp (a period of about 3,000 years) found On 23 July 1995, and for the second half of the first one discovered comet scientific name C/1995 O1. Comet Hyakutake (a period of about two million years) was found on January 30, 1996, is found in the second half of the second comet called C/1996 B2, it is learned. The short-period comets are often named after the name of the discoverer, such as Halley's Comet (cycle 76), known as P / Halley.



The nature and structure of the comet
Called comets as "dirty snowballs" or "dust ball" are quite appropriate. Comet far from the sun by the solar radiation, evaporation is not yet significant, referred to as the solid part of the comet nucleus (nucleus of), is mainly composed of dust, rocks, ice and condensed into solid ammonia, methane, carbon dioxide, etc. compounds.

The main structure of the comet nucleus, coma and tail. The size of the nucleus, which is normally in the tens of kilometers. The latest microwave radar data show that the the the Hyakutake comet's nucleus surprisingly small, ranging between one kilometer and three kilometers. The nucleus of Halley's Comet in about ten kilometers Schwassman-Wachmann, short-period comets nucleus as much as 40 km.

When the comet near the sun, by irradiation of the sun's light and heat, gas adsorption condensed substances and solid is evaporated, reflecting sunlight air mass formed in the nucleus peripheral called the coma (coma), nucleus and collectively known as the coma of the comet head. At this point, it sizes up to 100,000 km.

When the comet is very close to the sun, coma substances subject to solar radiation and the solar wind took its toll, forcing partial coma substances to deviate from the direction of the sun flowing, long hair-like tail (tail) tail is usually far from the sun, However, It is the Silk Book comet Figure, the shape of the coma and tail were highly variable, and tail can be subdivided into the dust tail (dust tail) and the ion tail (ion tail) in two parts. Tail length of up to several million kilometers or even hundreds of millions of kilometers long.

Tail material is also thinner than the laboratory vacuum, basically on Earth should not have any effect, but if any comet with Earth head-on crash, is another matter. 1908 in mysterious bombings in the forests of central Siberia (Tunguska event), many astronomers believe, is caused by a 50-100 m diameter comet or comet fragment exploded above the forest.