2018-12-06 01:30:51 Source: Science and Technology Daily
Comet Halley visited Earth in 1986. NASA Since December, the Comet 46P has gradually become better and brighter. Photo of Wang Zhuoyu
In December, star photography enthusiasts are getting ready again. In addition to the Gemini meteor shower, they are also looking forward to an "alternative" star – the 46P comet.
Looking at the night sky, the stars and the moon, each one follows his own trajectory and appears regularly in the field of vision of the people. But comets are a special group. They are free between the sun and many planets, in close contact with the Earth for decades or centuries. Every time they appear, they emit a dazzling light, and more, dragging their long tails and swaying through the night sky.
The comet is a celestial body that enters the solar system and whose brightness and shape change with the change of daily distance, presenting a unique appearance in the form of a cloud. The comet is divided into three parts: the nucleus, the scorpion and the tail. The quality and density of comets are very small: when they are far from the sun, they are just a "dirty snowball" made up of frozen ice cubes, such as water, ammonia and methane, and contain many solid particles of dust. When they approach the sun, the comets are undone in hoes and tails under the action of solar radiation, like a broom.
To better identify the comet, each confirmed comet has its own name. Comet is named after the inventor's last name or number. When named with a surname, a comet can only be identified with three discoverers, such as comet "Sumek-Levy 9" in 1994.
If named by number, before 1995, the comets were named according to the order of discovery each year. Since 1995, the International Astronomical Union has adopted a new numbering method in alphabetical order in half a month. The specific method is to remove the letters I and Z, and order the remaining 24 letters, corresponding to 12 months of the year, and then use the numerals 1, 2, 3, etc. to name the comet found within half a month. At the same time, to identify the comet's status, the corresponding letters should be marked later: P for a short-period comet, C for a long-period comet, D for a comet that is no longer returning or has disappeared, and A for a comet that can be an asteroid; X indicates that it is impossible to calculate the comet of the orbit.
In ancient times, as comets were very attractive and shaped in the night sky, the ancients associated some of the great things that happened, especially bad things, with the appearance of comets. The "History of History" has the saying "seven years, the comet is out, seeing the north, seeing the west in May," corresponding to the fact that after the Qin Dynasty succeeded to the throne at the end of the Warring States period, the generals of the meritorious monks died. But the power of this comet is not limited to that. After a while, the comet reappeared, and for half a month it was hung in the sky, and grandmother Xia Jixia, who was in charge of the government, died again. There are more story records like this. Every comet in history is accompanied by several disasters. As it dragged its long tail like a broom, the ancients believed that the nebula was unknown, which would bring bad luck. But with the advancement of science, humans realize that the comet is just a special celestial body around the Japanese movement, has its own return cycle and has nothing to do with the special events of humans.