Meteor shower

  Every year in mid-December, the Gemini meteor shower will be staged in many places around the world. In 2020, the Geminid meteor shower will arrive as scheduled, reaching its peak in the early morning of December 14th, Beijing time. To watch a meteor shower, acquiesce in a beautiful wish when the meteor traverses the sky, and turn the shortness before you into the eternity in your heart. This is the romantic wish of many people.
  Meteor showers have been recorded in many documents both at home and abroad, leaving behind various imaginations and stories. The study of modern astronomy has revealed more secrets of meteor showers.
The earliest recorded meteor shower comes from China

  The record of meteor showers in our country is earlier than other countries. Unearthed from the ancient tombs of the Wei Kingdom in the Warring States Period, “Bamboo Book Chronicles” clearly records a meteor shower event in the Xia Dynasty more than 3000 years ago: “Xia Emperor Gui fifteen years, the stars in the night fell like rain.” “Zuo Zhuan” also has ” On the Xinmao night in the summer of April, the stars are missing, and the stars fall like rain in the night.” The recorded meteor shower occurred in April in the seventh year of Lu Zhuanggong (687 BC), which is the earliest record of the Lyra meteor shower in the world. The expression of meteor shower “stars fall like rain” can be traced in later dynasties, “Tian Guan Shu” and “Astronomical History”. According to expert statistics, there are 180 records related to meteor showers in ancient my country.
  In ancient my country, the appearance of different meteors was given more meanings, the top of which was related to the change of national fortunes, and the bottom of which was related to the people’s livelihood. The trajectory of the meteor, the place where it fell, the time and weather, etc., based on the above-mentioned differences, the good and bad foretelling are also different, but most of the bad omens are far less beautiful and romantic than modern people wishing to the meteor.
  Of course, there are also romantic stories, one of which is hidden in the “Dong Xian Song · Ice Muscle and Bone” by the great writer Su Shi. “Get up and take your hands together, the house is silent, sometimes I see the stars crossing the river.” This is undoubtedly a meteor shower! The romantic scene of the monarch and his beloved consort enjoying the meteor shower in summer night is reproduced in Su Shi’s writings. Based on the information of the time, moon phase, astrology, and time involved in the word, later generations finally infer that it should have occurred on the eighth day of the sixth month of the lunar calendar in 961 AD, that is, July 23 of the Gregorian calendar. This day was the Perseus at that time. When the meteor shower is the biggest.
  In addition to recording meteor showers, the ancients also explored the relationship between meteors in the sky and meteorites underground. In the “Historical Records: Official Book of Heaven”, there is a record of “When a star falls to the ground, the stone is also”. At that time, people already had the basic understanding that a meteor falling on the ground would become a meteorite. In the Song Dynasty in 1064, the famous Chinese scientist Shen Kuo discovered for the first time a meteorite with iron as the main component and accurately recorded it in his book “Mengxi Bi Tan”. This discovery was nearly 800 years earlier than the Europeans.
Mankind has lifted the veil of meteor shower

  When it comes to meteor showers, the scene that emerges in many people’s minds is that countless meteors fall from the sky in a short period of time, like rain. But in fact, most of the meteor showers we have heard of are difficult to show that the stars are raining. It is good to see two or three per minute, of course, except for the famous Leo meteor shower. It is also through the observation of the Leonid meteor shower that modern scientists have initially revealed the connection between the meteor shower and the comet.
  The Leo Meteor Shower occurs in mid-November of each year, and the number of meteors that can be seen in normal years is also very small, but every 33 years, the Lion King “roars” in the night sky to usher in the outbreak of the Leo Meteor Shower, and you can truly appreciate the meteors. Densely across the sky, as brilliant as fireworks. The Leonid meteor shower also has the reputation of being the king of meteor showers.
  The earliest recorded Leonid meteor shower occurred in 902 AD and came from Spanish history books. In my country’s “History of the Old Five Dynasties”, “there are more than a hundred small meteors, and the streams are crossed.” It records the scene of the Leonid meteor shower on October 15, 931 AD. In subsequent ancient books, there are also many wonderful records of the Leonid meteor shower.
  In 1799, German scientist Alexander Humboldt recorded in detail an outbreak of the Leonid meteor shower. At that time, he was on a scientific expedition in South America. Starting at 2:30 in the morning on November 12, Humboldt and his fellow Frenchman Bonplan had the honor to witness the gorgeous performance in the night sky: thousands of fireballs and falling stars one after another It kept falling from the sky and enveloped the entire night sky. This meteor burst lasted for 4 hours, and it gradually stopped until dawn. This is also the first scientific record of the Leonid meteor shower. Humboldt later discussed the magical sights he saw with the local indigenous people, knowing that such similar phenomena had been periodically observed in the past. Humboldt mentioned scientifically in his report that the cycle of the Leonid meteor shower is about 30 years. He also pointed out that the meteor shower appeared almost from the same place in the sky, and speculated that the next time it should happen in the early 1830s.
  On November 12, 1833, the Leonid meteor shower ushered in another outbreak. It is estimated that 240,000 meteors pierced the sky within 9 hours. In many parts of North America, people have witnessed this unprecedented meteor shower. Many people were caught in their dreams. The noisy crowd watching the shooting stars on the street awakened, and for a moment they couldn’t tell whether it was a dream or reality. In the United States, Yale University mathematician Olmsted noticed the phenomenon of meteors radiating from the same direction, and tried to measure the position of the meteor radiant point in the sky, and found that the rate at which the meteor radiant point moves in the sky, and the star The speed of the earth’s rotation is the same. Later, he and another scientist, Twining, confirmed that the radiant point was near the constellation Leo, and named it the Leonid meteor shower. People began to accept the view that meteor showers came from outside the earth, and the study of meteor showers has officially entered the scientific research category of astronomy. The German astronomer Olbers collected and analyzed previous observations from various countries and found that the Leonid meteor shower erupts every 33 years or so.
  In early 1866, the faint Comet Temple-Tuttle was discovered, and its orbital period around the sun was calculated to be 33 years; in November of the same year, the Leonid meteor shower broke out again. Although it was not as spectacular as 33 years ago, it confirmed the previous predictions. The Leonid meteor shower erupts once in 33 years, and the orbit of the meteor is strikingly similar to the orbit of the comet. Almost at the same time, Italian astronomer Schiaparelli calculated that the Perseid meteor shower should be related to the Great Comet Swift Tuttle discovered in 1862. The little secret between the meteor shower and the comet was discovered by clever humans, and people began to associate the occurrence of the Leonid meteor shower with the Comet Temple-Tuttle.
  In the subsequent 33-year cycle, the Leonid meteor shower sometimes erupts and sometimes converges. People are aware of the influence of Jupiter, Saturn and other celestial bodies on the orbit of the comet, which will lead to the difference in the number and position of the meteoroids scattered in the orbit. The cycle of the Lion King’s roar once in 33 years has become less accurate, and by introducing more analysis conditions, the prediction of the Leo meteor shower’s outbreak is also more accurate. The two Leo meteor showers in 1998 and 2001 predicted by the revised model have allowed tens of millions of people around the world to enjoy the spectacular scenes, which still impress many astronomy enthusiasts born in the 70s and 80s.
Is the meteor shower really related to constellations?

  With the deepening of astronomical observation and research, people have a clearer and more comprehensive understanding of meteor showers.
  There are many speculations about the cause of the meteor shower. There is a theory that it is the result of certain substances on the ground being irradiated by the sun and rising into the atmosphere and burning; there are also views that it is a phenomenon caused by the refraction of the sun’s afterglow in the night sky .
  By the 19th century, with the deepening of research, the astronomy community had a general consensus on its cause. It is generally believed that the production of meteor showers is the result of friction between “meteoroids” and the earth’s atmosphere. The meteoroids here are actually all kinds of dust and solid masses floating around the earth’s orbit around the sun. Many of them are smaller than sand grains. Most of them come from another type of celestial body we are familiar with-comets.

Meteor orbit. Screenshot of the International Meteor Organization (IMO) website.

  The comet is mainly composed of ice and dust. It is vividly compared to a group of “dirty snowballs” full of dust particles. When a comet orbits the sun, it will continuously evaporate and throw out dust particles carried by itself under the influence of temperature and solar wind, which will be scattered on the orbit of the comet, forming a dust ring. If the earth passes through the orbit of this comet, the gravity of the earth will attract a large amount of scattered dust into the earth’s atmosphere, and then it will rub against the atmosphere to form a meteor shower. Because the earth revolves, it meets the orbit of the comet every other year, so meteor showers occur at approximately the same time period each year.
  When a meteor shower appears, if you observe carefully, you will notice that all the meteors are emitted from a specific point in the sky. This point is called the radiant point of the meteor shower. The meteor shower is named after which constellation the radiant point is located in, so the meteor shower with the radiant point in Leo is called the Leo meteor shower. If two meteor showers appear in the same constellation, they are named after the bright stars near the radiant point, such as η Aquarius and δ Aquarius. In fact, meteoroids all fly parallel to the earth, but due to perspective, it seems to fly from a radiant point from the earth, so in essence, meteor showers have nothing to do with constellations.
  Meteor bodies enter the atmosphere at a high speed of 11 to 72 kilometers per second, rubbing with the air to generate heat, and begin to burn and glow at an altitude of 80 to 120 kilometers from the surface. Generally speaking, most meteoroids smaller than sand grains will only flash for one or two seconds; while the massive and fast meteoroids produce higher energy and brighter meteors, such as those that can produce dazzling light. The bolide may continue to glow for a few seconds, or even more than 10 seconds, during which it will shatter and explode several times, and even the sound can be heard. It is still bright enough to be visible to the naked eye when it falls to a height of much lower than 80 kilometers. , And the part that cannot be completely burnt up in the end becomes a meteorite when it falls on the ground.
  Through continuous observation and research accumulation, scientists have counted dozens of large and small meteor showers, which can be found on the International Meteor Organization (IMO) website. The activity cycle of each meteor shower is about dozens of days, which can cover the whole year. , So in fact there are meteor showers every day, and sometimes several meteor showers are staged at the same time in one night. However, most of the meteors that can be seen here are still far below expectations.
  Astronomy usually uses the hourly zenith flow (ZHR) at the peak of the meteor shower to indicate the number of meteors that can be seen. Here ZHR is a popular understanding, that is, when the weather, lighting environment, human vision and other aspects are in the best conditions, the meteor shower radiant point is directly above the head, and how many meteors can be seen every hour. The actual observed numbers are much less than the theoretical ZHR. Many meteor showers have a ZHR value of less than 10. In other words, many meteor showers reported in the news can actually only see a few meteors at most in an hour.
  But there is no need to be discouraged. As we are in the northern hemisphere, there are still 3 meteor showers to look forward to in a year, and their ZHR values ​​are all above 100. They are the Quadrantid meteor shower around January 4, the Perseid meteor shower around August 13, and the upcoming Gemini meteor shower around December 14.