The Gemini meteor shower comes in mid-December every year and this year will reach its maximum between the evening of the 13th and the early morning of the 14th.
"Take you to see the meteor shower, fall on this earth, let your tears fall on my shoulders", twenty years ago, the theme song of the TV series "Meteor Garden" spread throughout the streets. Watching the meteor shower together has become the romantic dream of many young boys and girls. Do you know anything hardcore about meteor showers?
Written by | Li Mingtao
01
What are the relationships between meteors, meteor showers and meteor storms?
Our solar system is a big family. In addition to the sun, the eight planets and their moons, and dwarf planets, there are also a vast sea of small dots - asteroids and comets, smaller micrometeroids, and micron-sized cosmic dust.
Earth, asteroids, comets, micrometeroids, and cosmic dust all orbit the Sun, and their orbits intersect. If they met at the same time and in the same place, they would cause a solar system "traffic accident."
Comets are dirty snowballs made of water ice and rock that generally disintegrate in the atmosphere. Asteroids are mainly made of solid rock, and asteroids over 100 meters in diameter usually pass directly through the atmosphere and reach the Earth's surface, creating impact craters and accompanied by catastrophic phenomena such as strong shock waves, thermal radiation, earthquakes and tsunamis. Small asteroids disintegrate in the atmosphere, explode, and form bright fireballs accompanied by rumbling explosions.
Basic Concepts / American Meteor Society
Meteors are micrometers of millimeter to centimeter size that enter the atmosphere at high speed, squeeze and rub the atmosphere to cause the asteroid surface temperature to rise, and ablation causes luminescence. Most meteors disintegrate at an altitude of 80-120 km and are not accompanied by sound.
Meteor shower / breezyscroll.com
Meteor showers are swarms of meteors that meet Earth. A large number of meteors are seen bursting and falling from a certain point in the night sky, which is also known as a meteor shower radiation point, usually named after the constellation of the celestial area where the meteor shower radiation point is located. For example, leo meteor shower, Perseus meteor shower and so on. When a meteor shower exceeds a certain intensity (such as more than 1,000 meteors per hour at the zenith), it can be called a meteor storm.
02
Where did the meteor shower come from?
Meteor showers are generally parent to comets, but there are also meteor showers that are parent to asteroids.
Comets are dirty snowballs of water ice and gravel. When close to the Sun, sublimated water ice carries grit off the comet's surface. With the use of gravitational and light pressure and other disturbances, the grit gradually spreads over the comet's orbit, forming an elliptical band full of grit. When the Earth passes through this gravel belt, a meteor shower occurs.
Earth passes through the comet's orbit / skyandtelescope.org
The parent body of the Gemini meteor shower is the 3200 Phaethon asteroid. Why asteroids became the parent of meteor showers has not been fully explained. One explanation is that the 3200 Phaethon asteroid may have experienced a serious solar system "traffic accident" a long time ago, resulting in a large amount of sputtering, scattered across orbit.
3200 Phaethon asteroid orbit / earthsky.org
In addition, the 3200 Phaethon asteroid is one of the closest asteroids to the Sun at perihelion, with a closest distance of only about 29 million kilometers, twice as close as Mercury to the Sun. Vaporized by sunlight, the 3200 Phaethon asteroid appears with a small dust tail as it approaches the Sun.
03
What are some of the world's most famous meteor showers?
The Quadrant Meteor Shower, Perseus Meteor Shower and Gemini Meteor Shower are known as the three major meteor showers in the Northern Hemisphere, with more than 100 zenith meteors per hour.
Meteor Shower Time and Matrix / NASA
The Leo meteor shower is also the famous "king of the meteor shower". Its intensity shows obvious cyclical characteristics, meteor showers are usually less intense, about 10 to 15 meteors per hour, but on average, every 33 to 34 years, the Leo meteor shower will appear a peak period, the number of meteors can exceed thousands of meteors per hour, forming a meteor storm.
In 1883, the Leo meteor shower ushered in a super explosive explosion, setting a record for the intensity of 100,000 meteors per hour, making the Leo meteor shower gain the reputation of "king of meteor showers".
Leo Meteor Shower Super Eruption of 1883 / Adolf Vollmy
The Leo meteor shower last erupted around 2001, and according to post-mortem statistics, nearly 9,000 meteors per hour streaked across the sky at its climax. The next outbreak of the Leo meteor shower is expected around 2034.
04
What colors are meteors?
If you are careful, you may find that meteors have different colors, what is the difference between different colored meteors? In fact, the color of the meteor is the embodiment of the chemical composition and reaction temperature of the meteor body, and the meteors of different compositions will show different colors when they pass through the atmosphere.
Meteor color with material composition / ALMA
The main components of meteoroids are calcium, magnesium, sodium, iron, silicon and other elements. Different elements emit different wavelengths of light when ablated. For example, calcium atoms produce purple light; magnesium atoms emit blue-green light; sodium atoms emit orange light; iron atoms emit yellow light; silicon atoms emit red light. The numerous nitrogen and oxygen atoms in the air emit a red light.
The color of the meteor is also related to the ablation temperature. Many meteors tend to drag a green tail in their initial stages, corresponding to the emission lines of oxygen atoms in the upper atmosphere. As the temperature increases, the meteor body is more ablated, and gradually shows the emission spectral characteristics of the meteor body material. The ablation temperatures of different material components are different, which further increases the complexity of the meteor spectrum.
05
Will meteor showers endanger astronaut safety?
The chances of a space station being hit by a meteor are very low, but that doesn't mean there's no possibility.
Olympus 1 was an ESA communications satellite in the 1980s and was the largest civilian communications satellite ever built at the time. At the peak of the Perseid meteor shower from August 11 to 12, 1993, the moon lost control of its attitude and began to rotate. It is speculated that it was hit and damaged by fragments of Comet Swift-Tuttle (109P/Swift-Tuttle). Eventually, the Olympus satellite was sent to a "satellite dump" – GEO discarded orbit.
Olympus 1 Communications Satellite/ESA
When choosing a space launch window, try to avoid the peak moment of the meteor shower. From 1997 to 2002, during the 33-year return period of the Leo meteor shower, comet Tempel-Tuttle, the parent of this famous meteor shower, returned to the perihelion, and because it was very close to the Earth's orbit, the meteoroid particles gathered before and after the comet were sprayed towards the Earth at high speed, producing a meteor storm far beyond usual. Spacecraft launched or operated during this period will have to consider the impact that may come from meteor bursts. Experts from the Space Environment Forecasting Center of the Chinese Academy of Sciences predicted that the Shenzhou-1 spacecraft was scheduled to launch at 7:00 Beijing time on November 18, 1998, coinciding with the peak of the Leo meteor storm, and the 7:00 meteor storm on November 20, 2 days later, had ended.
Shenzhou I launch / network
At that time, Gu Yidong, the chief designer of the spacecraft application system, asked what was the probability of encountering a meteor shower on the 18th. Gong Jiancun, director of the Space Environment Forecast Center, said that the risk of launching on the 18th was 100%. Delayed for 24 hours, the risk is 6%. Delayed for 48 hours, the risk is near zero. According to this, they suggested that the launch of the spacecraft be postponed by 2 days to ensure the safe operation of Shenzhou-1.
06
Does the meteor shower have to happen at night?
No, there are also meteor showers during the day.
It's just that the light is too strong during the day, and people usually can't see the meteor shower that occurs during the day. Modern scientists, with the help of facilities such as meteor radar, have been able to study meteor showers that occur during the day.
Sextantids meteor showers occur during the day and peak around September 27 each year. Because it occurs during the day, the hexapon meteor shower has a radiation point very close to the Sun and is one of the most difficult meteor showers to observe. Goggles are required to observe the sextant meteor shower, otherwise the eyes may be harmed by the dazzling sunlight. It is also possible to observe the Sextant Meteor Shower before sunrise, with the best time to observe it at 4:30 a.m.
Daytime meteor captured by NASA's all-sky fireball net/NASA
07
Did the ancients ever see a meteor shower?
Yes, the ancients not only saw meteor showers, but also made detailed records.
China was the first country to record meteor showers. In the "Bamboo Book Chronicle", there is a record of "the fifteenth year of the Xia Emperor, and the stars in the night are like rain". In the "Left Biography", there is a statement that "in the summer of April, the stars are not seen, and the stars in the night are like rain", and the recorded meteor shower occurred in April of the seventh year of luzhuang (687 BC), which is the earliest record of the Lyra meteor shower in the world.
The Left Biography about the Lyra Meteor Shower / Network
According to expert statistics, there are as many as 180 records related to meteor showers in ancient China. Among them, about 9 Lyra meteor showers have been recorded, about 12 Perseid meteor showers, and 7 Times have been recorded leo meteor showers.
Regarding the moving scene of the meteor shower, the ancient Chinese record is also wonderful. During the Southern and Northern Dynasties, Emperor Xiaowu of the Liu Song Dynasty "In March of the fifth year of the Ming Dynasty, the moon covered Xuanyuan. There are tens of millions of meteors, long or short, large or small, and travel west until dawn. ”
About the Author
Li Mingtao, a researcher at the National Space Science Center of the Chinese Academy of Sciences, is mainly engaged in the research of artificial/natural celestial orbit mechanics, planetary defense and utilization, and does planetary defense science in his spare time.
This article is reprinted with permission from the WeChat public account "China National Astronomy", the original title is "When we look at the meteor shower, you want to know seven things", edited by: Huai Chen, Zi Xiao.