Shulou(Shulou.com)11/24 Report--

A few days ago, Xiao Mu discovered this news while surfing:

The report uses the West five time zone, where the meteor finally fell, that is, 04:27 in the morning, but this did not prevent me from sitting upright.

This made me sit up when I was lying flat and fishing. Because it is not well known that an asteroid and a meteor are actually the same thing, except that the meteor was burned by atmospheric friction before falling to the ground, and the 0.7m-long asteroid 2022 WJ1 held on to the last minute, overcoming resistance and smashing it down. When I think of my previous experience of watching a meteor shower, if a big meteor (or asteroid) was scratched down when I made a wish, it would have realized my dream of going to heaven.

In view of the fact that asteroids, meteors and meteorites are actually different names for the same thing, I will blur the difference between them later. Please distinguish them when you read.

Fortunately, the meteor injury incident caused no casualties in the end. According to follow-up reports [1], it did not fall in its entirety, but disintegrated as it rubbed against the atmosphere, and eventually exploded over Lake Ontario. Most of the fragments were spilled into the lake, and only a few fell on the uninhabited lake.

In addition, the asteroid was discovered by the Katarina Sky Survey system in the United States three hours before the impact. An hour later, the system confirmed that its trajectory would hit Lake Ontario, but it was small and did not pose a threat. Subsequently, Richard, chief operating expert of Katarina systems, announced the news. In other words, local astronomy enthusiasts (and awake at 02:30 in the morning) knew in advance that there would be such an alien and were ready to film it.

Well, the main idea of the title is that someone photographed a super gorgeous meteor over Toronto, Canada. Meteor should mean meteor, so the local people will not feel that this is a "heavenly hindrance shock star".

The asteroid enters the atmosphere at an angle of only 10 degrees, close to the level, and can drag out a long meteor trajectory, with sufficient distance to be rubbed and ablated. By contrast, in 2013, Russia's Chelyabinsk region hit an 18-meter-diameter asteroid, injuring nearly 1500 people. Fortunately, all the injuries were caused by the shock wave generated when the meteorite fell to the ground, and no one was hit by the meteorite debris.

In the Chelyabinsk incident, "inside the car" is part of the place name, not from the perspective of this dynamic picture. In fact, asteroids hit the earth in the car. Although the universe looks empty, it is also full of small celestial bodies. Some agencies estimate that 50 asteroids fall into the earth every day, but it is rare for an asteroid to hit the earth with a diameter of up to a meter. Such asteroids tend to stand out, but smaller ones may have evaporated in the atmosphere before they can be seen. Therefore, the present years are quiet and good, and there is an atmosphere carrying heavy loads for us. However, we can not rely entirely on the protection of the atmosphere, including Katarina, there are already a number of sky survey programs to monitor potentially threatening asteroids, and there are special agencies to predict this.

Asteroid impact hazard and average impact interval | quoted from [1], data source the United States National Strategic Planning and response Plan for near-Earth objects. I checked online to see if there were any people who were unfortunately hit by meteors in history. I found that in the bright history of thousands of years of civilization, there is indeed a tragedy of meteor injury. For example, in 1888, a meteorite fell in the present-day Sulaymaniyah region of Iraq, killing one person and paralyzing another. This is by far the earliest documented meteor injury incident. For example, in 1954, while Ms. Anne Hodges was taking a nap at home, a meteorite falling from the sky smashed through the roof, hit the radio and bounced back to her waist. (for example, in 2011, Ms. Xu Lun was injured by a meteorite during a fight with a cellmate in Green Dolphin Prison; or in the 12th year of the crisis, three veteran scientists, Zhang Dajun, Liu Pei and Mo Qiang, were killed by a 7.62 mm meteorite while taking photos in outer space.)

Ahem, the parentheses above are all fictional characters | Source: "the wonderful Adventure Stone Sea of JoJo", "my three-body Biography of the North Sea" No.5, so this time let's talk about meteors and other ways of "moving" stars.

Starting with comets, the story starts with the birth of the solar system. At that time, there was only a cloud of interstellar dust in space, which itself had a certain initial velocity. Under the action of gravity and collision, most of them collapse into the sun and are lucky to have the conditions to ignite nuclear fusion, bringing light and heat to this side of the world. A small part of the dust becomes planets and moons, rotating and rotating at initial velocity and gravity. In this part, there is a special kind of celestial body, which is a "dirty snowball" away from the sun most of the time, which is composed of frozen ice cubes such as water, ammonia and methane mixed with many solid dust particles. It will come near the sun and evaporate under the action of the sun, pulling out a long tail of the comet.

The elliptical orbit of Halley's comet, whose circles from outside to inside are Neptune, Uranus, Saturn, Jupiter and so on, is the famous Halley's comet. Its trajectory is a very flat ellipse with a revolution period of about 76 years. As early as 613 BC, it was recorded in Spring and Autumn that "in Autumn and July, stars enter the Beidou". In 1682, Edmund Harley, a 26-year-old Englishman, was excited when he observed a comet under Cassini's guidance. Two years later, he visited Newton at Cambridge University to study Newtonian mechanics, and compared with previous ephemeris, he calculated in 1705 that the comet would return about every 76 years. Unfortunately, he did not have the opportunity to witness his return in 1758. But when the comet did return that year, people excitedly named it Harley.

An easy misconception about the orientation of a comet's tail is that a comet's tail is pointing back to the sun, not to its orbit. Because the comet tail is mainly blown out by the sun's light pressure and solar ion wind, rather than by its own rotation, the comet tail appears only when it is close to the sun. This phenomenon also supports that light has momentum and can produce light pressure.

The tail of Halley's Comet sometimes you will see that a comet has two tails, a gas tail and a dust tail. After sublimation, small molecules such as water are easily ionized by the solar wind to produce ionic gas, which is lighter and will be blown out directly by the sun's light pressure and solar wind to form a gas tail; other dust is not easy to be ionized and has a larger mass. Solar light pressure and solar wind have less influence on it, so it is blown away more slowly, pulling out a curved dust tail. Generally speaking, the gas tail will glow and appear blue, while the dust tail can only reflect light, but it will appear brighter in more quantities.

Gas tail, dust tail and dust track it's time to talk about meteors. Remember in the picture above, I didn't talk about Dust trail (dust track)? That's the little dust that the comet left in its orbit, and it spreads around the comet's orbit, like the dandruff left on the track by an athlete while running, tiny, but all over the runway.

Dust tracks of Halley's comet meteors | Source: Meteor showers from space or take Halley's comet as an example, when the earth rotates to late October and early May, it will converge with these dust tracks. Considering the velocity of the dust itself in orbit, minus the earth's rotational speed, the relative velocity directions point to Orion and Aquarius, respectively, giving birth to the Orionid meteor shower and the Aquarius η meteor shower.

In other words, meteor showers are formed by dust left over from the Earth's orbit of comets. Their sources all seem to point in the same direction, and the constellation where the radiation center is located becomes the name of the meteor shower.

Earth sucks up dust in the dust belt of the Leonid meteor shower, leaving a clean zone | Jenniskens (2006), p. 233 however, not all comets' orbits are almost coplanar with Earth's orbits, and in most cases the two have a considerable inclination. Comets' orbits meet only at one point with the Earth, resulting in only one meteor shower.

Time and flow of major meteor showers | data sources: ZHR (Zenithal Hourly Rate) in Astronomical, American Meteor Society and Wikipedia tables is the hourly occurrence rate of the zenith, which means the number of meteors that can be seen per hour when the radiation point is at the zenith. After understanding this, we can happily set off to see the meteors. Choose a meteor shower day, avoid the full moon, choose a place where the light pollution is not so serious, and make a travel plan, let's go!

On the light pollution map of Beijing, I chose the northernmost Laobagoumen | Source: darkmap.cn combines all the places where meteors appear, and becomes:

Compared with the Stellarium starry sky simulation software, we can see that most meteors do point to Orion.

Luckily, this year's ZHR peaked at 40, the highest in nearly three years.

The color of meteors is also very particular. For example, orange yellow represents sodium, purple represents calcium, red represents nitrogen and oxygen in the atmosphere, and so on. Here, borrowing a picture of teacher Zhang Chao [5], you can see that the meteor in the picture is divided into two segments. The green on the left is the 557.7nm line of oxygen in the atmosphere, and the turquoise on the right represents that the meteor contains magnesium.

Two green lights | Source: Zhang Chao has a lot to say about the color of meteors. Readers who are interested can go to the reference [5] to expand their reading.

If you talk about lunar eclipses, astronomical readers will remember that on November 8, that is, half a month ago, nature staged a feast of total lunar eclipse + Uranus.

Xiao Mu, as an astronomical enthusiast, naturally did not miss this opportunity and took such a picture in his spare time.

Look carefully at the lower left corner of the moon from 18:45 to 19:21. That is Uranus.

Take out the Stellarium simulation again, and it is true that Uranus is eclipsed by the moon.

Fixed ground viewing angle

Fixed Uranus perspective some readers may ask, why does the moon in the earth's shadow look red? This is because, although the earth blocks the sunlight shining on the moon, the earth's atmosphere scatters sunlight, and short-wavelength light such as blue light is more likely to be scattered (that is, the blue sky we see), and the remaining red light is refracted into the shadow. to form a red moon.

The formation of the red moon | Image source: timeanddate on the contrary, because the moon has almost no atmosphere, its shadow is black during a solar eclipse.

Lunar shadow of solar eclipse | Source: Wikipedia theoretically, a lunar eclipse occurs when the sun, the earth and the moon are collinear at three o'clock. Since there is an angle of about 5 °between the white plane of the moon and the ecliptic plane of the sun, this situation will only occur twice a year, but more than half of it is a partial lunar eclipse, and the total lunar eclipse visible in China will be less than half. The same is true of solar eclipses. For more information, please go to reference [6] to see the solar and lunar eclipse calendar.

Three-dimensional schematic diagram of lunar eclipse | timeanddate for example, there is also a lunar eclipse on May 16 this year, but it occurs between 9:32 and 14:50 Beijing time. At that time, we were in an area facing the sun and back to the moon, so we couldn't see it.

For the lunar eclipse on May 16 this year, the color from light to deep is daytime, and the moon is high in the night sky at 0: 6 °, 6: 12 °, 12: 18 °. Image source: timeanddate will also have a lunar eclipse on May 6 next year. Although it is visible in China, the penumbra lunar eclipse will only be darker than usual and there will be no red moon.

Occultation and other movements of the planets one of the highlights of this eclipse is that the moon obscures Uranus for a period of time in this shadow, when the moon is not very bright, so it is easier to see Uranus. Online enthusiasts have successfully photographed Uranus next to the moon with binoculars showing a turquoise color.

Speaking of which, the 10th question of the common sense judgment of the 2017 national examination got the occultation:

Common sense judgment part

Exam rules: click on the option you think is correct

10. Occultation is an astronomical phenomenon that occurs when one celestial body passes between another celestial body and the observer. Scientists often observe this phenomenon to determine whether a star has an atmosphere. When the planet obscures the distant star, if the star becomes blurred before it disappears, then it can be considered ()

a. The star has a dense atmosphere

Correct answer, √.

Analysis: the star is blurred at first because the atmosphere on the surface of the planet first obscures the star. although the atmosphere is transparent, it will scatter and reflect light, making the planet blurred. Then the planet completely obscures the star and the star disappears.

b. The star has a dense atmosphere

Wrong answer ✕

c. The planet has no atmosphere or thin atmosphere

Wrong answer ✕

d. The star has no atmosphere or thin atmosphere

Wrong answer ✕

Stars are blurred at first because the atmosphere on the surface of the planet first obscures the star. although the atmosphere is transparent, it scatters and reflects light, blurring the planet. Then the planet completely obscures the star and the star disappears. So we choose A.

The opposite of occultation is the transiting star, but we generally use the word "transit" more often. Occultation is a larger star masking a smaller star, while a transiting star is a smaller star masking a larger star. For the first time in history, Harley proposed to use the transit of Venus to measure the distance between the sun and the earth, and this method does get quite accurate values. At present, transits are also the main means of discovering exoplanets. One of the winners of the Nobel Prize in Physics in 2019 is to detect exoplanets with changes in the brightness of stars during transiting stars.

Well, since we are all talking about the transit, let's talk about Chongri again. The transit is for the planets on the inside of the earth, it occurs at the confluence, and the sunburst is for the planets outside the earth, which is the brightest on the earth, not only because the earth is closer to it, but also because it faces the sun, similar to the full moon of the moon. So sunstroke is the best time to observe extraterrestrial planets, especially distant planets in the Kuiper belt.

The relative relationship between the positions of inner and outer planets | Wikipedia, now that we are all on this picture, let's go over all the positional relationships. Let's take a look at the extraterrestrial planets, which have just been introduced to the sun. "Oriental illumination" and "western illumination" correspond to positions perpendicular to the direction of the sun, and "he" corresponds to positions on the same side of the sun.

For the inner planet, there is no such thing as going into the sun, and it is impossible to reach the opposite side of the sun. Its azimuth is called "large distance" when it is farthest from the sun, and this is also the best time to observe it. The inner planet lies in the east of the sun and sets later than the sun at dusk, while the inner planet lies in the west of the sun and rises earlier than the sun in the early morning. From the Earth's point of view, when the local inner planet moves behind the sun, it is called "upper closure" and when it is in front of the sun it is called "lower closure". The inner planets are divided into morning stars and evening stars.

Like a lunar eclipse, transits do not occur every time the inner planets meet. This is because the orbits of Mercury and Venus are at an angle of 7 °and 3.4 °to the ecliptic, respectively. Venus, for example, did not skim across the sun in 2020 and 1996.

"Venus naughty" | Source: compared with Venus, Mercury is closer to the sun, shorter orbit period and shorter rendezvous period, so Mercury transit is more likely to occur. The next transit of Mercury will be from 3: 00 p.m. to 7: 00 p.m. on November 13, 2032. Let's meet ten years later.

Reference:

[1] are you ready to face the threat of near-Earth objects when another asteroid hits the earth?

[2] the first meteorite record: "starry rain" in 1888, killing one person and paralyzing another.

[3] We Have The First-Ever Credible Evidence of Someone Killed by a Falling Meteorite: ScienceAlert

[4] Unsalan, O., Bayatl trees, A. and Jenniskens, P. (2020), Earliest evidence of a death and injury by a meteorite. Meteorit Planet Sci, 55: 88689.

[5] do you know the secret of meteor color?

[6] Solar and Lunar Eclipses Worldwide

This article comes from the official account of Wechat: Institute of Physics, Chinese Academy of Sciences (ID:cas-iop), author: Xiao Mu, Editor: Mu Zi

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