Chapter 156 Myth from Beyond (6.6K)
Astronomy enthusiasts should know this.
The so-called supernova explosion.
It refers to a violent explosion that some stars experience when they are near the end of their evolution.
These explosions are extremely bright, and the bursts of electromagnetic radiation often illuminate the entire galaxy in which they are located.
It can last for weeks to months before gradually fading and becoming invisible.
During this period.
The energy radiated by a supernova is comparable to the total energy radiated by the sun in its lifetime.
But on the other hand.
Although a supernova explosion is an extremely dazzling spectacle in the universe, it is magnificent, beautiful and intoxicating.
But for humans, this is actually a risky thing.
During the explosion of a supernova, a large amount of gamma rays are released, which radiate into the Earth's atmosphere at the speed of light.
Gamma rays trigger a special chemical reaction after contacting the atmosphere:
They convert nitrogen molecules into nitrogen oxide.
This depletes the protective umbrella of life on earth, the ozone layer.
As a result, life on earth is directly exposed to harmful radiation such as solar wind and cosmic rays.
For example, there have been five mass extinction events in the history of life on Earth, with the Ordovician mass extinction ranking second.
The Ordovician mass extinction occurred 440 million years ago, which led to the extinction of 85% of the earth's species at that time, and later triggered an ice age.
And in 2005.
NASA and the University of Kansas jointly released a research report.
The report believes that this mass extinction event was probably caused by a gamma ray burst released by a supernova.
The situation restored according to the model.
The entire process may have lasted only ten seconds, but it destroyed half of the earth's ozone layer.
In the end, the sun's ultraviolet rays hit the earth, causing the death of a large number of organisms on the surface, thus causing a mass extinction of organisms. (doi.org/10.1099/ijs.0.02503-0)
By the way.
Currently, Betelgeuse is the subject of much discussion in the astronomical community. Its recent photometry data are somewhat abnormal, and it may cause a supernova explosion.
But due to the distance, this thing will not have any impact on life on earth.
After all, radiation also requires basic physical rules.
Except for Betelgeuse.
Another star that may undergo a superexplosion is WR102 in the constellation Sagittarius.
It is a very rare oxygen-rich Wolf-Rayet star. According to existing models, it is highly likely that this star has exploded.
Infer based on distance.
As long as you live 1500-2000 more years, you should be able to see this beautiful scenery, it's not too difficult
all in all.
In the past two thousand years, humans have observed a total of eight supernova explosions.
There are also many of the best:
For example, the earliest supernova record was SN185 seen by local astronomers in 185 AD.
Another example is that the brightest supernova on record is SN1006.
Supernovae SN1572 and SN1604 were the last two Milky Way supernovae observed with the naked eye and had a significant impact on the development of European astronomy.
Because they were used to refute the Aristotelian universe that was unchanging beyond the moon and planets, they were landmark discoveries.
Wait until the age of telescopes.
Humans have successively observed SN1885A, SN1987A and SN2006gy.
Of course.
Saw this.
Students who failed math must have discovered a problem:
Obviously there are eight supernova explosions, why are only seven mentioned above?
That's right.
The remaining supernova explosion was the Crab Nebula super explosion that Lao Su personally experienced in 1054 AD.
at the same time.
It is also the most widely observed supernova explosion in human history.
It is about 6,500 light years away from the earth, which means that the scene we see now is what happened 6,500 years ago.
Analysis of historical records shows.
The supernova that produced the Crab Nebula occurred in April or early May, and at its brightest in July, the apparent magnitude rose to between -7 and -4.5.
During that time, it is brighter than any object in the night sky except the Moon.
This wonder even lasted into the 21st century:
At that time, the Crab Nebula still had a large number of oval filament-like structures surrounding a diffuse blue core region in the visible light region.
It is 6 cents long and 4 cents wide.
It is one of the celestial objects with the largest apparent diameter.
Of course.
It is also the most beautiful celestial body. (If you are interested, you can search it. It is really beautiful. Friends who have the opportunity to go to the Magic City can buy a planetarium ticket for 60, which is absolutely worth it)
However, compared with the first time he observed the moon, Xu Yun did not do it himself this time.
Instead, he let Lao Su try it himself.
Still the same sentence.
It is better to teach people to fish than to teach them to fish. If you just instill knowledge blindly, everything will return to the original state after you leave.
"Yes, yes, yes, turn the finder first, wait, it's passed."
"The cross hairs are closer together"
Looking at Lao Su tinkering with the equipment, Xu Yun seemed very patient.
After all, compared with those few readers in his previous life, Lao Su was simply a model of learning.
After a while.
Seeing that Lao Su was almost ready, Xu Yun asked:
"Master, can you recognize the direction of Bisu?"
Lao Su nodded without much hesitation this time and said:
"Bisu, one of the twenty-eight places, the fifth place of the White Tiger of the West.
This star position is marked in the star chart written by me. ”
Bisu is also called Biyuewu.
It consists of eight stars and is one of the ancient Chinese star officials.
The origin of Bisu is actually very simple:
Its eight stars combined together resemble a "Y" shape. The ancients believed that its appearance is very similar to "Bi", a long-handled tool used to capture small animals.
So it was passed down from generation to generation and was named Bisu.
Of course.
There is also a more intuitive illustration - have you ever seen a fork that moistens soil?
Yes, that's it.
In modern astronomy, Aldea is located in the constellation Taurus, adjacent to the Pleiades.
Among them, Aldebaran has a diameter of about 53 million kilometers, which is 38 times the diameter of the sun, and its brightness is extremely conspicuous.
On October 19, 2005, there was an astronomical spectacle of Aldebaran and the moon competing in the starry sky.
At that time, in many small places, you could see many "profiteers" who set up telescopes on the streets to trick children into looking at the stars, and they paid ten yuan a time.
Nowadays, many of the big guys in the industry who drive off-road vehicles and pull hundreds of thousands or millions of astronomical telescopes rely on that method to complete their primitive accumulation.
His gaze returned to its original position.
As the person most familiar with star maps in the contemporary era, Lao Su quickly locked onto Bisu's area after receiving Xu Yun's guidance.
Xu Yunjian continued:
"Sir, if I remember correctly, the supernova is northeast of Aldebara."
Upon hearing this, Lao Su quickly locked his eyes on the finderscope, twisted the screws, and continued to calibrate.
Looking at Lao Su who had gradually become familiar with the operation, Xu Yun wanted to say to his classmates in his previous life, "Look at Lao Su."
Of course.
At that time, those sexy readers will most likely cut off the starting strength list, and Aite will counterattack by himself - "Look at this eagle!".
Tentacle monsters deserve to die.jpg.
that's all.
After a while.
Lao Su's expression suddenly shook, and he waved towards Xu Yun with his left hand:
"Xiao Wang, come and take a look, is this star, or is this thing the Crab Nebula?"
Xu Yun quickly stepped forward.
I only see this moment.
Within the field of view of the starfinder in front of Lao Su, a small white light group with high brightness could be vaguely seen.
Xu Yun was very familiar with the shape of this light group, so he nodded immediately and said:
"Yes, this is the Crab Nebula."
Old Su was delighted when he heard this, and immediately became motivated, and quickly performed the final focusing according to the operation taught by Xu Yun.
Half an hour later.
Lao Su suddenly let out a slight surprise and said:
"Eh? Xiao Wang, isn't it?"
Xu Yun blinked at him:
"Master, what's wrong?"
Lao Su glanced at him, pointed at the picture in the eyepiece and said:
"Why is there no planet in this light group? Is it just shining like a mist?"
In fact, friends who know the Crab Nebula should know it.
At the inner core of the Crab Nebula, there is a pulsar with a diameter of 20 kilometers.
However, due to equipment accuracy issues, Lao Su obviously could not see the internal conditions of the Taipei - even the Hubble Telescope had to be exposed for more than 24 hours.
Therefore, Lao Su could only judge the stars based on the intensity of the luminous objects, and thus came to the conclusion that there were no stars in the entire nebula.
Xu Yun was silent for a moment after hearing this. He did not explain directly, but said to Lao Su:
"Master, have you ever seen fireworks?"
Old Su stroked his beard, nodded and said:
"Of course."
Fireworks appeared during the Sui and Tang Dynasties, and became popular in the Song Dynasty, and are still relatively common today.
For example, Ling Zhen, the "Thunder Thunder" in "Water Margin".
In addition to supervising the production of firearms in the court, he was also responsible for making fireworks. Bianjing would also set off some fireworks on holidays.
Xu Yun paused and asked again:
"May I ask, sir, what does the fireworks usually look like after they fly high into the sky?"
Old Su thought for a moment, put the five fingers of his left hand together and made an exploding gesture:
"First it rises to a certain height and suddenly explodes. The light shines like daylight for an instant, and then turns into ashes and so on!"
As Lao Su was talking, he suddenly realized something.
He suddenly raised his head and stared at Xu Yun:
"Xiao Wang, are you telling me that fifty years ago, the white light seen throughout Bianjing was the scene of the explosion of the guest star?"
Xu Yun nodded heavily and affirmed:
"Not bad."
Lao Su's pupils suddenly shrank.
stars
Exploded?
All we can see now is the afterglow that has not dissipated?
Lao Su's chest rose and fell a few times, then he took a deep breath and asked:
"Xiao Wang, how does that star compare to the earth?"
Xu Yun thought for a while and replied:
"In terms of quality, at least three million times more."
As everyone knows.
Because the sun does not have enough mass, it cannot become a black hole or a neutron star.
At the end of its stellar life, it will eventually become a red giant and then a white dwarf.
Only stars with more than eight times the mass of the sun will first expand into red supergiants and then explode into supernovae.
Eventually it becomes a black hole or neutron star.
Of course.
There are also cases where white dwarfs eventually turn into neutron stars, which is relatively rare.
Considering that many people do not understand how terrifying neutron stars are, here is a number that is more intuitive than density:
The diameter of a neutron star is generally about ten kilometers, but its rotational speed can reach hundreds of revolutions per second.
That's right.
Every second, not every minute.
That is the moment you blink.
The fastest rotating neutron star discovered so far is named PSRJ1748-2446ad.
Even though it looks like a serial number, it’s actually terrifying:
It has a diameter of 20 kilometers and a rotation speed of 716 times per second.
You can figure out the specific picture by yourself, so I won’t go into details.
all in all.
The protostar of the Crab Nebula can produce a supernova explosion, which means that its mass is at least 8 times that of the sun.
The mass of the sun is 330,000 times that of the earth. Therefore, it is conservatively estimated that the mass of the protostar of the Crab Nebula is more than three million times that of the earth.
Gulu——
Hearing this number, Wang Yue on the side couldn't help but swallowed hard.
As a general who has fought on the Western Front for a long time, he has been exposed to the number "ten thousand" quite a lot.
For example, how many thousands of soldiers, how many thousands of catties of grain and grass, how many thousands of copper coins, etc.
A star with a mass three million times that of the Earth
Three million times
According to Xu Yun.
The area of Bianjing only accounts for one-fifth of the size of the Song Dynasty (the Song Dynasty had a small territory), and the Song Dynasty only had one-twentieth of the continent where it was located
Oh my god.
Wang Yue suddenly found that his brain seemed to be a little insufficient.
In fact, it’s not just Wang Yue.
When everyone present heard this number, their brains almost all shut down for a while.
After coming back to his senses.
Everyone made a unanimous move at the same time:
He looked up at the galaxy.
More than a week ago.
Xu Yun deduced the mass of the earth through the Cavendish torsion scale experiment with the assistance of Lao Jia and others:
That's about six times ten to the 24th power.
And three million times this number.
Looking at the vast world, Lao Su suddenly felt an unprecedented sense of fear in his heart:
Under this galaxy, human beings are really too small
Right now.
Zhang Shuye, who had never spoken, couldn't help it anymore. He bowed his hand to Xu Yun:
"Master Wang, if it is what you said, are there other planets with life in the endless starry sky where the earth is located?"
Xu Yun was silent for a moment and shook his head in confusion:
"Sorry, ordinary people don't know about this."
Different from those who pretended to be stupid before, Xu Yun told the truth this time.
Extraterrestrial life.
This is a quite controversial topic in the 21st century.
Some of them are philosophical and some are scientific.
Just like Lao Su has difficulty truly understanding the concept of 3.3 million times the mass of the earth.
Are the human beings in later generations just like Lao Su at another stage?
But Xu Yun is a person.
Have a positive attitude towards extraterrestrial life.
That is to say, the earth is not lonely, but humans may not be in contact with it yet.
Even if he puts aside his rebirth and mysterious aura, he still won't change his opinion.
After all, the universe is so vast.
There are approximately hundreds of billions of galaxies observed in the known universe, and the Milky Way is just an extremely ordinary galaxy.
In the Milky Way, there are hundreds of billions of stars.
The sun is just an extremely ordinary star.
There are 3000 trillion stars in the entire universe. Who can guarantee that there is no other life or even civilization outside the earth? (doi.org/10.1038%2Fnature0957, data from "nature")
all in all.
Today's observation had a huge psychological and conceptual impact on everyone present, so the atmosphere was a bit dull for a time.
And just when Lao Su was about to relax the atmosphere.
Xiao Li on the side suddenly let out a sigh, pointed in the direction of Beidou, and said in surprise:
"Look there, there's a star!"
Hearing what Xiao Li said.
Everyone present immediately turned their heads and looked north.
really.
I saw a long tail slowly flying south in the corner of the sky.
That's right.
Xingbo refers to a comet.
This is a common name for comets in ancient China, in addition to Pengxing, Changxing, etc.
For the first time, it comes from the record of Lu Wengong’s fourteenth year in "Spring and Autumn":
"In the seventh month of autumn, there are stars entering the Beidou."
However, the name Xingbo seems to be quite elegant, but in ancient China, the meaning of comets was not very good.
Most people call it a broom star and a disaster star, believing that it will bring disaster.
Even a relatively rational person like Lao Su couldn't help but frown when he saw the comet.
But what he didn't notice was.
Among a group of people with frowning faces, solemn expressions and even vague fear.
Xu Yun was slightly relieved when he faced the comet.
Good guy.
Finally waiting for you.
That's right.
This comet is one of Xu Yun's core goals this time!
Its number is 109P/Swift-Tuttle, which returns once every 130 years on average. It is not a particularly famous comet.
The reason why Xu Yun remembered it was not by deriving the date, but by relying on memory:
He is a native of Huqing, Fujian Province. There is a celebrity in his hometown called Cai Boqi, who is also one of the rare historical figures in his hometown.
Xu Yun often played in front of Cai Boyi's stone tablet when he was a child, so he remembered clearly that Cai Boyi's death was on August 4th, 1100 AD.
And according to the epitaph records.
A comet passed by the night before Cai Boyi's death, which was later combined with the cause of Cai Boyi's death.
When he later attended HKUST, Xu Yun made a special trip to check information about this comet and determined its origin.
The two impressions reinforce each other and cannot be forgotten even if they want to.
But if you care, you still care.
109P/Swift-Tuttle is a not-so-famous comet, and it is difficult to observe the structure of the comet's nucleus and coma through telescopes.
In addition, it was fast and did not have much time to adjust the telescope base, so Xu Yun gave up the idea of observing it.
He just stood on the high platform on the mountainside with everyone, watching the comet go away from a distance.
A quarter of an hour later.
The comet disappeared to the south.
Xu Yun slowly turned around and looked at the Song Dynasty Kyoto not far away.
Looking at the brightly lit Bianjing City, the corner of his mouth gradually raised an arc:
Tonight, Xiao Zhao and others went out to Beijing to watch the stars. Presumably an artist is also paying attention to this place.
That is to say.
He should have seen the comet streaking across the sky with his own eyes.
"The next step is up to you, don't let me down."
"Rye Erguotou." (End of Chapter)