Astronomy enthusiasts should know this.
The so-called supernova explosion.
It refers to a violent explosion that some stars will 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.
When gamma rays come into contact with the atmosphere, they trigger a special chemical reaction:
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.
In 2005, the results of a joint study by NASA and the University of Kansas showed.
This mass extinction event was probably caused by a gamma-ray burst released by a supernova.
According to model reduction, the entire process may have only lasted ten seconds, but it destroyed half of the earth's ozone layer.
In the end, ultraviolet rays from the sun hit the earth, causing the death of a large number of organisms on the surface, thus causing a mass extinction of organisms. (/10.1099/ijs.0.02503-0)
Incidentally.
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...basic physical rules.
In addition to Betelgeuse, another planet 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, there is a high probability 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 many of the most:
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 galactic 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 supernovae 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 spectacle 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 arcminutes long and 4 arcminutes wide, making it 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 Shanghai can buy a planetarium ticket for 60, which is absolutely worth it)
However, compared to the first time when he observed the moon, Xu Yun did not do it himself this time, but asked Lao Su to try it himself.
Again.
It is better to teach a man to fish than to teach him to fish.
"Yeah, yeah, turn the finderscope first, wait, it's over."
"The cross hairs are closer..."
Seeing 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 pacesetter in learning.
after awhile.
Seeing that Lao Su was almost ready, Xu Yun asked:
"Sir, can you recognize the direction of Bisu?"
Lao Su nodded without much hesitation this time and said:
"Bissu, one of the twenty-eight constellations, the fifth constellation of the White Tiger of the West.
This star position is marked in the star chart written by me. "
Bisu, 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. Ancient people believed that its appearance was very similar to "Bi", a long-handled tool used to capture small animals.
Therefore, it was passed down from generation to generation and was named Bisu.
Of course.
There is 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 for 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 most familiar person in the contemporary era with star maps, Lao Su quickly located the area where Bisu was located after receiving Xu Yun's guidance.
Xu Yunjian continued:
"Sir, if I remember correctly, the supernova is northeast of Biju..."
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 this old 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!".
Abominable tentacle monster.jpg.
that's all.
after awhile.
Lao Su's expression suddenly shook, and he waved towards Xu Yun with his left hand:
"Xiao Wang, come and see, this star...or is this object 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 makeup remover nebula."
Lao 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 light 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 glowing like a mist?"
In fact, friends who know the Crab Nebula should know it.
In 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 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 usually happens after fireworks fly high into the sky?"
Lao 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...wait a minute!"
As Lao Su was talking, he suddenly realized something.
He suddenly raised his head and stared at Xu Yun:
"Xiao Wang, you mean... Fifty years ago, I... no, the white light seen in the entire Bianjing was the scene of the explosion of the guest star?"
Xu Yun nodded heavily and affirmed:
"good."
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...it's probably more than three million times...at least."
As everyone knows.
Due to insufficient mass, the sun cannot become a black hole or 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 a white dwarf star eventually turns into a neutron star, 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, just 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 as hell:
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 '10,000' 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.
And 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 realized that his brain seemed to be a bit exhausted.
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 that 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, and he bowed his hand to Xu Yun:
"Master Wang, if it is what you said, is there life on other planets 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?
However, Xu Yun is personally optimistic about extraterrestrial life - even if rebirth and mysterious aura are put aside, it is just that humans may not be exposed to it yet.
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, and 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? (/10.1038%2fnature0957, data of "nature")
Today's observation has had a huge psychological and conceptual impact on everyone present...
And just when the atmosphere was getting a little dull.
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.
The first time it comes from the record of Duke Wen of Lu in the 14th year of the Spring and Autumn Annals:
"In the seventh month of autumn, there are stars entering the Big Dipper."
However, in ancient China, the meaning of comets was not very good. Most people called them broom stars and disaster stars, believing that they would 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!
It is numbered 109p/swift-tuttle and returns once every 130 years on average. It is not a particularly famous comet.
Xu Yun remembered it 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 record, a comet passed by the night before Cai Boyi's death, which was later combined with the cause of Cai Boyi's death.
After Xu Yun entered HKUST, he made a special trip to check the information about this comet and determined its origin.
The two impressions reinforce each other and cannot be forgotten even if you want to.
109p/swift-tuttle As a comet that is not particularly famous, it is difficult to observe the structure of the comet nucleus and coma through a telescope. In addition, its speed is relatively fast, so Xu Yun gave up the idea of observing it.
He followed the others and stood on a high platform on the mountainside, watching the comet go away from a distance.
Xu Yun then turned around and looked at the brightly lit Bianjing city.
The corner of his mouth raised a slight 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."
...........
Note:
For the sake of coding all night long, give me a monthly pass, woo woo woo.
