It refers to a violent explosion that some stars experience when they are near the end of their evolution.
Such explosions are extremely bright, and the bursts of electromagnetic radiation produced during the process can often illuminate the entire galaxy in which they are located.
It can last for several weeks and then gradually fade away and become invisible over several months.
During this period.
The energy radiated by a supernova is even 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.
After gamma rays come into contact with the atmosphere, they trigger a special chemical reaction:
They convert nitrogen molecules into nitrogen oxide.
This consumes 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 whole process may have only lasted ten seconds, but it destroyed half of the earth's ozone layer.
Eventually, 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. (doi/10.1099/ijs.0.02503-0)
Incidentally.
Currently, Betelgeuse is being discussed a lot 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.
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, there is a high probability that this star has exploded.
Infer based on distance.
As long as you live another 1500-2000 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 most:
For example, the earliest supernova record was SN185, which was 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 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.
That is, 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 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 Shanghai can buy a planetarium ticket for 60, which is absolutely worth it)
However, compared to the first time he observed the moon, Xu Yun did not do it himself this time.
Instead, he let Lao Su try it out on his own.
Again.
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.
"Yeah, yeah, turn the finder 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 model of 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:
"Bisu, one of the twenty-eight places, the fifth place of the White Tiger of the West.
This star's position is marked in the star chart I wrote."
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 the "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 also a more intuitive illustration - have you seen a fork for moistening soil?
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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 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 located 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 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 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 Crab Nebula."
When Lao Su heard this, he 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 right?"
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.
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 Taipei - even the Hubble Telescope had to expose it for more than 24 hours.
Therefore, Lao Su could only judge the stars based on the intensity of the luminous objects, and thus concluded 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:
"Sir, have you ever seen fireworks?"
Old Su stroked his beard, nodded and said:
"Of course."
Fireworks appeared during the Sui and Tang Dynasties, became popular in the Song Dynasty, and are relatively common now.
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 it 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 throughout 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 we all know.
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 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.
That's 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 cycles 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 3 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.
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...
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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 regaining consciousness.
Everyone made a unanimous move at the same time:
He looked up at the stars.
More than a week ago.
Xu Yun deduced the mass of the earth through the Cavendish torsion balance experiment with the assistance of Lao Jia and others:
It's about 6 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...
At this moment.
Zhang Shuye, who had never spoken, couldn't help it anymore, and he bowed his hand to Xu Yun:
"Master Wang, if it is as you said, are there other planets with life in the endless starry sky where the earth is?"
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 of later generations just like Lao Su at another stage?
But Xu Yun personally...
He has 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/10.1038/nature0957, 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 lighten 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!"
I heard what Xiao Li said.
Everyone present immediately turned their heads and looked north.
really.
I saw a long tail flying slowly southward in the corner of the sky.
That's right.
Stars refer to comets.
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, 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.
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 famous person in his hometown named 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 the University of Science and Technology of China, Xu Yun 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.
But I still care if I 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 a 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..."