The Cygnus v404 black hole (V404cygni) woke up in June of this year. Pen "Fun" Pavilion www.biquge.info

She has slept for 26 years since her last outbreak, and the post-90s generation in this world has not seen her last outbreak.

No one knows the geometry of her face, but we can read her message from a distant universe 7,800 light-years away - written in high-energy gamma rays and X-rays!

The Swift satellite in the United States was the first to receive the news of the awakening of the black hole in the constellation V404 in the constellation Cygnus and notified the citizens on the dim blue dot.

A super black hole it woke up......

The image on the left is a map of the position of Cygnus V404 in the sky; The picture on the right shows a promotional image of the U.S. Swift satellite

A super black hole it woke up......

This graph shows the change in brightness of Cygnus V404. In addition to this, there are also sources of brightness variation, which are continuously bright for CYGX-1 and CYGX-3

We should be grateful for the prosperity of science fiction literature and science fiction films, which have allowed many ordinary people to recognize and even "witness" black holes. Now, perhaps even a middle school student knows that the gravitational pull of a black hole is so great that it tears everything apart, and even light cannot escape.

Albert Einstein proposed the great general theory of relativity 100 years ago, arguing that when all mass is concentrated in a very small singular point (qi), a huge gravitational force is generated within a certain range, which is the reason why black holes devour everything.

The "Eyes" that Look into the Depths of the Universe

Seeing this, you may ask me, since even light cannot escape the palm of a black hole, how can we observe the black hole of "black hole"?

The human eye can only see a very narrow spectrum of electromagnetic waves, and if you are lucky enough to get a pair of glasses that can see X-rays, you will see a completely different picture of the universe: our sun will be much darker than it is now, and there will be no more stars in the night sky, but only a few bright spots scattered among them - because there are very few point source objects that can produce such high-energy radiation - only neutron stars, black holes, and a few white dwarfs.

So, put on these magic glasses and you can see the Cygnus V404 black hole awaken, which is the brightest point in the sky, three times brighter than the brightest known X-ray object, Scorpio X-1 (SCOX-1).

For all mankind, telescopes are such a magic pair of glasses: optical telescopes help us see fainter celestial bodies, and telescopes in other wavelength bands help us understand everything in the universe beyond optics.

Of course, scientists can't directly see the "black hole monster" with its mouth wide open and never get enough to eat, and all humans can do is to indirectly detect black holes.

The observation of black holes that we will talk about next is not the "naked eye observation" that earthlings take for granted, but the observation through a telescope that can see various rays.

A super black hole it woke up......

The secret to detecting black holes

There are two types of black holes in the universe that we are able to identify:

One is black holes of the magnitude of stars. It has a mass larger than the Sun, about 10 solar masses, and this type of black hole, like any other star, can be found in all corners of the galaxy. In the case of our galaxy, it is estimated that there are more than 10 million of them.

Another type of black hole is called "supermassive black hole". Such black holes often have the mass of at least a few million suns (in 2014, Chinese astronomers discovered a black hole that weighs as much as 1 billion suns!). ), which usually exist alone in the center of galaxies.

Although the mass of these two types of black holes is very different, they will produce similar astronomical observation phenomena, which can hide the secret of human observation and detection of black holes!

The first is the bright and beautiful accretion disk around the black hole.

By accretion of nearby gas, a disk of gas (i.e., accretion disk) is formed around the black hole, and the gases in the disk rotate around the black hole, rubbing against each other to produce a great amount of energy, which is released by the radiation of light, which is seen by the telescope on the ball or the space telescope.

However, due to the limitations of the telescope's ability to observe, the specifics of this spectacular spectacle can only be seen in movies, as shown in the movie "Interstellar". It is the result of an animation company visualizing a black hole based on a large amount of computational data under the guidance of scientists.

The second phenomenon is jet streams.

Unlike accretion disks, jets have a larger spatial scale and are easier to see with telescopes. In some cases, a black hole that accrectifies gases will quickly eject excess, unentered black holes, which are made up of charged particles and contain magnetic fields, so they produce radiation that allows us to detect its presence.

It is the above two manifestations of black holes that allow humans to know about their existence. For the Cygnus V404 black hole, which has been sleeping for 26 years, it is precisely by accretion that enough gas is accretion from the companion star, and the accretion disk produces an explosion, which produces very strong high-energy radiation and brings a message to earthlings.

The Cygnus V404 black hole woke up for more than ten days this time. In this short but violent burst, the entire accretion disk was destroyed.

Over the next few decades, Cygnus v404 will need to re-accumulate gas from its companion star in preparation for the next eruption.

A super black hole it woke up......

Diagram of black holes accreting gas from companion stars; The locations of jets, accretion disks, and black holes are all marked. Please note that this is a schematic diagram only and the dimensions are not exactly proportional

Weigh the black hole

Therefore, although the black hole is pitch black, it sometimes shows us its existence and great power through some material activities around it.

So, when news of a suspected black hole comes from the depths of the universe, how can astronomers confirm that it is a black hole? You know, neutron stars also have accretion disks and jets.

This requires scientists to measure the "weight" of what is suspected to be a black hole.

First of all, theoretically, if a compact object has a mass greater than 3 solar masses, because there is no known force to support its own weight, it will collapse towards the center to form a black hole of the magnitude of stars, but because the black hole itself does not emit light, we can only see and measure the mass of the black hole when there are companion stars around the black hole.

In fact, there are supposed to be tens of millions of stellar black holes in our galaxy, and we have only confirmed more than 60 so far, because when the black hole and the companion star orbit together, we can use simple laws of physics to measure the mass of the black hole through the orbit of the companion star. This method is similar to using the motion of the moon to measure the mass of the earth and the motion of the earth to measure the mass of the sun.

In 1974, theoretical physicist Stephen Hawking and his good friend Kip Thorne, two of Earth's brightest brains, made a bet on whether humanity's first black hole candidate, Cygnus X-1 (Cygx-1), was a black hole, and they made a bet on the year-old adult magazine Attic.

Later observations measured the mass of the black hole, which was about 15 solar masses, using the motion of the companion star in Cygnus X-1, prompting Hawking to admit defeat and put his handprint on the bet book between the two.

A super black hole it woke up......

Hawking and Thorne's bet contract on the Cygnus X-1 black hole (from the book Black Holes and the Bending of Space-Time - The Ghost of Einstein)

Both of the previously mentioned types of black hole mass can be measured in this way. For example, the massive black hole of the Milky Way galaxy is located in the constellation Sagittarius, and its name is SGRA*, with a mass of about 4 million solar masses.

The Cygnus V404 black hole has returned to calm after a brief eruption, so let's look forward to her awakening again. (To be continued.) )