When you stare into the abyss

The abyss is staring at you

April 2019

The first photo of a black hole was released

For the first time, man gazed at the abyss of the universe

(The first photo of a black hole taken by humans, from @ EHT Collaboration, labeled @ Xiaohei/Star Research Institute)

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At this time

People's doubts about the existence of black holes

More than 100 years have passed

For black holes

This is just a moment

But for humans

It's a long journey that constantly subverts the imagination

And it is this thought storm that has lasted for more than 100 years

So that we can write this article

Show you the darkest abyss in the universe

(Black hole artist's imagination, photo source: @ wikimedia commons)

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that

What on earth is a black hole?

Why is it so powerful?

So that all matter, energy and even light

Cannot escape its deadly attraction

(NGC 1097 bar spiral galaxy in the constellation Fornix, where there is a massive black hole in the center of the galaxy, photographer @ Yan Zhipeng)

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To answer these questions

Let's start with an astronomical mystery

01 Suspect

1964

Scientists in the direction of Cygnus in the Milky Way

Accidentally found a blue star

Its mass and temperature are far higher than those of ordinary stars

There are also two questions that are puzzling

(Betelgeuse and its surrounding stars. Betelgeuse is also a celestial body whose brightness and mass are far more than ordinary stars. This picture is just for illustration. It's not the blue star in the constellation Cygnus. Photographer @ Ou Mingzhi)

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One doubtful point

As a single star in the Milky Way

While it revolves around the center of the Milky Way

And spin around in another elliptical orbit

(The position of the sun in the Milky Way, it only revolves around the center of the Milky Way, without any other revolution movement, photo source: @ NASA/JPL Caltech/ESO/R. Hurt)

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Doubt 2

Near this blue star

Scientists have detected intense high-energy radiation

But it cannot produce such high energy

Do you?

Is there another object around this star?

It is its existence that changes the motion orbit of the star

And produce strong radiation?

however

If such celestial bodies really exist

Why can't people see it?

In order to explain these doubts

People remembered an ancient prophecy

02 Prediction

As early as the 18th century

There are scientists who predict

There is a special celestial body in the sky

Its gravity is very strong

So that even light cannot escape from it

So we won't be able to see this object

This dark celestial body is Dark Star

(Please view the horizontal screen, the black hole artist's imagination picture, the black hole is located at the center of the brightest area in the picture, the picture source is @ ESO/M. Kornmesser)

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But then

All known physical theories

Can't deal with this "dark star"

Make a reasonable explanation

Until 1915

Einstein completes general relativity

Vague predictions have a real theoretical basis

Soon

Karl Schwarz, German soldier and astronomer

On the battlefield of the first world war

The radius formula of "dark star" is calculated

Described the "influence" range of "Dark Star" for the first time

This formula is called Schwarzschild radius

And the name "dark star" here will be

A louder name replaces

black hole

(Karl Schwarzenegger, Einstein's general theory of relativity predicted the existence of black holes, and Schwarzenegger gave the first solution of the theoretical equation, so there is a type of black hole named after him, photo source: @ wikimedia commons)

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Schwarzschild radius indicates

The greater the mass of the black hole

The greater the scope of its "influence"

If we compress the earth into a black hole

Then its Schwarzschild radius is only about 9 mm

amount to A dime Size of

(Hubble Telescope and Earth, photo source @ Visual China)

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Take Schwarzschild radius as the boundary

There are two worlds inside and outside the black hole

Everything that happens inside a black hole

Can't see from the outside

Therefore, this boundary is also called Event horizon

(NGC 3201 black hole artist's imagination picture, black holes have an impact on nearby space-time, photo source: @ ESO/L. Cal ç ada)

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When matter passes through the event horizon and enters the black hole

Will fall irresistibly toward the center

There is infinite density singularity

There will be no "return road" for matter

It sounds so magical

But does such a black hole really exist?

03 Clues

Just as the research on black holes is booming

Affected by the outbreak of World War II

Many physicists have devoted themselves to the study of the atomic bomb

Including "the father of the atomic bomb" Oppenheimer

In the late 1930's, from the perspective of star evolution

Predicted the existence of black holes

In 1942

Oppenheimer was appointed

Chief scientist of the Manhattan Project

Started to focus on the development of the atomic bomb

That's it.

The topic of black holes is gradually forgotten
Until the discovery of another theoretical celestial body

Rekindled people's enthusiasm for studying black holes

(Oppenheimer [first from left] is showing the photos of the atomic bomb explosion to the people around him. The photo source is @ Visual China)

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1967

Scientists repeatedly receive

A strange signal in the universe

It will visit the earth on time every 1.337 seconds

At first scientists thought it was a message from an alien civilization

Later confirmed

This signal comes from a fast rotating neutron star

A celestial body composed almost entirely of neutrons

It radiates electromagnetic waves from the celestial poles

Keep sweeping through the deep space

Like a cosmic beacon

To guide travelers in the vast universe

(The high-speed rotating neutron star is a sign. Shortly after the discovery of the neutron star, John Wheeler first used the term black hole. The picture comes from @ new film field, marked @ Xiaohei/Star Research Institute)

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And neutron stars are like black holes

Are the ultimate fate of stars

Like creatures on earth

Stars in the universe also have "life and death"

In the star survival stage

The burning of its own fuel makes the star "expand" outward

So as to resist the mutual attraction of substances

The inward "contraction" brought by

When the two forces reach balance

And the stars will remain stable

(The burning sun has been undergoing nuclear fusion reaction inside the sun, which has made the sun stable for hundreds of millions of years. Since the mass of stars and other celestial bodies in the universe is usually large, the mass of the sun is generally used as the basic unit when measuring their weight, photographer @ Wang Jiaqi)

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But the star's fuel will be used up one day

At this time, the power generated by burning disappears

The star collapses rapidly inward under the action of gravity

Forming a very dense Compact celestial body

Other excess material is thrown away

The stars die

And what dense objects will eventually form

Depends on the mass of the star

Stars below 8 times the mass of the sun collapse into

Small size with high surface temperature White dwarf

Its maximum mass is only 1.44 times the solar mass

This is the final outcome of our sun

(Sirius has star A and star B. Sirius B was identified as a white dwarf in 1915, but its brightness in the sky is far less than that of star A, so we can only see the light of star A on the ground. In the ancient astrology of China, Sirius "is the main threat of aggression". Su Shi wrote in "Jiangchengzi · Hunting in Michigan" that "he will draw a bow like a full moon, look northwest, shoot Sirius" , Sirius is compared to Xixia at the border of Northern Song Dynasty, photographer @ Wang Jin)

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Stars with 8~30 times the mass of the sun will collapse into

neutron star

(Vela supernova remnant, the remnant left after the star collapsed into a neutron star, the material energy in the remnant area is high, showing bright colors in the visible and X-ray bands, photographer @ if you have hands)

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Middle sub star mass exceeds 3.2 times solar mass Hour

Will further collapse

formation black hole

(Please view the artist's image of the supermassive black hole on the horizontal screen, photo source: @ NASA/JPL Caltech)

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before

The compact objects formed after the death of these stars

Only white dwarfs are confirmed by observation

With the discovery of neutron stars

People have reason to believe

black hole

Maybe there is frankness

The shining cosmic lighthouse

It seems to be illuminating the direction of searching for the truth of black holes

04 Truth

1975

Hawking, a famous physicist

Just bet Kip Thorne, a physicist

Hawking thinks that the weird blue star

The unknown objects nearby are not black holes

Kip's view is the opposite

In the subsequent years of observation

More and more evidence shows that

The unknown object has a mass of 8.7 times that of the sun

Exceeded the limit of 3.2 times the solar mass of neutron star

So it's a black hole

(Please watch it horizontally. The artist can imagine the Swan X-1 black hole and the nearby blue stars. Cygnus X-1 is the first black hole discovered in human history. Its name means that it is the first X-ray source found in Cygnus. X-ray is a kind of high-energy electromagnetic wave. Photo source: @ ESA/Hubble)

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One night in June 1990

Hawking broke into Kip's office with the help of his assistant

Sign a bet and admit defeat

And humorously put thumbprint on the bet

Actually, for Hawking, who studies black holes

This is the end he expected

(Hawking and Kipshorn [first from left], the result of scientists're measurement of the black hole X-1 in Cygnus in 2021 is 21.2 times the solar mass, photo source @ Visual China)

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That's it.

Man discovered the first black hole

Then all the doubts before

Then they have a reasonable explanation

The existence of a black hole bends the surrounding space-time

The blue star rotates around the black hole along a curved orbit

This is a black hole Gravitational action Embodiment of

(The artist imagines that the existence of the black hole in the center of the Milky Way Galaxy causes the surrounding stars to make elliptical movements around it. The blue circle marked is the location of the black hole, photo source: @ ESO/M. Parsa/L. Cal ç ada)

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Understand one of the doubts

Another doubtful point will be solved

The powerful gravity of black holes

Attract the matter on the blue star

Spin them into a black hole

Accumulate to form a disc structure around

be called Accretion disk

(The visual simulation of the black hole accretion disk shows that the accretion disk seen from different angles will have different changes due to the strong gravity of the black hole, and the light of the accretion disk behind the black hole will bend when propagating forward. Image source: @ NASA's Goddard Space Flight Center/Jeremy Schnittman, labeled @ Xiaohei/Star Research Institute)

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The substances in the disc rub against each other

Generate a high temperature of millions of degrees Celsius

So as to produce high-energy radiation

(Artist's Imagination of Black Hole Accretion Star, photo source: @ NASA's Goddard Space Flight Center/Chris Smith (USRA/GESTAR), labeled @ Xiaohei/Star Research Institute)

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in addition

Not all the accreted matter falls into the black hole

Affected by black hole magnetic field and other factors

A part of the material will converge into a narrow material flow

Jet out

Like a sword stabbing into the deep sky

be called Jet

These ejected materials are scattered in space

New celestial bodies will be bred in the future

(The ultra long jet structure in the galaxy Hercules A captured by the Hubble Space Telescope, photo source: @ NASA/ESA)

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Compared with the black hole itself

Its accretion disk and jet are bright and visible

This has become a powerful means for astronomers to find black holes

(Schematic diagram of black hole structure, photo source @ ESO, ESA/Hubble, M. Kornmesser/N. Bartmann， Mark @ Xiaohei/Star Research Institute)

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More Than This

The fatal attraction of the black hole has left more clues

When light passes around the black hole

Will inevitably spread along the curved space-time

Seen from the surface phenomenon

Light doesn't go straight

It's turning

(The existence of a black hole changes the trajectory of light passing by, mapping @ Xiaohei/Star Research Institute)

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When there is another compact object near the black hole

This gravitational action will make

Two celestial bodies revolve around each other

And finally merge into a black hole with greater mass

(Schematic diagram of double black holes circling motion simulation, photo source @ NASA, label @ Xiaohei/Star Research Institute)

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In this process

Disturbance occurred in the curved space-time near these two celestial bodies

And radiate outward in the form of waves

This is the ripple of time and space
Gravitational wave

(Two compact celestial bodies rotating around each other radiate gravitational waves outward, cartography @ Xiaohei/Star Research Institute)

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In 2015, human successfully detected for the first time

Gravitational waves generated by the merger of two black holes

It crosses 1.3 billion light years to reach the earth

According to it, scientists calculated the mass of the double black holes

If astronomy before that

Humans use "eyes" to see

And the successful detection of gravitational waves

Means that humans can use "ears"

Listen to the whispers from the universe

(Comparison of the mass of black holes in gravitational wave merging events measured by the American Laser Interferometric Gravitational Wave Observatory, the merging of black holes with other celestial bodies is one of the ways of black hole mass growth, cartography @ black smashing/star research institute)

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Through these methods

Human beings have explored more and more black holes

But in the eyes of physicists, it is incredibly simple

Only three physical quantities are enough to cover all

The first indicator is "multiple"

that is quality

The second indicator is "Rotation"

Usually used angular momentum express

The third indicator is "with or without electricity"

I.e charge

According to mass, black holes can be divided into three categories

Black holes less than 100 times the mass of the sun

this is Stellar black hole

Most stars in the universe end up with black holes like this

Black holes with a mass of more than 1 million times the sun

be called Supermassive black hole

Black holes of this level generally exist in the center of galaxies

Is a key figure in the evolution of galaxies

Between stellar black holes and supermassive black holes

yes Medium mass black hole

Compared with the first two black holes

Due to the small number of observations

We don't know enough about such black holes

(Comparison between the mass of compact celestial bodies and that of the sun. The sun is not a compact celestial body, and the picture is just a comparison. The photo is from @ NASA/CXC/Visual China/Wang Jiaqi, cartography @ Heibang/Star Research Institute)

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In addition to classification by quality

According to angular momentum and charge

Black holes can also be divided into four types

(The following figure shows the classification of black holes according to rotation and charge. The image source is @ Visual China, and the label is @ Heibang/Star Research Institute)

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Although we have explored so many mysteries of black holes

But this is only through

Accretion disk, jet

Gravitational action, gravitational wave

These indirect methods find it

Like we can't see the wind

But it can pass through the sand blown by the wind

The indirect judgment of the existence of wind is the same

(Please watch on the horizontal screen. Yadan landform is a typical wind erosion landform, which cannot be formed without the role of wind. Photographer @ Sun Qi)

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Human curiosity drives scientists to want

"Seeing is believing"

What does a black hole look like?

Can the black hole show its "real body" directly?

05 Appear

Take pictures of black holes

Is the answer given by physicists

But it needs

An unprecedented super telescope

Aimed at observing supermassive black holes

Event horizon telescope

(Event Horizon Telescope, short for EHT ）

emerge as the times require

(Imagination of black hole artists "eating", bright accretion disks and jets prove its existence, photo source: @ Aurore Simonnet and NASA's Goddard Space Flight Center)

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first

We need to select the subject

In order to be able to Visible and photographed clearly black hole

Large mass and close to the earth are necessary conditions

M87 galaxy near the Milky Way

There is such a supermassive black hole

Its mass is 6.5 billion times that of the sun

(M87 galaxy, the highlight in the picture, picture source @ ESO)

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Although this black hole is so huge

But it is still 55 million light years away from the earth

Look at it from the earth

It is equivalent to seeing the footprints on the surface of the moon

This is a great test of telescope resolution

(Observation of footprints on the moon from the earth, cartography @ Zheng Yi/Planetary Research Institute)

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The larger the aperture of the telescope

The higher its resolution

"China's Celestial Eye" in Guizhou

It is the largest single aperture radio telescope in the world

Its caliber reaches 500 meters

But it still cannot meet the requirements of scientists

Want to take pictures of black holes

The telescope aperture should reach the "earth level"

(Located in the "China Sky Eye" among mountains, photographer @ Cool Bird Wei Jian)

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Single telescope doesn't work

Then try to use multiple telescopes

Scientists use special methods

Combine radio telescopes distributed around the world

Equivalent to a virtual telescope with larger aperture

This is the very long baseline interferometry technology

（Very Long Baseline Interferometry）

abbreviation VLBI

The distance between telescopes is called baseline

The diameter of the virtual telescope is equivalent to

The farthest baseline length

The longer the baseline

The higher the resolution of the virtual telescope

(Please view horizontally. The circular array solar radio imaging telescope in Daocheng, Sichuan, also known as the "Thousand Eyes Sky Pearl", 313 antennas are equivalent to a virtual telescope, photographer @ Lan Yanbin)

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Participated in the first black hole shooting 8 sets Telescopes are distributed in

Mexico, Spain, Chile, Antarctica

Hawaii and Arizona

They form a virtual telescope with an aperture equivalent to the diameter of the earth

(The distribution of EHT telescope array in 2017, the English name marked in the figure below is the abbreviation of the English name of the telescope, mapping @ Zheng Yi/Planet Research Institute)

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Got the aperture of the telescope

But it does not mean that the observation can be started immediately

Because we need to combine them perfectly

Must be observed at the same time

Taking weather, observation task arrangement and other factors into consideration

8 radio telescopes participating in the shooting

The observation time in 2017 is only 10 days

(Please view horizontally. The James Clark Maxwell Telescope (JCMT) and the Submillimeter Wave Array (SMA) located on the 4000 meter mountain in Hawaii, the United States, have a good observation effect in the high altitude environment, and must be carried out in sunny weather, because the moisture in the atmosphere will affect the observation, photographer @ Yu Le)

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Although the observation time is short

But the data obtained is very rich

The total amount of observation data generated has reached 3500TB

It takes more than 300 years to watch the movie

But just processing these data

It costs 2 years Time of

April 10, 2019

The first photo of a black hole was released

Is jokingly called by scientists Donuts

The bright outer circle is the accretion disk around the black hole

The shadow in the middle is the region where the black hole is located

(The first black hole photo, from @ EHT Collaboration, labeled @ Xiaohei/Star Research Institute)

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M87 black hole also has a jet about 5000 light-years long

But this time, only the black hole and its accretion disk were photographed

"Family member" is not complete

(The jet structure of M87 black hole, that is, the strip shape in the figure, picture source: @ wikimedia commons)

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So in 2018

International team led by Chinese scientists

Use the same technical means

Photograph M87 black hole again at the new observation band

The telescope's field of view is larger in the new wave band

More black hole structures can be seen

More Than This

The number of telescopes has also increased from 8 last time to 16 sets

Greatly improves the imaging quality of the virtual telescope

(The geographical location of the telescopes that took part in shooting black holes in 2018 is as follows, mapping @ Zheng Yi/Planet Research Institute)

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April 2023

Scientists released the "panorama" of M87 black hole

It is the first time to image a black hole and its surrounding structure in a picture

(The "panorama" of M87 black hole shows that the jet structure is represented by three parts, with the shape similar to the "trident". The picture is from @ R. - S. Lu (SHAO)/E. Ros (MPIfR)/S. Dagnello (NRAO/AUI/NSF), marked @ Xiaohei/Star Research Institute)

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After 5 months

Chinese scientists have proved that

This black hole that humans first "see"

Is on rotate Of

Before that

Whether the black hole is rotating

No direct observational evidence

(The precession of M87 black hole jet shows that the spin axis of the spin object is still rotating around another central axis, which is known as precession. Source of material @ Cui Yuzhu, Intouchable Lab@Openverse , marked @ Xiaohei/Star Research Institute)

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Except for the distant M87 black hole

The galactic center where we live

There is also a supermassive black hole

Scientists also took pictures of it

(The photo of the black hole in the Milky Way and the central region of the Milky Way released in 2022 also looks like a doughnut. The photo source is @ NASA/CXC/HST/EHT Collaboration, with the label @ Xiaohei/Star Research Institute)

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Imaging black holes is a breakthrough in astronomy

But this is only the first step to explore black holes

Scientists will try more in the future

For example, shooting black holes at different wavelengths Color Photo

Even with the time dimension "Black Hole Movie"

Maybe by then

Accompanied by more comprehensive observation and understanding

Black holes will no longer be mysterious

06 Ending

black hole

With its deadly gravity

Not only attract everything

It also attracts people to explore constantly

Its existence

Once beyond human imagination

Even Einstein once doubted

But it turned out to be real

The universe is so magical

It's not too late to see

The exploration of black holes also tells us

Only let the mind keep soaring

So that human beings can surpass the fixed concept

Enter a new world

therefore

In the following exploration journey

Please keep thinking

But more than 100 years

(The sky above is full of infinite unknown and possibility, photographer @ Windsky)

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This article creation team

• By: Galaxy
• Edit: Li Heili
• Picture: Zhang Zhaohai
• Map: Zheng Yi
• Design: Xiaohei&Heizao
• Reviewed by: Wang Kun&Song Nan
• Cover Source: NASA/JPL-Caltech

Audit experts

• Feng Haiyuan, Doctor of Theoretical Physics, Southern University of Science and Technology
• Note: The event horizon and singularity of black hole discussed in this paper are based on the background of Schwarzschild black hole.

[References]

• [1] Zhao Zheng, Liu Wenbiao Fundamentals of General Relativity [M] Beijing: Tsinghua University Press, 2010
• [2] Yuan Yefei, Tang Zeyuan Imaging observation of supermassive black hole at the center of neighboring galaxy M87 by the event horizon telescope [J] Science Bulletin, 2019, 64 (20): 5
• [3] Zhao Xueshan, Feng Ye, Gou Lijun Interpret the latest parameter measurement results of Cygnus X-1 [J] Nature, 2021, 43 (3): 209-216
• [4] Alan Lightman Accidental universe [M] Wu Fengfeng Shanghai: Wenhui Publishing House, 2023
• [5] Neil Douglas Tyson (US), Donald Goldsmith (US) 14 billion year history of cosmic evolution [M] Sunlight Beijing: Beijing United Publishing Company, 2019
• [6] Hong Xiaoyu, Zhang Xiuzhong, Zheng Weimin, etc Research progress of VLBI technology and its application in China's lunar exploration project [J]. Journal of Deep Space Exploration (Chinese and English), 2020,7 (04): 321-331
• [7] Lu, RS., Asada, K., Krichbaum, T.P. et al. A ring-like accretion structure in M87 connecting its black hole and jet. Nature 616, 686–690 (2023).
• [8] Edgar Castillo-Domínguez. First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole[J]. The Astrophysical Journal Letters, 2019, 875(1).
• [9] Edgar Castillo-Domínguez. First M87 Event Horizon Telescope Results. II. Array and Instrumentation. 2019[2023-10-07].
• [10] MILLER-JONES J C A, BAHRAMIAN A, OROSZ J A, et al. Cygnus X-1 contains a 21-solar mass black hole – Implications for massive star winds [J]. Science, 2021, 371: 1046-1049. DOI: 10.1126/science. abb3363.

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