Space and astronomy

Everything You Need to Know about the Black Holes: One of the Most Mysterious Things in Space

Black holes are among the most enigmatic and complex phenomena in the universe. Have you ever wondered whether these black holes are accurate or just a theory? Can something be so black to the extent of swallowing even light? Let’s explore together with Wesam Web the astonishing secrets of black holes and paint a clearer picture of this mysterious phenomenon in space.

What Are Black Holes?

Everything You Need to Know about the Black Holes: One of the Most Mysterious Things in Space
black hole

According to a simple definition, black holes are points in space with highly high gravity and density from which not even light can escape. This attraction is so strong that it compresses all matter into a tiny space. These enigmatic black points are formed from the remnants of massive stars that underwent gravitational collapse.

Albert Einstein first suggested the possibility of black holes in 1916 with his theory of general relativity. The term “black hole” was coined several years later in 1967 by American astronomer John Wheeler. According to general relativity, a sufficiently compact mass can curve spacetime (the four-dimensional space comprising three dimensions of space and one of time) and create a black hole.

The point of no return for a black hole is the event horizon. Black holes do not reflect any light, but their presence can be inferred from their effects on surrounding materials and objects.

How Are Black Holes Formed?

Black holes are formed through a process known as gravitational collapse. This occurs when a massive star exhausts its nuclear fuel and lacks the energy to balance its gravity.

A star generates energy throughout its life through nuclear fusion, where hydrogen atoms fuse to form helium, releasing immense amounts of energy. This energy creates an outward pressure that counteracts the star’s internal gravitational force, pulling material inward.

As most stars approach the end of their lives, they swell and shed mass, ultimately becoming frozen white dwarfs. However, massive stars with masses ten to twenty times that of the Sun transform into neutron stars or black holes.

In the end, when a massive star burns through all its nuclear fuel, its core becomes unstable and undergoes gravitational collapse, destroying its outer layers. These stars explode in a gigantic blast known as a supernova, leaving behind black holes or neutron stars. Astronomers categorize black holes into three types: stellar black holes, massive black holes, and intermediate-mass black holes.

Stellar Black Holes

Stellar black holes are a specific type of cosmic void formed from the gravitational collapse of massive stars. When a vast star reaches the end of its lifecycle, it undergoes a supernova explosion, expelling its outer layers into space. What remains is the star’s core, which collapses under its gravity, forming a stellar black hole.

The formation of a stellar black hole begins when a star’s core, several times the mass of our Sun, can no longer sustain nuclear fusion. The outward pressure from fusion reactions ceases, and gravity takes over, causing the core to collapse. The collapse is so intense that it creates a singularity—an infinitely dense point—at the center of the black hole.

Surrounding the singularity is the event horizon, which marks the boundary beyond which nothing can escape the gravitational pull of the black hole. The event horizon is a spherical region with a radius proportional to the black hole’s mass. Any matter or radiation that crosses the event horizon is trapped, resulting in the distinctive “blackness” of a black hole.

Stellar black holes can have a wide range of masses, typically ranging from a few times the mass of our Sun to about 20-30 times its mass. These black holes persist and exert their gravitational influence on the surrounding space, yet they do not actively consume material or grow significantly unless they interact with nearby objects.

Stellar black holes are of great interest to astronomers as their presence can be inferred from their effects on their surroundings, such as the gravitational influence on nearby stars or the emission of X-rays from infalling matter. By studying these effects, scientists can learn more about the properties and behaviors of these fascinating entities in our universe.

Massive Black Holes

Massive black holes constitute a category of dark voids with much larger masses than stellar black holes. They reside at the centers of galaxies, including our own Milky Way. The groups of these black holes range from hundreds of thousands to billions of times the mass of our Sun.

The precise formation mechanism of supermassive black holes remains a subject of ongoing research, with several theories proposed. One possibility is that they form through the gradual accumulation of mass over time. This could occur through the merger of smaller black holes or the accretion of dense gas clouds, gradually building up the mass of the black hole. Another hypothesis suggests that massive black holes formed directly from the collapse of enormous gas clouds in the early universe.

Supermassive black holes have a profound impact on their host galaxies. Their immense gravity affects the motion of stars and other celestial bodies. They can also play a crucial role in galaxy formation and evolution. The energy emitted during the growth of a supermassive black hole can influence the surrounding gas and dust, regulate star formation, and shape the overall structure of the galaxy.

One distinctive feature of supermassive black holes is the presence of an accretion disk. When surrounding material, such as gas or stars, falls toward the black hole, it forms a rotating disk around it. Frictional forces and gravity within the disk heat it and emit intense radiation, including X-rays. Detecting and studying this radiation provides valuable insights into the existence and characteristics of supermassive black holes.

Observations have also revealed that some galaxies harbor extremely bright nuclei known as active galactic nuclei (AGN). These active galactic nuclei are powered by mass accumulation onto supermassive black holes. Falling material releases massive amounts of energy in various forms, resulting in powerful outbursts of particles and radiation extending far beyond the black hole.

Intermediate Mass Black Holes

Intermediate Mass Black Holes (IMBHs) are a category of cosmic voids with masses ranging between those of stellar black holes and supermassive black holes. Typically, their groups fall within a few hundred to a few thousand times that of our Sun.

The formation mechanism of intermediate-mass black holes is still not fully understood, making it an intriguing area of research. One proposed scenario suggests that IMBHs could originate from the direct collapse of massive stars or violent collisions of stellar black holes in dense star clusters. Another possibility is that they result from gradually accumulating and merging more minor black spots over time.

Due to their intermediate masses, IMBHs are believed to play a significant role in galaxy evolution. They can impact the dynamics of surrounding star clusters and contribute to the growth of supermassive black holes at the centers of galaxies. IMBHs also offer a potential missing link in our understanding of hierarchical black hole growth, bridging the gap between stellar and supermassive black hole populations.

Discovering and studying intermediate-mass black holes poses a challenge because they are expected to be less common and more complex to observe than stellar or supermassive black holes. Their lower masses make them less luminous, and their signature effects on their surroundings might be more subtle. Nevertheless, scientists actively seek observational evidence of IMBHs using various techniques, including studying the dynamics of star clusters, analyzing the properties of active galactic nuclei, and investigating gravitational wave signals.

The existence of intermediate-mass black holes and their characteristics have important implications for our understanding of black hole formation and galaxy evolution. Further research and observations are needed to confirm their presence and elucidate their role in the cosmic landscape.

What Lies Inside Black Holes?

Black holes are mysterious and fascinating objects predicted by the theory of general relativity, which describes how gravity operates in the universe. Inside a black hole, the known laws of physics break down, making it difficult for scientists to understand what lies within fully. However, based on current theories and knowledge, here’s what we think might be happening inside a black hole:

  • Singularity: At the heart of a black hole is a singularity. This is a point of infinite density where all the mass of the black hole is concentrated. The laws of physics, as we understand them cease to apply here, and our current theories break down.
  • Event Horizon: Surrounding the singularity is the event horizon. This is a boundary beyond which nothing, not even light, can escape the gravitational pull of the black hole. Once an object crosses the event horizon, it is effectively cut off from the rest of the universe.
  • Spaghettification: As an object gets closer to a black hole, it experiences extreme tidal forces due to the massive gravitational field. This process is often referred to as “spaghettification.” In simple terms, the object gets stretched and distorted into a long, thin shape due to the difference in gravitational force acting on different parts of the object.
  • Information Paradox: One of the biggest mysteries surrounding black holes is the fate of information. According to quantum mechanics, information is never truly lost, but if an object falls into a black hole, it seems to disappear, leading to the so-called “black hole information paradox.” Researchers are still trying to reconcile quantum mechanics and general relativity to solve this puzzle.

It’s important to note that our understanding of black holes is still evolving, and there’s ongoing research to explore these enigmatic objects further. Some theories, like the holographic principle and black hole thermodynamics, provide intriguing insights into the nature of black holes and their possible connections to the rest of physics.

In summary, black holes remain one of the universe’s most intriguing and least understood phenomena. The exact nature of what lies inside a black hole is still a subject of active scientific investigation and theoretical exploration.

Other Components of Black Holes

Everything You Need to Know about the Black Holes: One of the Most Mysterious Things in Space
NASA’s simulation of a black hole is shown above. This drawing depicts an accretion disk, a shadow, and a photon sphere. Bottom image: Simulated relativistic jet of a black hole.
  • Accretion Disk: Most black holes are surrounded by intensely hot disks of material, mainly gas and dust from other celestial bodies such as stars and planets. This material falls into the black hole, forming what’s called an accretion disk.
  • Black Hole Shadow: The black hole shadow is a two-dimensional dark region in the celestial sphere formed due to the strong gravitational pull of the black hole. Within this region, a series of photon paths cannot escape the black hole and become trapped within it.
  • Photon Sphere: In the photon sphere, gravity is so strong that light can travel in circular paths. Photons orbit the black hole at the distance of the photon sphere. If an observer were present in this region, they would see their surroundings repeated.
  • Relativistic Jet: Sometimes, matter bounces back from the event horizon after entering the black hole. In this case, bright jets of matter moving close to the speed of light are created. These powerful jets can be observed from great distances despite black holes appearing invisible.

Hawking Radiation and Black Hole Evaporation

Everything You Need to Know about the Black Holes: One of the Most Mysterious Things in Space
Glimpses of Hawking radiation in an artificial black hole (Image credit: newscientist)

Hawking radiation is emitted by quantum phenomena near the event horizon of a black hole. The temperature of black holes is proportional to their mass, as indicated by these radiations.

Although Hawking radiation has not been observed yet, general relativity and quantum mechanics theories provide substantial scientific support. This phenomenon was named after physicist Stephen Hawking, who wrote a paper titled “Black Hole Explosions” in 1974. According to Hawking’s hypothesis on radiation, black holes can emit energy, causing their size to decrease.

When matter falls into a black hole, it cannot escape. This phenomenon can decrease chaos or entropy. Since removing matter reduces chaos, black holes were considered contrary to the second law of thermodynamics. The actual mechanism of Hawking radiation and the emission of particles near the event horizon of a black hole is extremely complex. It requires a comprehensive understanding of mathematics and quantum theory.

However, Hawking’s famous hypothesis about black hole entropy has been confirmed recently, and many misunderstandings related to it have been resolved. Based on Einstein’s theory of general relativity, Stephen Hawking introduced the concept of the black hole area in 1971. According to this hypothesis, the surface area of a black hole cannot shrink over time. Observations of merging black holes and the gravitational waves resulting from this merger validated this hypothesis. According to this conjecture, the area of a black hole formed from the merger of two black holes grows.

Many people believe Hawking’s area theorem contradicts his other hypothesis of black hole evaporation. On the other hand, according to the theory of general relativity, black holes cannot shrink, but they may shrink according to quantum physics.

According to Hawking’s radiation hypothesis, a mist of tiny particles is emitted due to quantum effects near the edges of the black hole, which ultimately leads to the contraction and longer evaporation of the black hole’s lifetime.

Since this evaporation occurs over long periods, it can be said that it does not violate the area theorem in the short term. In any case, there is still much speculation about black holes. However, since black holes are assumed to exist indefinitely, the concept of information loss won’t be affected, as the information within the black hole remains inaccessible from the outside world.

On the other hand, black holes gradually dissipate through the generation of Hawking radiation. This radiation seems not to provide any information about the materials that enter the black hole, resulting in the loss of knowledge forever.

What are Binary Black Holes?

Everything You Need to Know about the Black Holes: One of the Most Mysterious Things in Space
Simulation of binary black holes

Binary Black Holes (BBH) are systems composed of two black holes in close orbits. Binary black holes are categorized into two types: stellar binary black holes, remnants of binary stars, and galactic binary black holes, resulting from galaxy mergers.

Since black holes don’t generate waves, their display is challenging and restricted. However, when two black holes collide, enormous amounts of energy are released in the form of gravitational waves. These waves can be approximated using Einstein’s theory of general relativity. Gravitational waves propagate at the speed of light, curved by massive objects in spacetime.

In 1905, Henri Poincaré introduced the idea of these waves, which Albert Einstein predicted in 1916 using the theory of general relativity. Interest in binary black holes grew during the late 20th and early 21st centuries due to gravitational wave transmission.

Binary black hole mergers are among the most potent sources of gravitational waves in the universe, providing an excellent opportunity to detect these waves directly. If two black holes approach each other, they merge. After merging, a single black hole is created.

In September 2015, stellar binary black holes (and gravitational waves) were fully confirmed. On this date, the LIGO observatory detected GW150914, a gravitational wave resulting from the merger of two stellar binary black holes containing 30 solar masses and located 1.3 billion light-years away from Earth.

The Black Hole at the Heart of the Milky Way

Sagittarius A* is a small, remarkable radio source located at the center of the Milky Way galaxy. This entity can be found near the constellations Sagittarius and Scorpius. Sagittarius A* hosts a supermassive black hole, resembling the massive objects found at the centers of many spiral and elliptical galaxies.

Observations of several stars near Sagittarius A, especially star S2, are used to calculate the mass and upper bounds of the half-radius of this mass. Astronomers determined that Sagittarius A is the supermassive black hole at the center of the Milky Way galaxy based on precise radial boundaries and mass measurements.

Reinhard Genzel and Andrea Ghez were awarded the Nobel Prize in Physics in 2020 for matching Sgr A’s properties with supermassive black holes. On October 31, 2018, the discovery of Sagittarius A was announced. Astronomers found gaseous masses in the Sagittarius constellation moving at 30% of the speed of light.

The speed of star S2 in Sagittarius A’s orbit was estimated at 7650 km/s (2.55% of the speed of light) in July 2018. Assuming general relativity is a reasonable explanation for gravity at the event horizon, radio emissions from Sagittarius A come from a bright spot around the black hole and near the event horizon, or perhaps from the accretion disk.

Sagittarius A* orbits around several stars known as S-cluster stars. Due to dust between the stars severely limiting visible wavelengths, these stars can only be seen in the infrared range of the K band. Stars S62 and S4714 have orbits close to Sagittarius A*. However, a refined idea suggests that by 2021, the observations will provide new insights into the movement of these stars and their interactions with the black hole.

Everything You Need to Know about the Black Holes: One of the Most Mysterious Things in Space
Some hypotheses say that Sagittarius A* may not be a black hole at all.

Is There a Black Hole at the Center of the Milky Way?

A black hole might not be at the heart of the Milky Way galaxy’s center. Instead, the galactic core could consist of dense dark matter. The features of Sagittarius A*, the massive black hole at the center of the Milky Way, are inferred from its gravitational effects on other bodies, like the peculiar orbits of stars near the galactic center. But what if this diagnosis is incorrect?

According to a recent study, if the galactic center is composed of dark matter, there’s a stronger reason to describe the orbits of the galactic center and the initial orbital velocities in the galaxy’s outer regions.

Numerous investigations have been conducted on the orbit of star S2 over the past two decades. This star completes an orbit around the galactic core every sixteen years. Its elongated and elliptical path is believed to be an ideal laboratory for general relativity studies.

Previously, two different teams showed that relativity applies not only to spacetime at the galactic center, but also to a supermassive black hole with a mass four million times that of the Sun. Then came G2, the mass issue.

Compound G2, in an elliptical orbit, exhibited unusual behavior in 2014 when closest to the galactic center. This mass transitioned from being compact and natural to being elongated and extended, then returned to its natural state.

The behavior of G2 was remarkably strange, and its nature remains unknown; however, its orbital movement at the point closest to the black hole showed a type of expansion that contradicts the black hole model, according to the team of astrophysicists led by Eduard Antonio Besra Vegara from the International Center for Relativistic Astrophysics.

Researchers showed last year that S2 and G2 are consistent with a new model: dark matter fermions, sometimes known as darkninos. As this matter is light enough to avoid collapsing into a black hole, it remains as a dense, massive bubble at the heart of the Milky Way, enveloped by a diffuse haze toward its edges.

The only bodies orbiting the galactic center are S2 and G2. Researchers expanded their model to include seventeen other stars from the S-cluster surrounding the galactic center and discovered some intriguing results. These stars confirmed the results they found. According to simulations, the galactic core might harbor a dense bubble of dark matter that grows less dense as it moves outward.

Based on previous discoveries, dark matter is undoubtedly one of the universe’s major puzzles. Its unknown nature is logically attributed to its gravitational effects, which regular matter cannot explain. Stars, dust, and galaxies are examples of regular matter.

If galaxies were dominated by regular matter, they would rotate much faster. The gravitational lensing, or spacetime curvature around massive objects, is much larger than previously believed. This phenomenon causes a double gravitational pull that humans cannot immediately sense.

We only know that dark matter exerts gravitational effects on other objects. Active galactic nuclei, like the supermassive black hole in galaxy M87*, which is about 6.5 billion times the mass of the Sun, are more consistent with the black hole model.

According to researchers, dark matter exceeding critical mass could become a supermassive black hole. This phenomenon helps describe the formation of supermassive black holes, as there is no idea about their size or number formed in the universe’s early stages.

Dark matter comprises nearly 80% of the material in the universe. The count of supermassive black holes and other types is not sufficient to fall into this category; however, researchers don’t yet reveal the origin of these materials. Their approach provides a candidate for dark matter, which also aids in describing the nature of supermassive black holes. Further analysis can bring us closer to the truth.

The Reality of Black Holes and Time Travel

Everything You Need to Know about the Black Holes: One of the Most Mysterious Things in Space

Time travel has always been a hot and intriguing topic for scientists and the general public. Despite many being drawn to concepts like altering the past or glimpsing the future, no one has ever achieved this goal. This ambition has only been realized in science fiction books and movies. In his book “Black Holes and Baby Universes” (1994), Stephen Hawking states:

“The best evidence we have that time travel is not possible and never will be is that we have not been invaded by hordes of tourists from the future.”

There are other speculations regarding time travel beyond the scope of this article, such as wormholes, traveling at the speed of light, and spacetime curvature. Many ideas relate time travel to black holes, which we will explore below.

According to Professor Hawking, a black hole similar in size to the one at the galactic center significantly impacts time and can cause substantial time dilation.

Due to their immense size, black holes can act as natural time machines. On the other hand, the region around a black hole is intensely hot, making it inaccessible with current technology.

But even if one could approach a black hole, what would happen if you fell into it?

Janne Levin, a physics and astronomy professor, has made significant contributions to our understanding of black holes through her research. She takes the audience on a fictional space journey to the heart of a black hole in her book “How to Survive a Black Hole.” Falling into a black hole involves crossing the event horizon, often referred to as the point of no return.

Levin’s novel brings the audience close to the event horizon. The black hole is defined as a solitary dark disk. You can peer beyond the event horizon. In other words, you’re not alone. The event horizon doesn’t provide a barrier for light to fall through, but the dark black hole from the outside can be extremely dangerous.

You can see the world beyond the event horizon through a one-way window to it. You can observe the world’s progress while you can’t stop your descent. Passing through the event horizon, the light from the galaxy paints a quick display of decades, millions, or even billions of years on Earth.

The light that catches your attention reveals everything from the collapse of civilizations to photographers’ cameras and even exploding star ions. When you land, the black hole’s throat narrows, focusing all light into a bright point. You’ll see light at the tunnel’s end, just like the experience of nearing death.

According to scientific and mathematical perspectives and the theory of general relativity, the infinite curvature of spacetime results in singularity where all paths end. Singularity can be defined as a break in spacetime. You will undoubtedly reach singularity. You’ll collapse upon entering singularity. The nearest part of your body accelerates faster than the distant part, resulting in a grim outcome. The anatomy converges and collapses in an instant. You’ll be torn apart and shredded in less than a fraction of a second, shorter than a blink of an eye.

Then, the organic matter of your body gets broken down into smaller parts, until particles of your existence are eventually directed towards pieces of space and time. The end of the road is singularity, and the endpoint in space is time or the last point of existence.

Beyond singularity, there’s no future. Dying in singularity means the end of your existence: the demise of fundamental particles in your body and the eradication of your reality and truth. You’re unreal. In fact, like many other possibilities, singularity shouldn’t be accepted as a foregone conclusion. Despite the impending end of singularity, it must be approached with caution. In the model, singularity might become a burden.

In other words, based on mathematical definitions, the physical definition of relativity collapses at singularity. General relativity can’t tell the complete story of the universe. Perhaps, within the depths of a black hole, remnants of quantum matter that fell due to destructive energies can be accessed instead of singularity. However, this hypothesis still lacks substantial support.

A more prevalent hypothesis built on speculation is that within a black hole, everything collapses into a white hole, much like the new big bang in another part of the universe. Moreover, the inner part of a black hole could be larger than the outside; another world might exist within.

According to existing evidence, a black hole is a dark point in spacetime, and scientists still need to answer the question: Where will we end up if we fall into a black hole? The mystery surrounding the black hole and the event horizon adds to this tragedy’s intrigue.

You’ll die before the big bang happens anyway. Changing your perspective on singularity won’t keep you alive. Your body will decay, yet you might become part of a larger ecological system.

If your body particles aren’t entirely depleted in a singularity state, they might become quantum remnants at a black hole’s center. These remnants might hold hope for the future or even become elements for a new world, and some of them might eventually lead to life and microbial life. As a result, although black holes act as natural time machines, the idea of time travel through a black hole is impractical.

Wonders of Black Holes

  • The Possibility of Supermassive Black Holes (SLAB):

Researchers discussed the possibility of supermassive black holes (SLAB) in September 2020. These objects have a mass a trillion times that of the Sun, which is equivalent to ten times the mass of the largest known black hole, TON 618, with a mass of 66 billion times that of the Sun.

Certain patches originated from the universe’s early days; thus, primordial black holes have left traces in the cosmic microwave background radiation, the remaining light from the early universe (first 380,000 years).

Light bending around distant stars offers unique insights into the effects of colossal black holes. While these black holes remain outside the realm of theory, they have piqued the interest of many.

  • Stars Disturbed by the Black Hole:

When a massive object approaches a certain distance from a black hole, it can be torn apart by intense gravitational forces. Since a cloud of gas and dust surrounds black holes, this process is known as “spaghettification” and is highly unusual.

Using the NTT telescope and the Very Large Telescope (VLT), scientists at the European Southern Observatory witnessed the spaghettification process of a star with unprecedented detail in October 2020.

AT 2019Qiz, a rare event, provides astronomers with penetrating insights into such phenomena, allowing for a better understanding of gravity in edge settings.

  • Black Holes Could Have Wings:

Matter and energy must collapse into an infinitely dense point to form a black hole. As such infinities are physically impossible, theorists sought a solution to this problem for a long time.

According to string theory, which replaces all particles and forces with vibrating strings, black holes could be weirder, morphing into a foggy sphere resembling threads of fundamental strings.

According to research published in October 2020, if neutron star atoms are thread-like, the pressure of these threads results in a sphere akin to a ball made of threads. This concept requires further examination but may present an applicable option to address this boundless problem.

  • The Perils of Black Holes:

According to physicists, every black hole has an event horizon – boundaries from which you can never escape if you fall in. But could there be a black hole without an event horizon, called a naked singularity? If found, this phenomenon could be extremely hazardous, as the laws of physics break down at a black hole’s event horizon, and a naked black hole wouldn’t have a protective barrier.

Most theorists believe that the existence of naked black holes is inconceivable; however, research published in November suggests there might be a way to ascertain this.

You can differentiate between these black holes by examining their accretion disks. An accretion disk is a ring of gas and dust that forms when matter enters a black hole; this feature could distinguish between regular and naked black holes.

Notes and Discoveries about Black Holes

We’re in a golden age of black holes. Using the Laser Interferometer Gravitational-Wave Observatory (LIGO), astronomers have been receiving direct signals from black hole mergers since 2015, and observatories like the Event Horizon Telescope (EHT) captured the first image of a black hole’s shadow.

As black holes don’t emit electromagnetic radiation, astronomers must rely on direct methods to locate these objects. For instance, the gravitational impact of a black hole on surrounding matter can be used to verify its presence.

Discovery of Gravitational Waves

The LIGO (Laser Interferometer Gravitational-Wave Observatory) first directly observed gravitational waves on September 14, 2015. This signal aligned with predictions of gravitational wave theory, resulting from the merger of two black holes, with masses of 36 solar masses and 29 solar masses, respectively.

Until recently, this discovery stood as the most solid evidence of black hole existence. Numerous other gravitational wave events have been observed since 2015.

In 2020, both LIGO and its European counterpart, Virgo, detected immense vibrations in spacetime caused by gravitational waves—phenomena arising when heavy objects oscillate. These observatories have achieved several breakthroughs. However, in May, researchers from both observatories jointly announced the discovery of the largest black hole collision, where one black hole is 85 times the mass of the Sun and the other is 66 times the mass of the Sun. The collision formed a black hole with a mass of 142 times that of the Sun.

Astronomers had previously observed black holes the size of the Sun and identified that supermassive black holes, millions of times heavier than the Sun, exist at the centers of galaxies. Nonetheless, no evidence of intermediate-mass black holes has been found.

The precise origin of black holes remains an enigma scientists are striving to solve. LIGO and Virgo will publish a catalog of hundreds of gravitational wave signals detected between April and September 2019 in October 2020. This catalog will encompass 39 entries.

Measuring Star Movement around Sagittarius A*

Accurate star movements at the center of the galaxy can strongly indicate the presence of a massive black hole. Astronomers have been tracking the motion of 90 stars around the invisible mass of Sagittarius A* since 1995. By linking the speeds of these stars with Keplerian orbits, astronomers have managed to determine the trajectories of the stars closest to the galactic center.

The First Image of a Black Hole

ما هي الثقوب السوداء؟ كل ما نحتاج لمعرفته حول الثقب الأسود أكثر الأشياء غموضًا في الفضاء
The Event Horizon Telescope (EHT), a global network of eight massive radio telescopes, captured this image of a supermassive black hole and its shadow at the heart of the galaxy M87.

Astronomy witnessed a momentous year in 2019. The Event Horizon Telescope (EHT) captured the first direct image of a black hole during this year. This black hole resides at the heart of the M87 galaxy, located 55 million light-years away from Earth.

This image portrays a luminous ring surrounding a central darkness, the shadow of the black hole. But how did scientists manage to image a black hole from such a distance? The marvel of the telescope holds the key to comprehending this image. In fact, the Event Horizon Telescope constitutes a global network of telescopes.

Various challenges were faced in the photographic imaging of black holes. Firstly, black holes are dark entities that don’t emit visible light, thus making them impossible to directly observe. However, this isn’t the sole primary issue with black holes.

Seeing objects of small angular sizes is difficult. So, how was the black hole observable in the night sky? The angular precision of the telescope is determined by two factors: the aperture size and the wavelength of light.

Shorter wavelengths (such as ultraviolet or X-rays) offer exquisite precision; however, a millimeter wavelength of light was employed for the image of a black hole. Compared to visible light, this wavelength is exceptionally long, with the visible light wavelength being 500 nanometers.

Consequently, the only way to resolve the refraction issue was to use a larger telescope. This led to the choice of EHT for capturing this image. The required size of an Earth-based telescope is practically unattainable. Nonetheless, data from several radio telescopes spread across different parts of the planet can be combined into a larger telescope like EHT to achieve results. Naturally, there are drawbacks to this approach. To provide the most accurate image from acquired data, the EHT group employed analytical methodologies.

On the other hand, the image of the black hole was captured using radio waves instead of visible light. Each pixel represents a portion of the radio wavelength.

When you look at the orange regions in the image, you can perceive a false-color representation of the wavelength. Therefore, the image obtained from the recent black hole isn’t a conventional image accessible via traditional telescopes. Nevertheless, it remains a remarkable step forward in astronomy.

This image illustrates Einstein’s theory of general relativity, which posits that gravity results from spacetime curvature. Future images may aid in understanding how black holes function and the significance of supermassive black holes, like the M87 black hole, in the evolution of their host galaxies. However, this doesn’t signify the project’s conclusion. According to EHT Director Shepherd Delman from the Harvard-Smithsonian Center for Astrophysics, current methods can be employed to enhance the accuracy of existing images. Artificial intelligence might eventually be integrated into this field.

Observing the Nearest Black Hole

The nearest known black hole to Earth, Unicorn, is situated 1,500 light-years away and possesses three times the mass of the Sun. This small black hole has a dual-meaning name. It lies within the constellation Monoceros (the Unicorn) and is unique due to its low mass (three times the mass of the Sun).

Accompanying the solitary black hole is a red giant at the end of its life (red dwarfs appear as stars like the Sun die). Over the years, various instruments, including ASAS and NASA’s TESS satellite, have monitored this companion star.

Scientists made an intriguing discovery when analyzing data: the brightness of the red giant regularly fluctuates, indicating the presence of another body affecting this star.

Researchers concluded that the body influencing the red giant is most likely a black hole with a mass three times that of the Sun, based on initial velocity criteria and variations in the star’s brightness. The black hole bends the neighboring star into an elongated football shape, much like the Moon’s gravitational effect on Earth’s tides.

Light Behind the Black Hole

Due to the immensely strong gravitational and magnetic environment around black holes, it’s possible to observe light bending around and being reflected from behind the black hole, according to Einstein’s theory of general relativity. In one of the latest findings, astronomers directly detected this bent light in the form of X-rays from a supermassive black hole located 800 million light-years away for the first time. This black hole was found in the galaxy l Zw 1.

An accretion disk exists within an active black hole like l Zw 1*. The strong magnetic field expels electrons from atoms, resulting in the formation of magnetized plasma.

The corona lies outside the event horizon of an active black hole and on the inner edge of the accretion disk. The black hole’s magnetic field amplifies heated electrons in this region.

The magnetic field distorts and emits in a typically connected and disconnected manner. In the Sun, this mechanism leads to enormous solar flares, but in a black hole, the corona acts like a synchrotron, accelerating electrons to points that emit X-ray wavelengths.

A portion of X-ray photons causes the accretion disk to glow, and it’s recovered through processes involving photoelectric absorption and re-emission, considered reflection in the X-ray spectrum. This reflected radiation can be used to image areas close to the black hole’s event horizon.

In Conclusion

The inner workings of black holes remain an enigma. At the heart of a black hole lies the singularity—a region of infinite density and spacetime curvature—where our current understanding of physics breaks down. The singularity is surrounded by the event horizon, beyond which nothing can escape the gravitational pull of the black hole.

The precise nature of what lies inside a black hole is still unknown. The singularity is often regarded as a point of infinite density, while other theories suggest the possibility of quantum effects or exotic forms of matter within black holes. However, these ideas remain speculative, and further research and advancements in theoretical physics are needed to unveil the true nature of the inside of a black hole.

Black holes continue to captivate the attention of scientists and inspire ongoing research. Observational and theoretical studies of black holes provide valuable insights into the fundamental laws of the universe, gravity, and the mysteries of spacetime. As our understanding evolves, we hope to gain a deeper comprehension of these cosmic enigmas and the secrets they hold.

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