Black Hole

 

    Since the beginning people on Earth were curious to understand the universe. What structures are present in our universe and their details? So in this article, I will try to mention the details of the most mysterious objects called Black holes. Firstly, Einstein in his theory of relativity predicted black holes, and first time in 2019 we captured the first image of a black hole named M-87. I will try my best to explain the concepts very simpler so that one can easily understand it.

Let’s start with what is black hole A black hole is a region in space where gravity is so strong that nothing, not even light, can escape its gravitational pull. It is formed when a massive star collapses under its own gravity during a supernova explosion. The collapse causes the star's matter to become extremely dense, creating a gravitational field that is incredibly intense. Now let’s discuss briefly how black holes are actually formed. When a star that is more massive than the  Sun has burned all of its nuclear fuel, its core will begin to contract under the force of gravity. This contraction generates heat, which causes the surrounding layers of the star to expand and cool. As the core continues to contract, the temperature and pressure in the core will increase. Eventually, the core will become hot and dense enough to ignite helium fusion, where two helium nuclei combine to form beryllium. This process generates a lot of energy, which causes the star to expand and become brighter. Once helium fusion begins, the star will enter a new phase of its life known as the red giant phase. During this phase, the star will continue to expand and cool, eventually becoming so large that it may engulf nearby planets. As the star continues to fuse heavier elements, the core will eventually become composed of iron, which cannot undergo further fusion without absorbing energy instead of releasing it. Since the core cannot support itself, it will collapse rapidly under the force of gravity, producing an enormous amount of heat and pressure. This sudden collapse of the core will generate a shock wave that travels outward through the layers of the star. When the shock wave reaches the outer layers of the star, it will cause a massive explosion known as a supernova. The supernova explosion will release an enormous amount of energy, including light, heat, and radiation, and it will also produce heavy elements such as gold and platinum. The remaining core of the star will either collapse into a neutron star or a black hole, depending on its mass. While stars with initial masses above 25-30 solar masses will likely form black holes. The singularity is a point at the center of a black hole where the mass is thought to be infinitely compressed into an infinitely small volume. It is a region of extreme density and gravitational curvature where the laws of physics as we currently understand them break down. According to general relativity, the singularity is a point of infinite spacetime curvature, where the laws of physics as we know them cease to apply. The event horizon is the boundary of a black hole beyond which nothing, including light, can escape. Once an object or particle crosses the event horizon, it is destined to be pulled into the black hole's singularity at the center. The size of the event horizon is determined by the mass of the black hole. The larger the mass, the larger the event horizon. An accretion disk is mostly composed of dust and gas clouds that orbit a black hole These clouds are captured by other nearby stars by the black hole's gravity. They move faster around the black holes releasing radiation including X-rays. As many people thought that black holes are holes they are not holes fact they are black objects.

There are basically 3 types of black holes stellar black holes, intermediate-mass black holes, and supermassive black holes. Stellar black holes are formed from the remnants of massive stars that have undergone a supernova explosion. When a massive star exhausts its nuclear fuel, it collapses under its own gravity. If the core's mass is above a certain threshold, known as the Chandrasekhar limit (around 1.4 times the mass of the Sun), the collapse continues, and a stellar black hole is formed. Stellar black holes typically have a mass ranging from a few times to tens of times the mass of our Sun. Intermediate-mass black holes (IMBHs) are believed to have masses ranging from a few hundred to several thousand times that of our Sun. The formation mechanism of IMBHs is still a topic of ongoing research, but they could be formed through the collisions and mergers of smaller black holes. Supermassive black holes are the largest type of black holes, with masses ranging from millions to billions of times the mass of our Sun. They are thought to exist at the centers of most galaxies, including our own Milky Way. The exact formation process of supermassive black holes is still being studied, but they are believed to grow over time through accretion of mass from their surroundings and through mergers with other black holes.

The black hole also played a role in the discovery of gravitational waves. The discovery of gravitational waves is directly connected to black holes and has provided groundbreaking evidence for their existence and properties. Gravitational waves are ripples in the fabric of spacetime caused by the acceleration of massive objects. They were first predicted by Albert Einstein in his theory of general relativity in 1916. The detection of gravitational waves was a major milestone in astrophysics and was achieved by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015. The LIGO detectors are sensitive instruments that can detect tiny disturbances caused by passing gravitational waves. One of the most significant findings from LIGO's observations was the detection of gravitational waves generated by the merger of two black holes. This discovery, announced in 2016, provided direct evidence of the existence of black holes and confirmed the predictions of Einstein's theory of general relativity.

There are different black holes that are under study few of them are discussed here. M87 Black Hole is  Located in the center of the M87 galaxy, M87 is one of the most extensively studied supermassive black holes to date. It gained global attention in 2019 when the Event Horizon Telescope (EHT) collaboration captured the first-ever image of a black hole. The image revealed the silhouette of M87 and confirmed the existence of the event horizon, providing remarkable evidence for the predictions of general relativity.  TON 618 is a supermassive black hole situated in a quasar in the constellation Canes Venatici. It is estimated to have a mass approximately 66 billion times that of the Sun, making it one of the most massive black holes known. Its immense size challenges our understanding of black hole formation and growth mechanisms, and it serves as an intriguing object for studying the properties of supermassive black holes. Sagittarius A Situated in the center of our Milky Way galaxy, Sagittarius A (Sgr A) is a supermassive black hole. Although it does not emit significant amounts of visible light, its presence is inferred from the orbital motion of the stars surrounding it. Observations and studies of Sgr A contribute to our understanding of the dynamics of black holes and their interactions with surrounding matter.

Physicist Stephen Hawking also searched a lot on the black hole. He introduced various concepts one of them is hawking radiations. Hawking radiation is a theoretical concept. It suggests that black holes can emit particles and radiation over time. According to quantum mechanics, the vacuum of space is not truly empty but filled with virtual particle-antiparticle pairs that constantly pop in and out of existence. Normally, these pairs quickly annihilate each other, leaving no observable effect. However, near the event horizon of a black hole, one of these particles can fall into the black hole while its partner escapes into space ( particle having more energy and momentum escapes from event horizon) . This happens because the strong gravitational pull of the black hole can separate the particles before they can annihilate. When this occurs, the particle that escapes into space is considered real, while the one that falls into the black hole is effectively lost. This process results in a net loss of mass for the black hole and is known as Hawking radiation. The escaping particle appears to be emitted as radiation from the black hole, carrying away energy and causing the black hole to gradually lose mass over time. The radiation is called Hawking radiation and is believed to have a thermal nature, meaning its properties are similar to those of radiation emitted by a hot object.

Black holes are still a topic under research and study many physicist like Doctor kip throne and Doctor Michio Kaku are doing research on black holes.