Since time unknown, black holes had been one of the greatest enigmas of the cosmic world. Black holes are like giant cosmological baskets that accept everything that manages to fall into them and never let them escape. Decades have passed since their discovery, yet they hold a special fascination among humankind. Even world-renowned physicist Stephen Hawking couldn’t resist their mysterious charm and once lost a wager over the black hole Cygnus X-1. By the way, do you know that our very own Milky Way Galaxy has a supermassive black hole at its center? Keep reading this article to learn 10 Unbelievable Facts about Black Holes.
1. Black holes do not suck in objects. They have an extremely strong gravitational force which is almost impossible to overcome by any object that comes too close to it. If our Sun was replaced with a black hole of equal mass, the planets would orbit around the black hole as they orbit the Sun today.
In popular media, black holes are depicted as space entities that act as vacuum cleaners by sucking everything near it in. But this is not true. Actually, black holes are an extremely dense point in space that leads to deep gravity sinks. The gravitational force of this region is so strong that even light cannot escape. Anything, be it a planet or star, that ventures close to it immediately falls into a gravitational tug-of-war. But the object must be fairly close to the black hole to lose this tug-of-war and fall into it.
To understand the concept better, imagine replacing our sun with a black hole. One might think that all the planets and moons would be sucked into it immediately. But if the black hole is of similar mass as our sun, then all planets would continue to orbit around it absolutely unperturbed. The only thing that will change is the temperature and brightness as the planets will be quite less warm and illuminated. (1, 2)
2. Black holes come in all sizes ranging from stellar to supermassive. They can grow throughout their lives and can eventually evaporate over time as a result of Hawking radiation.
The starting size of black holes varies depending on their source of inception. The stellar black hole originates when a large star collapses and continue to compress. The stellar black holes are relatively smaller than others but incredibly dense. The intermediate black holes are mid-sized. They form when stars in a cluster collide in a chain reaction. Several of these can form in the same region eventually falling together in the center of a galaxy creating a supermassive black hole. Our own galaxy, the Milky Way, has its own supermassive black hole at its center. After formation, these black holes keep gathering gas and dust around them. Since these materials are available in plenty in the center of galaxies, the black holes grow to enormous sizes.
Black holes do not keep on growing forever. In 1974, Stephen Hawking theorized that black holes radiate some particles, mainly photons, through a process called “Hawking Radiation.” Due to Hawking radiation, black holes keep on losing mass and began shrinking. This is an extremely slow process. It is so slow that a black hole with the mass of our Sun would take 1067 years to evaporate completely. (1, 2, 3)
3. Light bends so much near black holes that if you were near one and looking away from the hole you could actually see the back of your own head!
The extreme density of black holes ensures that not even light escapes from it. Light traveling near black holes immediately gets absorbed into it. But scientists have found that there is a point close to the black hole where light would not get lost. The light traveling at this point should be just slow enough to be caught by the gravity of the black hole, but should also be just fast enough so that it doesn’t get pulled into the black hole. If light can reach this point and at the exact speed, then instead of getting lost into the black hole, it will start orbiting the black hole. This point is known as the “photon sphere.”
Theoretically, if a person is at this point and turns his head to the side so that he is no longer facing the black hole, then light bounces off the back of the person’s head, orbits the black hole, and comes all the way back allowing the person to see the back of their head.(1, 2)
4. The process of getting torn apart by a black hole is called “Spaghettification.” The tidal forces inside a black hole are so strong that they will stretch the human body into a long thin noodle of composite atoms as the person descends into it.
Have you ever thought what would happen if a person ever descended into a black hole? According to astrophysicists, the person will become an actual human spaghetti. Black holes possess extreme tidal forces. When a person enters a black hole’s event horizon, the first thing he will feel is the sensation of being pulled apart. This occurs due to the strong gravity and low gradient of gravity inside the black hole. These factors will start stretching the person in an unpleasant manner.
If the person falls feet first into the black hole, then the gravity at their feet would be stronger than at their head. So, the person would be stretched vertically. Also, the right side of the body will be pulled to the left and vice-versa, compressing the person horizontally. The vertical pull and horizontal compression will turn the person into a human spaghetti. That’s why this process is called spaghettification or “the noodle effect.” (1, 2)
5. Black holes can sometimes eject stardust falling into it in long and bright radiation-laden burps.
In 2011, astronomers observed a burst of high-energy gamma rays. It was ejected from the center of a dwarf galaxy situated 3.8 billion light-years away. In visible light and infrared wavelengths, it was as bright as a hundred billion Suns. According to astronomers, the gamma rays radiated were the result of a star being shredded by a black hole. The star got too close to the black hole and was unable to escape its gravitational pull. The supermassive black hole that was shredding the star was ten million times the mass of the Sun.
As the star fell into the black hole and neared its maw, it heated up along the way producing a burst of energy. This energy emerged as huge amounts of bright radiation. Supermassive black holes are present at the center of most large galaxies, but events such as a “stars getting eaten” in a galaxy rarely happens, only maybe once every hundred million years. (source)