What are Black Holes?
Black holes are some of the most mysterious objects in the universe. They are regions of extremely high density and gravity, where nothing, not even light, can escape. Despite their reputation, black holes are incredibly normal in the grand scheme of the universe. Due to the immense forces present near such objects, they form in varieties of different ways, with a wide range of properties, and have consequences on the wider universe around them. To understand how these wonders of the universe form, behave and influence the wider cosmos, one must first look at the world of black holes.
Formation of Black Holes
To form a black hole, an object needs to compress itself extremely tightly. The formation of a black hole is usually due to the gravity of a massive star, called ‘stellar’ black holes. When the star dies, its nuclear fuel has been used up and it can no longer hold itself up against the immense gravitational forces it’s created. As a result, it collapses into itself, compressing its matter deeply until a black hole is created.
Alternatively, other objects or intersections of immense forces, such as colliding asteroids in space, can cause the same effect. Larger black holes, such as ‘supermassive’ black holes, form when two galaxies collide, and the gravity of both galaxies is so great it causes a collapse and the creation of a larger black hole.
Types of Black Holes
The different ways in which a black hole is formed determine its properties and size. There are four main types of black holes that are seen in the universe:
Stellar Black Holes: These are the most common type of black holes, formed when a dying star starts to collapse in on itself. They can range in size from 5-15 times the mass of our sun and form the foundation of many theories on how galaxies are formed.
Supermassive Black Holes: These types of black holes range in mass from millions to billions of times the mass of our sun and are usually found at the centre of galaxies. They are usually the result of mergers between galaxies and in some cases, large stellar black holes.
Micro Black Holes: These are the smallest of the four types and are most often the result of collisions between other objects in space. They are incredibly tiny and evaporate quickly due to their small size.
Intermediate Black Holes: These are the least common type and form when two massive stars, about 20 times the mass of our sun, collide and cause gravitational collapse.
Properties of Black Holes
All black holes have differing properties, depending on the mass of the collapsed object that created it. These properties include:
•Singularity: This is the most fundamental property of all black holes. It is a point of near-infinitely high density at the centre of the black hole, which means everything inside the ‘event horizon’ – the point of no return – is inevitably dragged inwards to the singularity.
•Gravitational Lensing: This is a phenomenon in which light is bent as it passes near a black hole, forming an ‘Einstein Ring’ and resulting in multiple, distorted images of a single object in the sky.
• Spin: All black holes are spinning, either super-fast or less rapidly. The spin of a black hole is determined by the spin of the object that created it, and rotating black holes can create incredibly powerful jets of energy.
•Accretion Disk: This is the gas and dust that surrounds the black hole, which is caused by objects floating in close enough proximity to be pulled in by the black hole’s gravitational pull. This disk glows brightly from the friction created by the objects falling in.
Consequences of Black Holes
The existence of black holes has had a huge impact on the wider universe. Although most people know that nothing can escape a black hole’s event horizon, there can be some intense consequences caused by their presence in the universe. These include:
• Gravitational Effects: A black hole’s immense gravity can cause huge disruptions to the orbit of any planet, star or galaxy nearby. It can cause stars to travel towards the black hole and ultimately be consumed, or could alter the trajectory of a planet, sending it careening into space.
• creation of Galaxies : It is thought that supermassive black holes at the centres of certain galaxies could be providing the energy and gravitational pull that give them structure. Depending on their size, a black hole could also be responsible for creating jets of energy that feed into its host galaxy.
• Energy Sources: Because of its immense power, a black hole’s gravitational forces could be harnessed as an enormous energy source, if it could ever be tapped effectively. Although vastly more energy is produced by a black hole than what can be taken away, scientists are researching ways to harvest this energy.
Black holes are renowned for their dense properties and immense power, but their effects on the wider universe should not be overlooked. Many galaxies would not exist without their gravitational and energy forces, while new galaxies are created due to their immense power. The influence and different ways in which they form gives each black hole unique properties, and these same properties inform the consequences they have on any objects nearby. Though they may be hard to access and understand, the world of black holes is an incredibly fascinating and remarkable field of study.