What are black holes? Well, if you ask any scientist to answer this question for a layperson, they’re probably going to say something along the lines of, “Black holes are the most fascinating and strangest phenomenon in space. They are really mysterious and weird objects that have been the point of study for years.”
And, to be honest, that’s possibly the best way to answer that question without getting into all the mind-bending physics of black holes.
Black holes are known to be extremely dense with unimaginable gravitational attraction. Their mass, and by extension, their gravitational pull, is so strong that even light cannot escape if it comes too close, which is where these monstrosities of space-time get their name from. Albert Einstein was the first one to predict their existence in 1916 in his theory of relativity. But the name ‘Black Hole’ was coined in 1967 by John Wheeler. They were just recognized as theoretical objects until the effects of the first black hole were observed in 1971.
What are Black Holes?
A black hole basically forms when a lot of matter or energy is condensed into an infinitesimally small space. How small does this space need to be? Well, if you wanted to make the Earth into a black hole, you’d have to compress the ENTIRETY of the Earth into the size of a peanut. Now, that might not be possible for something like the Earth, but more massive objects like stars can become black holes when they reach the end of their lives.
The Event Horizon Telescope (EHT) recorded the first-ever image of the black hole (featured above) in 2019. The image is of a black hole in the very center of the M87 galaxy. The telescope was trying to examine the area where nothing can escape from the gravitational pull of the black hole. The image shows the sudden loss of particles of lights (also known as photons). Now that astronomers know what a black hole looks like, more research possibilities have been opened to them.
Types of Black Holes
So far, three types of black holes have been documented: stellar, supermassive, and intermediate.
Stellar Black Holes
When the fuel source of a star has completely burned out, the object can fall into itself or completely collapse. Smaller stars, which are still around three times the mass of our sun, turn into white dwarfs or neutron stars. However, when more massive stars collapse, they continue to compress. This creates a stellar black hole.
Stellar black holes are created when individual stars that are small but dense collapse. These objects have the ability to compress three times the mass of the sun into barely the size of a city. This creates an insane gravitational pull that can pull on other objects around it. They continue to consume gas and dust from their surroundings, which helps them continue to grow in size.
It’s been suggested that there may be thousands of such black holes in the milky way alone.
Supermassive Black Holes
Supermassive black holes dominate the universe. They are enormous in size – millions or billions of times the mass of the sun. They have been theorized to lie at the center of every galaxy, including ours.
Scientists have been trying to narrow down the reasons why such black holes spawn in the first place. Once the giant black holes form, they begin to devour astonishing levels of mass from their surroundings. This includes gas and dust, which exists in considerable quantities in every galaxy. It allows them to grow to a gigantic size.
Supermassive black holes are thought to be the result of hundreds to thousands of small black holes merging together. Another possible reason can be that large gas clouds may collapse together, which means that a lot of mass quickly collapses into a small space – thus forming a huge black hole.
More theories suggest that stellar clusters may collapse, falling together to create a massive black hole. Supermassive black holes can also be a product of huge clusters of dark matter coming together. However, since dark matter doesn’t emit any light, it is difficult to study or observe. This means that this theory is difficult to prove at best.
Intermediate Mass Black Holes (IMBH)
Scientists had previously only differentiated between large and small-sized black holes. However, recent research shows that there can also be many intermediate or mid-sized black holes.
Such black holes are created when a cluster of stars collide, creating a chain reaction. If these IMBHs form for the same reason, they can collapse together at the very center of the galaxy to form a supermassive black hole.
The first intermediate black hole was discovered in a spiral galaxy in 2014. In 2018, new research suggested that IMBHs can be found in dwarf galaxies in the universe. When ten such small galaxies were observed, scientists received X-ray activity. This is an indicator that such black holes may exist in these galaxies.
What Do Black Holes Look Like?
What do black holes even look like? This is hard to tell since they do not emit any light at all. They are just strange regions in space where the gravity has gotten so strong that it warps space, bends light, and distorts time.
Black holes have three main layers: the outer event horizon, the inner event horizon, and the singularity. The event horizon is the main boundary around the black hole’s mouth through which light doesn’t escape. Once any particle, gas, or dust enters this event horizon, it cannot leave due to the extreme gravitational force of the black hole.
The region on the inside is called the singularity, where the mass of any object lies. This is the single point in time and space where all the mass is concentrated.
Scientists are unable to truly see the back hole like they can with other objects in space. This is due to the fact that black holes tend to bend light, making it harder to observe them. Astronomers can only ‘see’ black holes by detecting the massive amounts of radiation they emit when gas and dust are drawn in by the gravitational pull. They can also observe the gravitational effects of black holes on the objects around them. This is how black holes were discovered in the first place.
Supermassive black holes can even become entirely covered by thick quantities of gas and dust. So, even if there are some telltale emissions, they may get blocked by this thick layer.
As matter falls into black holes, it can also ricochet off the two event horizons on occasion. This can push it to hurl outward rather than moving further toward the singularity. These jets of mass can travel at near the speed of light. While we cannot directly see the black hole itself, we can observe these jets.
Black holes are a fantastic phenomenon that needs to be researched in more detail. They are mysterious objects that have been the topic of questions from the broader scientific community. The study of these wonders of nature has led to countless discoveries in the fields of physics and astronomy. So, what are black holes? The answer to that question is, “we don’t know,” but with time and more research, we’ll one day discover the mysteries lurking within these monsters of space-time.