Ever felt intrigued by black holes after watching movies like Interstellar or Star Trek? Black holes have always been one of the most mysterious topics in the history of mankind. A lot of theories and several debates have happened around the topic of black holes. But, there is a still we don’t know about the black holes. In this post, my friends and guest blogger, Sujoy, will try to put some light on the fundamentals of the black holes facts.
Black holes are some of the most perplexing objects in the entire Universe. Stephen Hawking, who died this year, helped give more solid mathematical backing to the concept of black holes, the existence of which was predicted by Albert Einstein’s 1915 theory of general relativity.
According to Wikipedia, a black hole is a region of space-time (that looks like a space whirlpool) that exhibits such strong gravitational effects that constitute a point of no return for anything that falls inside. In fact, black holes are so dense, where gravitation is so strong, that nothing, not even light, can ever escape from it.
Now, over to Sujoy!
Black Holes Facts
by Sujoy Sengupta
Introduction on Black Holes
Renowned philosophers, mathematicians, intellectuals, thinkers of the ancient and medieval period had their view that earth is flat. With the progress of space technology scientists of the later period found and proved that earth is a spheroid. Now we know that earth is a one-off planet in a big solar system. With the advent of the powerful telescope, we can observe and study not only our solar system but also beyond it.
With the help of modern ground-based telescope and Hubble’s telescope (named after famous Astro-physicist Edwin Hubble) which is orbiting around the earth, we came to know that our solar system consisting of 9 planets including earth is situated at one portion of a huge galaxy called the milky-way galaxy. It will be hard to contemplate that it will take roughly one lakh year to travel from one end of this galaxy to the other end even with the speed of light, that’s how big it is. But with the aid of the advanced telescope, we can see to every nook and corner of this galaxy and consequently we have found strange objects scattered within this galaxy.
Nature & Origin of Black Holes
Black holes are massive and they contained dense mass. They have gravity so strong that not even light can escape from it. Black holes have the exclusive ability to trap light only by using its gravitational force. About the origin of the black hole, the scientists believe the following.
At a time the corpse of a massive star collapses on itself. As a consequence of this, the whole mass becomes very dense. As a result of this, it warps the fine fabric of space and time. In the black hole, there is a space called event horizon. It has another name which is the point of no return. If any matter crosses this point it will rotate helplessly with an unknown fate. Extensive research has been done on the black holes for decades. In spite of all research, many of the facts of this cosmological phenomenon remained in dark. It is still a mind-blowing phenomenon for any scientist.
Types of Black Holes
There are mainly three types of black holes. Stellar-mass black holes and supermassive black holes are quite common. Stellar-mass black holes are generally 10 – 24 times as massive as the sun. Whereas, the supermassive black holes are million times as massive as the sun. Besides this, there are other intermediate black holes which fall between the above two.
Few Well Known Black Holes
The names of some famous black holes which deserves special mention are Cygnus X-1, Sagittarius A, M87, Centaurus-A.
Cygnus X-1 is a combination of stellar-mass black hole and an X-ray source. It is located at a distance of about 6,500 light years away from the earth. It has a composition of blue supergiant variable star and the X-ray source. Scientists believe that the X-ray source is the black hole.
Sagittarius A is a super-massive black hole. Sagittarius A is situated at the center of the Milky Way galaxy. It lies towards constellation Sagittarius. The black hole has a mass equivalent to about 4 million suns.
M-87 is an elliptical galaxy. At its center there lies a black hole which has a mass equivalent to about 3.5 billion times of our sun. This black hole is encircled by superheated material that took the shape of a disk. This jet of superheated material is rushing out of the black hole at a very high speed. It is covering a distance of about 5000 light years from the galaxy’s core.
Centaurus A – If we look towards constellation Centaurus there is another galaxy named Centaurus A. It is a gigantic spiral-shaped galaxy containing a highly active nucleus. The nucleus is nothing but a black hole. The magnitude of this black hole in terms of mass is 55 million times of our sun. Two jets of superheated material can be seen streaming away from the core of this galaxy (i.e from the core of black hole) covering a distance of about a million light years in space. It is having a velocity equivalent to half the velocity of light.
Characteristics of Black Holes
The gravitational force of a black hole is so extreme that it can distort space & time in its adjacent vicinity. If you move too close to a black hole your time will run slow. Any substance that gets too close to a black hole will get sucked in by its extreme pulling power having no chance of escaping.
A huge amount of gas, dust, stars, and planets after being assembled together taking a form of disk orbit the black hole. This disk may be called the accretion disk.
There is a region that surrounds the circular black hole. It is the border between the black hole and the outer space. This region may be called the point of no return or event horizon named by the scientists. The rotating material around the black hole has an angular momentum. In this region, the massive gravitational pull of the black hole overpowers the momentum of the material. As a result of this, the material crosses the event horizon. If any material crosses this event horizon it will encounter a tremendous gravitational pull from the black hole and ultimately it will be lost with an unknown fate.
The fact that black holes exist was first proposed by a scientist in the 18th century. After that, no remarkable improvements were observed in its exploration until 1964 and remained a mathematical curiosity. In the year 1964 scientists found the first black hole namely Cygnus X-1. Towards the direction of the constellation, Cygnus scientists discovered a beam of X-ray which proves the presence of the black holes in that direction.
Black holes do not have the ability to emit any kind of electromagnetic wave. The surrounding materials of a black hole like gas, dust, stars, planets etc. present in the accretion disk gets heated. These superheated materials emit radiation which is the indicator of the presence of a black hole. The other adjacent objects of a black hole are very much affected by the immense gravitational force of the black hole. This is another cause of electromagnetic radiation.
The center of the black hole is known as the singularity. The standard laws of physics have no validity in this region. The singularity of a black hole can create an altered Universe.
If a person remains alive in a black hole he would first feel weightlessness and then an intense feeling would follow up. If he gets in close proximity towards the center of the black hole he would feel tidal gravitational forces. He will feel a stronger pull and ultimately he will be stretched and ripped apart. During falling he will see distorted images due to the bending of light rays around him. As he continues to go deeper into the black hole he will still be able to see images from outside the black hole because light from outside will continue to reach him.
Many facts about the black holes are still unexplored. Due to the constant efforts and endeavor of the scientists we know many facts about black holes. Hopefully, in the future, we shall know more about these cosmological dense monsters.
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Featured Image Source: Phys.org