A REVIEW ARTICLE ON BLACK HOLE A MYSTERY IN THE UNIVERSE

Research Journal of Pure Science, Vol. 2, No. 1 (2015), 34-43 ISSN 2348-5361
34
A REVIEW ARTICLE ON
BLACK HOLE: A MYSTERY IN THE UNIVERSE
MRIGANKA NARAYAN DAS*
Research Scholar, Department of Education, Vinaya Bhavana,Visva-Bharati
Assistant Teacher, Makhaltore Madhyamik Vidyalaya,
Makhaltore, Kalikapur, Burdwan, Pin 713502.
E-mail: mriganka1981@gmail.com. Mob. 09832904623
ABSTRACT
The present research work has been conducted to study the basic characteristics about the black
hole- its historical background, basic concept, different types, formation, general views etc. The
data have been collected from different research papers, books, reports and different websites.
The data are analyzed critically with logical approach considering various factors related with
the black hole. The study reveals that black holes are like celestial monster in the universe. Black
hole may cause a little bit concern for the mankind to survive in this beautiful earth though the
probability that we all are sucked by the black hole is very small at this present time. So there is
no need to fear too much for getting spaghettified soon.
KEY WORD: Black hole, Spaghettification, Schwarzschild radius, Maelstrom
INTRODUCTION
HISTORICAL BACKGROUND
The term ‘black hole’ was first introduced by an American physicist J.A. Wheeler because
everything, including the light wave and any electro-magnetic wave , that went into its zone
was not able to get out and consequently it was appeared as black. In the 18th century,
Laplace and Michell hypothesized for the first time that there exist an astronomical body
with a massive mass that was able to cause an escape velocity greater than the speed of
light in vacuum for which no light was able to resist the strongest gravitational force
generated by this celestial body to escape from it. Actually, the idea of a so massive body that
even light could not escape was first introduced by John Michell in a letter written to Henry

Mriganka Narayan Das/ Review Article on Black Hole: A Mystery in the Universe
35
Cavendish in 1783 and in 1796, a mathematician Pierre-Simon Laplace promoted the same idea
in the first and second editions of his book ‘Exposition du système du Monde’.
This hypothesis was supported by the corpuscular theory of light but not by the wave theory of
light. On this account, the concept of black hole was abandoned at that time. But some months
after the publication of General theory of relativity by the great Einstein in 1916, the black
hole was again become famous because the theory of general relativity predicted that a
sufficiently huge and compact mass can deform space-time to form a black hole.
In 1919, Eddington on the occasion of a total solar eclipse, measured the deflection of
light by the sun coming from a remote star when light passed near the sun. He deduced
that in place of the sun, a sufficiently massive celestial mass should have produced so
great deflection of light that it could not able to pass by. The first modern solution of general
theory of relativity that would suggest a black hole was found by Karl Schwarzschild in 1916,
although its interpretation as a region of space from which nothing can escape including light
was first introduced by David Finkelstein in 1958. In 1916, Karl Schwarzschild calculated that
the black hole should have possessed huge mass because of its small radius ( R=2GM/C2
,
where G=Universal gravitational constant, M= Mass of the black hole, C= Speed of light in
vacuum ) and consequently in order to have an acceptable value of radius, a very
massive mass was necessary.
ACTUALLY WHAT IS A BLACK HOLE
Most people think that a black hole is a massive whirlpool in space, sucking in everything
around it. But that is not the whole story. A black hole is a region in space where gravity is so
strong that the escape velocity is faster than the speed of light. But what does it mean, exactly?
Gravity is what keeps all the things on the earth, but it can be overcome any way. If someone
tosses a coin up in the air, it will only go up a little ways before the earth’s gravitational
attraction slows down it and pulls it back to the earth. If the same is thrown a little harder, it goes
faster and higher before coming back down. If someone could throw the coin hard enough with
the velocity more than the escape velocity of earth then the earth’s gravity could not slow it
down enough to stop it. The coin would then escape from the earth.
Thus, a black hole is a region in space with so much gravity that not even lights (the fastest thing
around) can escape, hence the name. To an observer it will just appear as a sphere of perfect

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black. At the centre of a black hole is an object called a singularity, a point of zero size and
infinite density. A black hole is an object for which nothing can have a high enough escape
velocity to become free from it.
Fig 1: Illustration of a young black hole, spotted recently by the Spitzer Space Telescope.
Source: NASA/JPL-Caltech
DIFFERENT TYPES OF BLACK HOLE
Stellar black holes: It is small but not deadly. When a star burns almost completely, it may
find itself collapsing. For smaller stars (up to about three times the sun's mass) the new star will
be a neutron star or a white dwarf. But when a larger star collapses, stellar black hole may be
created.
Black holes are formed by the collapse of individual stars which are relatively small, but
incredibly dense. Such an object of about ten times the mass of the sun is concentrated into a
city-size range (about 30 km). This leads to a massive amount of gravitational force pulling on
objects around it. Black hole consumes the dust and gas particles from the galaxy around them,
and grows in size.
Super-massive black holes
Small black holes are the maximum in number in the universe, but their cousins, super massive
black holes, dominate. Super-massive black holes are millions or even billions of times as
massive in mass as the sun, but only have a radius similar to that of sun. Such black holes are
assumed to exist at the center of pretty much every galaxy, including the Milky Way.
Intermediate black holes

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Recent research has revealed the possibility for the existence of midsize, or intermediate black
holes. Such black holes could form when stars in a cluster collide in a chain reaction. Several of
these forming in the same region may fall together in the center of a galaxy and create a super-
massive black hole.
Micro black hole
Micro black hole are those which have the mass equal to the about mass of the moon but have
size of about 0.1 mm. These are very small in size compared to others.
CLASS MASS SIZE
Super massive black hole ~105
–1010
MSUN ~0.001–400 AU
Intermediate mass black hole
~103
MSUN ~103
km REARTH
Stellar black hole
~10 MSUN ~30 km
Micro black hole
up to ~MMOON up to ~0.1 mm
FORMATION OF A BLACK HOLE
Naturally occurring black holes form when stars collapse into single mass. Stars are very
massive. Our nearest star, the sun, is roughly 1300000000 km wide and its weight is about
2000000000000000000000000000000 kg or 2×1030
kg. Due to their enormous mass they exert
extremely huge amount of gravitational force. As we know that gravity is related to mass by the
following equation
F = GM1M2 / r2
where F is the force, M1 and M2 are the two masses, r is the
distance between their centre of masses.
This is the Newton’s Law of Gravitation. The value of the constant G is 6.67428×10-11
M.K.S
unit which is quite small, however when we put the mass of the sun and the earth and the
distance between them then the force comes out is 3.76×1022
N, which is very large.
When the force due to gravity of a big star becomes bigger than the outwards pressure caused by
its temperature then the force causes to make the star collapse, pulling all its mass inwards to a

38
central point. This central point becomes smaller and denser as all of the mass of the star is
squashed into a tiny point.
Not all collapsing stars form black holes however. For an example if we want to turn the earth
into a black hole we have to compress it to about the size of a large mosquito, and if we want to
turn the car into a black hole then have to squash it into the size of a neutrino, which is pretty
small (about 1×10-24
m wide).
In order for an object to form a black hole it has to be compressed below a certain radius, this
radius is given by the equation- Rsch = 2GM / C2
Fig 2: Showing Schwarzschild radius
This radius is known as the Schwarzschild radius, after physicist Karl Schwarzschild who
discovered this equation in 1916.
WHY IS IT CALLED A HOLE?
Albert Einstein’s General Theory of Relativity in 1915 deals largely with the effects of gravity,
and predicts the existence of black holes and singularities. Einstein hypothesized that gravity is a
direct result of mass distorting the space. He argued that space behaves like an invisible thing
having elastic property. Celestial bodies interact with this space-time and create depressions
what is termed as ‘gravity wells’ or ‘gravity holes’ and draw nearby objects into their orbits.

39
In a galaxy of many stars, the black hole lies at the centre of it. So the centre of the galaxy
appears as black like a hole in the universe.
CAN A BLACK HOLE SUCK US IN?
Actually a black hole is not like a vacuum, sucking in everything around it - though it is often
thought by many people. A black hole’s gravity pull is so strong that everything passing close to
it is affected by its strong gravitational attraction. Astronomers think that because of this very
strong gravity, strange things may happen near black holes. Some of them believe that time
slows down, and space becomes infinitely warped near black hole. The laws of physics would
cease to exist. Now the most important question is that how likely a black hole could enter our
solar system? Well, it has definite possibility though it is very small. In fact the chance of a black
hole swallowed our planet is estimated at one in a trillion.
WHAT HAPPENS IF WE FALL INTO A BLACK HOLE?
If we all fall into a black hole, surely all of us were doomed. Once someone fall into a black hole
then he can never get back out from it, but it is true that we will probably be dead before we get
there. The gravity we feel from any object gets stronger as we become closer to it. As we
approach a black hole, the force of gravity on our feet can be thousands of times stronger than
the force on our head! This has the effect of stretching, pulling ours apart like taffy. Scientists
call this “spaghettification” (vertical stretching and horizontal compression of objects into long
thin shapes like spaghetti ). By the time we reach a black hole, we will be a thin stream of matter
many miles long. It probably would not hurt though, even falling from thousands of miles away
from a black hole. The entire episode will be over in a few milliseconds.
Some black holes greedily take over matter, stealing it from an orbit of a companion star as in
the case of super-massive black holes, from surrounding gas clouds. As the matter falls in, it
gathers these into a disk just outside the hole. As the piled up matter rotate at huge speeds, the

40
matter in this accretion disk gets extremely hot—even reaching millions of degrees. It will emit
radiation, in particular high-energy X-rays in case of black hole.
Fig 3: Showing the inner zone of the accretion disk of a stellar-mass black hole
Long before the black hole could suck us, we would be probably get fried by the light. But
suppose we somehow manage to survive the trip into black hole. Then what strange things await
for us on our journey forever? Once we pass the point where the escape velocity is faster than the
light, then we can’t get out. This region is called the event horizon. That is because no
information from inside can escape and reach to us, so any event inside it is forever beyond our
horizon.
If the black hole is rotating, different chaos may be waiting for us. It is like a maelstrom (very
powerful whirlpool or a large, swirling body of water) crashing into us like water churning at the
bottom of a waterfall. At the very core of the black hole, all the matter finally collapse and all the
way down to a point. It is like that the matter has disappeared from the universe, but its mass is
still exists there. At the singularity, space and time come to an end.
IF THEY ARE BLACK, THEN HOW CAN WE FIND THEM?
The black hole itself may be invisible, but its gravity does not. Gravity leaves the fingerprints of
it. In spite of its invisible interior, the presence of a black hole can be traced through its
interaction with other matter and with electromagnetic radiation. Astrophysicists searching for

41
black holes thus have to depend on indirect observations. The existence of a black hole can
sometimes be identified by observing its gravitational interactions with its surroundings.
Some stars form in pairs, called binary systems, where the stars revolving each other. Even if one
of them becomes a black hole, they may remain in revolving each other. By carefully observing
such a system, astronomers can measure the radius of the orbit of the normal star and determine
the mass of the black hole. Fortunately, astronomers have discovered an extremely important
thing to trace the black holes. It is X-rays. If a black hole is swallowing matter from a companion
star, then the matter becomes very hot and emits X-rays. This is like a signature of a black hole.
That is why astronomers want to make spacecraft equipped with special detectors that can trace
X-rays. In fact, black holes emits so much X-rays that many thousands of black holes can be
spotted by this method. EXIST (Energetic X-ray Imaging Survey Telescope) is one such
spacecraft which is able to detect tens of thousands of black holes, some of them may be many
many (billions) of light years away from us. EXIST will create full-sky map for locating black
holes, including those which may be hidden by gas and dust.
OBSERVATIONAL EVIDENCE
Actually, black holes are everywhere! According to astronomers, there are probably millions of
black holes in our Milky Way Galaxy alone. It is now explicitly accepted that the near the center
of every galaxy a super-massive black hole exists. This may seems a lot, but the nearest one
discovered is still 1600 light years away from us- a huge distance apart. This is certainly too far
away to affect us anyway. A giant black hole in the center of the galaxy is even further away-
30,000 light years away from the earth. We are in no danger of being sucked in. For a black hole
to be dangerous for us, it is to be very close, probably less than a light year away.
The black hole, Cygnus X-1, was first discovered by Charles Thomas Bolton, Louise Webster
and Paul Murdin in 1972. Some of the most notable galaxies with super-massive black hole
candidates include the Andromeda Galaxy, M32, M87, NGC 3115, NGC 3377, NGC 4258, NGC
4889, NGC 1277, OJ 287 and the Sombrero Galaxy.
CONCLUSION
Considering all the previous discussions, it can be argued that the black holes are like celestial
monster in the universe. Black hole could be a serious concern for the mankind to survive in this

42
beautiful earth though the probability of occurrence of an incident that we all are sucked by the
black hole is very small. So there is no need to fear too much for getting spaghettified soon.
Now-a day, many scientists are working in this field. Many scientists have given their opinion
and explanations about the black hole. But these views are different. This is creating an uncertain
situation to be known explicitly about the black hole. There is no independent concrete theory or
assumption to interpret this phenomenon-black hole. These researches can be very useful for all
of ours for fighting against this astronomical monster.
But still there are lots to discover or investigate about the black holes. Many quality researches
on black hole are to be continued to find out many interesting things about black hole. Falling
into a black hole would be the last thing that we ever can do, but for the scientists, black holes
are just the beginning step of our explorations in space, time, and everything in between.
BIBLIOGRAPHY
1. Arkani–Hamed, N., Dimopoulos, S., Dvali, G. (1998). "The hierarchy problem and new
dimensions at a millimeter". Physics Letters B 429 (3–4): 263.
2. Bozza, V. (2010). "Gravitational Lensing by Black Holes". General Relativity and
Gravitation 42 (42): 2269–2300.
3. Cattaneo, A. & Bernardi, M. (2003). The quasar epoch and the stellar ages of early-type
galaxies. Mon. Not. R. Astron. Soc. 344, 45–52.
4. Davies, P. C. W. (1978). "Thermodynamics of Black Holes". Reports on Progress in
Physics 41 (8): 1313–1355.
5. Detweiler, S. (1981). "Resource letter BH-1: Black holes". American Journal of Physics
49 (5): 394–400.
6. Droste, J. (1917). "On the field of a single centre in Einstein's theory of gravitation, and
the motion of a particle in that field". Proceedings Royal Academy Amsterdam 19 (1):
197–215.
7. Droz, S., Israel, W., Morsink, S. M. (1996). "Black holes: the inside story". Physics
World 9 (1): 34–37.
8. Ferrarese, L. & Merritt, D. (2000). A fundamental relation between supermassive black
holes and their host galaxies. Astrophys. J. 539, 9–12.

43
9. Ghez, A. M., Klein, B. L., Morris, M. et al. (1998). "High Proper-Motion Stars in the
Vicinity of Sagittarius A*: Evidence for a Supermassive Black Hole at the Center of Our
Galaxy". The Astrophysical Journal 509 (2): 678.
10. Gillispie, C. C. (2000). Pierre-Simon Laplace, 1749–1827: a life in exact science.
Princeton paperbacks. Princeton University Press. p. 175.
11. Hawking, S. W. "Does God Play Dice?".www.hawking.org.uk. Retrieved 2009-03-14.
12. Hawking, S. W., Penrose, R. (1970). "The Singularities of Gravitational Collapse and
Cosmology". Proceedings of the Royal Society A 314 (1519).
13. Hawking, S. W. (1971). "Gravitational Radiation from Colliding Black Holes". Physical
Review Letters 26 (21): 1344–1346.
14. Israel, W. (1989). "Dark stars: the evolution of an idea". In Hawking, S. W., Israel, W.
300 Years of Gravitation. Cambridge University Press.
15. Kormendy, J., Richstone, D. (1995). "Inward Bound—The Search For Supermassive
Black Holes In Galactic Nuclei". Annual Reviews of Astronomy and Astrophysics 33 (1):
581–624.
16. Kovacs, Z., Cheng, K. S., Harko, T. (2009). "Can stellar mass black holes be quark
stars?”. Monthly Notices of the Royal Astronomical Society 400 (3): 1632–1642.
17. Krolik, J. H. (1999). Active Galactic Nuclei: From the Central Black Hole to the Galactic
Environment. Princeton Univ. Press.
18. Lewis, G. F., Kwan, J. (2007). "No Way Back: Maximizing Survival Time Below the
Schwarzschild Event Horizon". Publications of the Astronomical Society of Australia 24
(2): 46–52.
19. Poisson, E., Israel, W. (1990). "Internal structure of black holes". Physical Review D 41
(6): 1796.
20. Skenderis, K., Taylor, M. (2008). "The fuzzball proposal for black holes". Physics
Reports 467 (4–5): 117.

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A REVIEW ARTICLE ON BLACK HOLE A MYSTERY IN THE UNIVERSE