Savannah Herdegen
Physics 1010
The Mystery of the Darkness
By Savannah Herdegen
PHYS 1010 T Th 8:30-10
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Savannah Herdegen
Physics 1010
Black holes have long been the subject of curiosity among physicists and
astronomers. They are inherently difficult to study, as even light cannot escape their
gravity. Many theories, with varying likelihoods, have been offered (often popularized or
even made up by science-fiction writers) to explain or give purpose to black holes.
However, some theories seem to be more likely than others and have allowed scientists
to conjecture the nature of these dark spots in space.
When our sun runs out of hydrogen to burn through at its core, it will die. It will
continue burning hydrogen in a shell around its core as its atmosphere stretches out far
enough to burn up Earth, turning it into a red giant. The core, meanwhile, will become
subjected to gravity it had previously resisted (because of the heat of the hydrogen
reactions) and it will become increasingly denser until it creates carbon through helium
reactions. After 100 million years of these reactions, the Sun’s atmosphere will have
continued to expand to the point that it reaches Jupiter and is considered a supergiant.
Only tens of thousands of years after that, most of the Sun’s mass will be lost and it will
become a planetary nebula – a hot core surrounded by stellar gases. The carbon core
will eventually cool and the gases dissipate and our Sun will become a white dwarf. 1
The deaths of stars with at least ten times more mass than our Sun are slightly
different. They continue to burn and condense after their core becomes carbon to create
oxygen, neon, silicon, sulfur, then iron. Then the star explodes. For a month, the dying
star becomes a bright supernova and emits its elements into space. If the core of the
supernova is about ten times that of our sun, it will cool to become a neutron star. If the
core is too massive to simply be a neutron star, it will collapse to become a black hole.1
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Savannah Herdegen
Physics 1010
If the core of the star rotated throughout its death, it will continue to rotate as a black
hole as well.2
The history of black holes in Western science stretches back almost a century. In
1916, Einstein published his general theory of relativity, which postulated that black
holes could exist. In the 1960s, John Wheeler coined the term “black hole,”3 and in
1970, Cygnus X-1 was named the first discovered black hole.4 The study of the nature
of Cygnus X-1 was spurred by “a friendly wager” between Stephen Hawking and Kip
Thorne (both prominent physicists), on whether or not it was actually a black hole.
Hawking said it was not a black hole and Thorne believed it was. It took almost twenty
years, but finally, the latter was proved correct.
Cygnus X-1 is a stellar black hole5 – the smallest size of black holes. They are
thought to be created when smaller stars up to three times the mass of our Sun collapse
on themselves. This collapse condenses all that mass into a small area, such as the
size of a city. As space debris flies by, it is sucked into the black hole, adding to its
density.3
“Supermassive black hole” is a well-known term (as shown by its use in pop
culture6) and the name justly describes the space anomaly. These holes have the
density of up to billions times that of our Sun, though they are only the size of our solar
system’s closest star. While there is no sure theory for how these supermassive black
holes are created, it is possible that they are the result of several stellar black holes
merging together.3
The smallest category of black holes are those called intermediate. These are a
relatively recent discovery. Previously, it was thought that black holes only come in
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Savannah Herdegen
Physics 1010
small and large sizes. Scientists postulate that these intermediate black holes may be
the result of close stars collapsing in a chain reaction. If several intermediate black
holes were to collide, it may result in a supermassive black hole. 3
Physics tells us that there is a relationship between mass, density, and gravity.
This means that objects with such a large density and such a small mass have
incredibly strong gravitational forces. In black holes, the gravity is so strong, the escape
velocity is greater than the speed of light. In other words, even light cannot escape the
power of black holes, which makes them practically invisible to astronomers. 3
However, in the past forty years, scientists have been able to study Cygnus X-1
long enough to conjecture what we would see if we could get closer to it. Cygnus X-1 is
situated near a blue star located about 6,070 light years away. Its gravitational force is
strong enough to pull matter from that star towards itself. Because black holes rotate,
the matter creates a disk around Cygnus X-1. The matter spins faster as it gets closer to
the black hole’s event horizon, where it will spin around 800 times per second, then
either be sucked into the black hole, or expelled away from it in a jet stream. Even after
millions of years, Cygnus X-1 has not had enough time to grow, so its current mass of
14.8 times that of our Sun, is probably close to its original mass.5
There are three layers to black holes – the outer event horizon, the inner event
horizon, and the singularity. The event horizon is the point of no return. Once a particle
crosses that line, there is no way for it to escape. This is because black holes do not
“suck” the space around it; rather, particles fall into the black hole. The singularity of a
black hole is where its mass is. Due to the physics of black holes, any object that falls
into it is stretched thinner and longer as it gets closer to the singularity.
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Savannah Herdegen
Physics 1010
In such a place as the vacuum of space, it is interesting to say that particles will
“fall” into a black hole. This relates back to how mass, density, and gravity affect each
other. According to Professor H. Demars, “mass tells spacetime how to curve; [the
curve in] spacetime tells mass how to move” (SLCC class lecture, 22 April 2014). The
more dense the mass, the deeper the curve it creates in the fabric of spacetime. The
deeper the curve, the more gravity it has on the matter around it. Just as a person
jumping falls back to Earth, a particle traveling near a black hole will fall toward the
center of its mass (its singularity).
Dark holes are a question scientists are still trying to answer. It has been shown
how dark holes form and how they interact with other matter. These insights have
further acted as evidence for the physics of space. Despite all that has been discovered
so far, however, there is still much to know about these dark spots in space.
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Savannah Herdegen
Physics 1010
The Life and Death of Stars (n.d.). Retrieved from
http://map.gsfc.nasa.gov/universe/rel_stars.html
Freudenrich, Craig. How Black Holes Work. (26 Nov 2006). Retrieved from
http://science.howstuffworks.com/dictionary/astronomy-terms/black-hole2.htm
Redd, Nola. Black Holes: Fact, Theory and Definition. (8 Feb 2013). Retrieved from
http://www.space.com/15421-black-holes-facts-formation-discovery-sdcmp.html
Is a Black Hole Really a Hole? Pathway To Discovery. (n.d.). Retrieved from
http://amazingspace.stsci.edu/resources/explorations/blackholes/lesson/whatisit/history.html
Anderson, Janet and Warzke, Megan. Cygnus X-1: A Stellar-Mass Black Hole. (17 Nov
2011). Retrieved from
http://www.nasa.gov/mission_pages/chandra/multimedia/cygnusx1.html
Black Holes and Revelations (n.d.). Retrieved from http://muse.mu/musicvideo/music/3.htm
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