Catherine's Annotated Bibliography
Source 1: Black Holes, Wormholes, and Time Machines, Second Edition
Citation of Source 1:
Al-Khalili, J. (2012). Black Holes, Wormholes and Time Machines, Second Edition. Boca Raton, Florida: CRC Press.
Notes about Source 1:
Many people thought that French mathematician and astronomer Pierre Laplace was the first person to predict the existence of black holes in 1795. However, it was English geologist John Michell who presented the formation of black holes to the Royal Society of London in 1783. A famous American theoretical physicist, Kip Thorne, states "the law of modern physics virtually demand that black holes exist."
What is a black hole? A black hole is an object, which is infinitely small and dense and it has a gravitational field that is so strong, not even light can escape its surface. How is a black hole formed? When a star dies it, uses up all fuel in its core and can no longer carry out nuclear fusion, black holes form.
What is black hole's structure? The center of a black hole is the singularity, where all the mass is compressed to be the infinitely small speck. From the singularity to the surface of a black hole is the event horizon, also called the Schwarzschild radius. Within the Schwarzschild radius, nothing can escape the gravitational pull of the black hole, not even light. It is the point of no return. When an object goes beyond the Schwarzschild radius, it cannot escape the black hole’s gravitational pull. The accretion disk, which is stellar material spinning toward the center of the black hole, is outside the event horizon. When a black hole is rotating, there will be region called the ergosphere. It means a spinning black hole will have two horizons: the inner one is spherical, the original event horizon from which nothing can escape and the outer one is slightly bulged-out at the equator and marks the surface of the ergosphere. An object falls into the ergosphere can still escape, but nothing can stand still due to the strong dragging. For some black holes emitting powerful magnetic fields, there are jets of gas.
How do we know about the existence of black hole? Stellar binary systems, such as the x-ray binary system, support that black holes do exist. Steven Hawking admits that it detects a black hole called Cygnus X-1, about six light-year from Earth. Twenty five years ago, Steven Hawking found that a black holes leaks its energy, will shrink in size until nothing is left. This energy is now known as Hawking radiation. It may be possible to artificially capture the energy from black holes.
Source 2: British Broadcasting Corporation (BBC)
Citation of Source 2:
Ball, P. (2013, December 3). Could we harness power from black holes? Retrieved October 9, 2015, from http://www.bbc.com/future/story/20131203-could-black-holes-provide-energy
Notes about Source 2:
Black holes were once thought of as energy drains, where nothing could escape, rather than energy sources. But that view evolved when Stephen Hawking and others brought quantum physics into the subject. Hawking showed in the 1970s that black holes should emit energy from their boundaries in the form of radiation produced by quantum fluctuations of empty space. Eventually the black hole radiates itself away – it evaporates. However, the radiation is emitted very slowly. Is it possible to induce a black hole to release all its Hawking radiation sooner, so that in effect it becomes like a ball of fuel? It is not a mere speculation, for physicists have believed for at least 30 years that it might be possible. Over the years there were many suggestions from physicists on how to harness the Hawking radiation from black holes. In 1983, George Unruh and Robert Wald suggested a box and rope method as a radiation collector which works similarly to a bucket getting water from a well. For this to happen, a strong enough rope and winding mechanism is required to prevent the box from being swallowed by the black hole. Unruh and Wald estimated that in principle more energy can be extracted per second from a single black hole than is radiated from all the ordinary stars in the observable universe. In 1994, Albion Lawrence and Emil Martinec suggested another method called ‘dip strings’. The radiation would run up like oil up the wick of an oil lamp. This is thought to be slower than the box and rope method but research done by Adam Brown of Princeton Center of Theoretical Physics shows that the speed of both methods would be about the same rate. Due to the risks of the box and rope method’s possibility for malfunctioning, Brown believes the dip strings method would be a more realistic approach. He argues that the preferable way to draw the energy from black holes is to puncture the event horizon with lots of radiation-wicking strings, and let them drain it out of existence.
Source 3: Monthly Notices of the Royal Astronomical Society (MNRAS)
Citation of Source 3:
Blandford, R., & Znajek, R. (1977, September 1). Electromagnetic extraction of energy from Kerr black holes. Retrieved October 30, 2015, from http://mnras.oxfordjournals.org/content/179/3/433
Notes about Source 3:
The original publication of the Blandford–Znajek process which is a mechanism for the extraction of energy from rotating black holes. If a rotating black hole is threaded by magnetic field lines supported by external currents flowing in an equatorial disc, an electric potential difference will be induced. A surrounding force-free magnetosphere can be made if the magnetic field strength is large enough for the vacuum to be unstable in production of electron-positron pairs. Energy and angular momentum can be extracted electromagnetically under these circumstances. As a consequence it is shown that charge can never contribute significantly to the geometry of a rotating hole. Fundamental equations to describe stationary axisymmetric magnetosphere are derived and the details of the energy and angular momentum balance are discussed. A technique is developed which can be used to provide approximate solutions for slowly rotating holes. Their proposed model consists of an active nuclei containing a large black hole surrounded by a magnetized accretion disc. Within the model, electrons can accelerate at large distances from the black hole and will not be subject to major losses, a defect in existing models of the time. Based on observations of compact and extended radio sources, if the magnetic field lines are a paraboloidal shape the energy will beam along antiparallel directions. This process relies on magnetism.
Source 4: NASA's Jet Propulsion Laboratory (JPL)
Citation of Source 4:
Clavin, W. (2015, October 27). Black Hole Has Major Flare. Retrieved November 5, 2015, from http://www.jpl.nasa.gov/news/news.php?feature=4753
Notes about Source 4:
With new observations from NASA’s Explorer missions Swift and the Nuclear Spectroscopic Telescope Array, NuSTAR, black holes’ behaviours are better understood. The two space telescopes caught a supermassive black hole’s giant eruption of x-ray light, helping astronomers address the puzzle of how supermassive black holes flare. From the results, it is suggested that the black holes send out beams of x-rays when their surrounding coronas – sources of extremely energetic particles – launch away from the black holes. Dan Wilkins of Saint Mary’s University in Halifax, Canada, lead author for the paper that will appear in the Monthly Notices of the Royal Astronomical Society says, “This is the first time we have been able to link the launching of the corona to a flare. This will help us understand how supermassive black holes power some of the brightest objects in the universe.” Supermassive black holes are often encircled by large disks of hot, glowing material. They do not give off any light themselves. Swirling gas is pulled into the black hole with its gravity, heating the material and resulting in different types of light. The corona is another source of radiation near a black hole. Details about the coronas appearance and how they form are unclear. There are currently two likely configurations of coronas. The ‘lamppost’ model says they are compact sources of light, similar to light bulbs, that sit above and below the black hole, along its rotation axis. The other model proposes that the coronas are spread out more diffusely, either as a larger cloud around the black hole, or as a ‘sandwich’ that envelops the surrounding disk of material like slices of bread. It is possible that coronas switch between the lamppost and sandwich configurations.
Source 5: National Aeronautics and Space Administration (NASA)
Citation of Source 5:
Harrington, J., & Clavin, W. (2014, August 12). NASA's NuSTAR Sees Rare Blurring of Black Hole Light. Retrieved November 12, 2015, from http://www.nasa.gov/press/2014/august/nasas-nustar-sees-rare-blurring-of-black-hole-light/#.Vj-qG_mrTIU
Notes about Source 5:
NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) captured a rare event surrounding a supermassive black hole. The corona, a compact source of x-rays near the black hole, has moved closer to the black holes in a few days. "The corona recently collapsed in toward the black hole, with the result that the black hole's intense gravity pulled all the light down onto its surrounding disk, where material is spiraling inward," said Michael Parker of the Institute of Astronomy in Cambridge, United Kingdom. As the corona shifted closer to the black hole, the gravity of the black hole exerted a strong tug on the x-rays emitted resulting in extreme blurring and stretching of X-ray light. This is the first time the event has been observed to this degree and detail. Supermassive black holes are thought to reside in the centers of all galaxies. Some are more massive and rotate faster than others. The black hole in the study, referred to as Markarian 335, or Mrk 335, is about 324 million light-years from Earth in the direction of the Pegasus constellation. It is one of the most extreme of the systems for which the mass and spin rate have ever been measured. The black hole squeezes about 10 million times the mass of our sun into a region only 30 times the diameter of the sun, and it spins so rapidly that space and time are dragged around with it. Even though some light falls into a supermassive black hole never to be seen again, other high-energy light emanates from both the corona and the surrounding accretion disk of superheated material. Although astronomers are uncertain of the shape and temperature of coronas, they know that coronas contain particles that move close to the speed of light.
Source 6: American Physical Society (APS) Physics
Citation of Source 6:
Schirber, M. (2015, June 26). Focus: Energy Boost from Black Holes. Retrieved October 9, 2015, from https://physics.aps.org/articles/v8/60
Notes about Source 6:
In the last few decades, it is believed that a modest energy gain resulted from particle input to the black hole. Conventionally it is believed that black holes are only takers, not givers, but collisions among matter around a spinning black hole can result in high-energy particles that emerge with some of the black hole’s energy. Recently, there is a possibility of about an energy gain 10 times greater than conventional beliefs. Jeremy Schnittman of the NASA Goddard Space Flight Center in Greenbelt, Maryland theoretically experimented this idea with a computer program he created. Schnittman dropped dark matter particles into the black hole collider and yielded surprising results of greater gamma rays than the initial particle input. Prior the radiation is believed to be 1.3 times. Schnittman’s research indicates a radiation of 13 times more than the initial particle input. Previous work had assumed the initial particles collide when they reach their maximum speed – right as they fall into the event horizon. But then the escaping particle expends nearly all of its energy moving against gravity on its outward trip. “The black hole giveth, and the black hole taketh away,” Schnittman says. He redid the calculations, with the assumption that one of the initial particles swings, or sling shots, around the black hole and is actually on an outbound trajectory when it collides with the other particle. Although the collision energy is slightly less than it could be, the outward momentum of the sling-shotted particle causes one particle to emerge with more energy, as much as 13 times the initial combined energy. Although the occurrence is possible, Tomorohiro Harada from Tokyo University says that the possibility of the occurrence is slim. It can arise in situations with complex accretion disks and strong magnetic fields.
Source 7: National Broadcasting Company (NBC)
Citation of Source 7:
Than, K. (2006, April 24). Black holes generate ‘green’ energy. Retrieved November 5, 2015, from http://www.nbcnews.com/id/12465712/ns/technology_and_science-space/t/black-holes-generate-green-energy/
Notes about Source 7:
Matter that did not pass the point of no return can release energy in the form of diffuse light or focused jets of energy through friction and interaction with a black hole’s magnetic field. In the new study, nine supermassive black holes at the center of galaxies are observed. The black holes release 1 000 times more jets of energy than diffuse light. "If you could make a car engine that was as efficient as one of these black holes, you could get about a billion miles out of a gallon of gas," said Steve Allen, the study’s team leader, from the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University. "In anyone's book, that would be pretty green." Majority of the energy are radio wave emissions but at least one black hole released the energy in the form of x-rays. "The energy in these jets is absolutely huge, about a trillion trillion trillion watts," said Steven Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University. The finding provides potential implications for other types of black holes as well, including smaller, stellar-mass black holes for other researchers. "We already knew that powerful quasars are very efficient at making light. Now we know that black holes in elliptical galaxies are efficient as well," said Kim Weaver, a researcher at NASA's Goddard Space Flight Center who was not involved in the study. "This suggests that being green is a trait that all black holes may have in common." Scientists think the supermassive black holes are green in another way, too. The energy that each black hole emits as jets warms the surrounding environment. This prevents gas from cooling and coalescing into billions of new stars, and places an upper limit on how large a galaxy can grow.