Connections Through Time, Issue 16:
July - September 2002
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| Our Milky Way galaxy's core reveals a star-forming region as recorded at several wavelengths invisible to the eye. Red indicates radio-wave emission, green indicates radiation in the mid-infrared, and blue is X-ray emission. The arrow indicates the super massive black hole at our galaxy's center. |
Black holes (BH) are rather common in the universe. Our Milky Way galaxy has a massive one at it's center with a mass of about 2.6 million times the mass of our sun. BHs have the unique property of being so massive and dense that near their center (inside a spherical surface called the event horizon) light cannot shine outward, hence the name 'Black Hole'.
Our galaxy's massive BH is called Sagittarius A*, or Sgr A*, and is in the direction of the constellation Sagittarius about 25,000 light years away. Sgr A* was first identified as a source of radio-frequency waves. However as it was investigated further with other frequencies of energy, it became clear that the core of our galaxy, as well as the core of other galaxies, are very dynamic places containing massive BHs at their centers.
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Galaxy NGC 1232, seen face on, is thought to look much like our Milky Way. New stars continue to form along outer fringes of the spiral arms. |
Stars and black holes first formed after the Big
Bang primarily due to
gravitational attractions between the elementary particles (photons-light,
electrons, positrons, neutrinos, and quarks) present at that time.
Additional BHs formed when stars with masses of about 10 or more times our sun's mass ran out
of nuclear fuel. Once the fuel is exhausted, gravity compresses the
remaining star mass to incredibly high densities. The process of
compression can cause a shock wave to form in the center of the star which then
propagates outward causing a supernova explosion
sending light/mass particles, including neutrinos, outward and leaving a remnant mass behind which
can become a BH. This process created the elements with higher atomic
numbers than iron,
including carbon and oxygen molecules essential to life - we truly are made of
"star stuff".
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Shown in this Hubble Space Telescope image are the famous rings of supernova 1987A in the Large Magellanic Cloud. This famous core collapse supernovae has provided vast quantities of data which has helped to discern supernova models. The first terrestrial detection of supernova neutrinos occurred with this supernova, which confirmed the basic neutrino heating paradigm for powering these catastrophic events. |
Black Holes attract mass due to their large gravitational pull. Sometimes the effects of mass being rapidly added to a BH can be quite spectacular. For example, an explosion millions of years ago
has left a galactic imprint. Centaurus A, which is "only" 11 million light-years away from us, is shown at the right. The composite image reveals signatures of the explosion including 2 arcs of hot gas at millions of degrees and a dust ring that extends 25,000 light-years in diameter. Perpendicular to the arcs, two jets shoot out high-energy particles, powered by an unseen super massive black hole in the galactic center, according to Chandra Observatory astronomers. The colors represent different energy wavelengths from several space and ground telescopes.Considerable controversy exists, however, over the timing of the galactic explosion - 10 versus 100 million years ago depending on the hypothesis for the nature of the explosion. We simply don't know the exact cause of the explosion. One hypothesis is that Centaurus A gobbled up another galaxy and increased the size of its central black hole.
Galactic mergers also unleash enormous amounts of energy into space and disperse particles that are used as building blocks to create future generations of stars.Now before you begin to think that all BHs are large, some serious scientists are planning experiments to create micro BHs. Gravity is still the key, however string theory and its higher dimensional approach (10+ dimensions) permits gravity to theoretically become much stronger for masses interacting at sub-millimeter sizes. At the high energies becoming available in the Large Hadron Collider at CERN in Geneva, subatomic particles could be smashed into each other and compressed so severely that their gravity could conceivable form and suck them into a black hole. Similar work is planned at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory.
There was some concern about these micro BHs getting out of hand and gobbling up all of Earth...not to worry. The small BHs, according to this theory, have been forming from cosmic radiation impacts on the atmosphere for a long time, and we are still here to debate the issue (see here). Gobbling does not occur because micro BHs "evaporate" very quickly into a multitude of measurable particles. One important reason for doing the micro BH experiments is to confirm or invalidate the current string theory formulations which attempt to unify the theories of quantum mechanics and general relativity.
And finally, other scientists are working on a desktop black hole which does not simulate the strong gravity in BHs, but does "bring light to a halt" at least for a short time. These simulations may shed
References
The Milky Way: A Tourist's Guide
The Black Hole in the Galactic Center
Black Holes Formed in the Beginning of the Universe: Could they be the Dark Matter?
Core Collapse Supernova Simulations in Multidimensions with Boltzmann Neutrino Transport
The Care and Feeding of Black Holes, or, How Can You See Something that Swallows Light?
Desktop Black Hole Possibly on the Horizon
Go to another section of
this
issue:
Intuition: Local Sidereal Time,
Intuition and Sagittarius A* Applications:
Associative Remote Viewing Presentation at the IRVA Conference
