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------------ 1881 - Supernovae are like snowflakes.
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- Astronomers use supernovae explosions as “ standard candles” and use the brightness to calculate the distance to the source. This calculation works only if the brightness is really predictable and the space travel is clear of dust. The brightness gets spread, gets dimmer, over the area of the expanding sphere. Area of a sphere is 4*pi*r^2
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--------------------- The measured brightness = 1.0 *10^-12 watts / meter^2
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--------------------- The assumed Luminosity = 3.8 * 10^36 watts
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---------------------- Brightness = Luminosity / 4*pi*(distance)^2
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----------------------- Distance^2 = Luminosity / 4*pi* ( brightness measured)
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--------------------- Distance ^2 = 3.8*10^36 / 4*pi* 10^-12 meters^2
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----------------------- d^2 = 0.3*10^48 meters^2
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----------------------- d = 0.55*10^24 meters
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------------------------ one light year = 9.5 *10^16 meters
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----------------------- d = 5.8 *10^6 lightyears
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- The distance to the supernovae source is 5.8 million lightyears.
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- There is another standard candle that is used in these distance calculations. Called a “Cepheid Variable” star. This is a young star that pulses at regular intervals. The pulse rate can be used to estimate the brightness, or Luminosity. However, these stars are too dim to be seen in far away galaxies. But, they can be used to calculate distances to a near galaxy, and a supernova in that galaxy and be used to develop a light curve of a supernova explosion at a known distance. And, that can be used for calculating distances to far away galaxies.
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- Supernovae have enormous brightness and can be seen in the farthest galaxies. A particular type of supernova , known a Type 1a, have a unique brightness curve (brightness amplitude versus time) and emit the same amount of light each time.
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- Astronomers theorize that this uniform explosion occurs when a White-Dwarf star is feeding off a companion until it triggers a thermo-nuclear explosion at exactly 1.4 times Solar Mass. ( See reviews listed at the end to get the explanation as to why this occurs, called the “ Chandrasekhar Limit”.)
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- However, new data indicates that this type explosion may be also caused by the merger of two White Dwarf stars. The luminosity may be greater under this other scenario. The light we see from these explosions is the result of radioactive decay. Certain isotopes like Nickel-56 decay into Coblalt-56 and then into the more stable iron isotope, Fe-56.
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- Supernovae explosions reach a peak brightness in a few days then decay in brightness to a sharp reduction in 500 days.
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- Recently Supernova SN2012cg was discovered that did not follow this pattern. It somehow continued to shine brighter. One possible explanation is that astronomers are seeing a light echo. Light is bouncing off a large dust cloud so we are seeing the brightness twice.
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- A second explanation is that the explosion produces heavier isotope, Colbalt-57, which takes longer to decay to Cobalt-56. This process could provide extra energy to the explosion. Thus an un- standard candle needs to be used carefully in calculating distances.
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- Astronomers need answers to these theories if distance calculations are to be accurate. They are intently studying the chemical composition of supernovae, especially those close to Earth that have known distance measurements.
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- Supernova SN2012cg is roughly 50 million lightyears away. When the brightness abruptly decays after 500 days it is believed to occur at the half life of the Nickel isotope,
Ni-56, when it transitions into the stable iron isotope, Fe-56.
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- To get distance measurements we are studying a particular type of supernova. However, in general, observing all other types of supernovae we begin to realize they are like snow flakes, no two are alike. On average, there is one supernova explosion in the Observable Universe per day.
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- The first supernova documented occurred A.D. 1006 by Chinese observers, we can call them naked eye astronomers. Then, Tycho Brahe recorded a supernova in 1572. Johannes Kepler recorded another in 1602. Today astronomers are using robotic, high resolution digital cameras, then , computerized image processing and pattern recognition covering large swaths of the night sky. Now, we are discovering thousands of supernovae every year.
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- Supernovae can shine brighter than a billion suns. Some are 100 times brighter and others 100 times dimmer than average. Some shine in the infrared and others in the ultraviolet. Some shine for years others only for a few days. Understanding the physics going on with all of this variety is challenging.
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- The Big Bang created hydrogen and helium, everything else in the Periodic Table of Elements was created in supernovae explosions. These dying stars created the elements that make up our world. The theory is that different varieties of supernovae created different squares of elements found in the Periodic Table.
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- The most common supernovae is a star that is 10 times the mass of the Sun and that have lifetimes of millions of years. Our Sun of one Solar Mass has a lifetime of 10 billion years. The 10 Solar Mass star fuses heavier elements until it reaches the element iron where fusion processes must stop. Gravity collapses the star once fusion radiation pressure quits. It looses 1 million fold in volume becoming a Neutron Star that is only 3 miles in diameter. The energy released blows the rest of the star and the many elements into space.
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- The total energy of the Sun that is burning for 10 billion years is released in a few seconds. The Neutron star at the core reaches 5 billion degrees F. The blast wave travels into space at 20 million miles per hour, 3% the speed of light.
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- The above description is a theoretical “ average” of a wide variety of supernovae explosions. Those that are 100 times brighter than average need a different explanation. Here are some of the theories of how these enormous energies could be attained.
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---------------------- Stars that are unusually large 150 to 250 Solar Mass. The cores under the enormous gravity get so hot to produce matter-anti-matter particle pairs. The sudden energy release would collapse and explode the star “ completely”.
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---------------------- Stars 70 to 150 Solar Mass may collapse, rebound, halt the nuclear reaction for a time, then re-expand and go through several of these cycles expelling debris out in shells. Later explosions could smash into these shells creating extremely bright supernovae.
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---------------------- Another theory does not require extremely massive stars. Maybe 10 Solar Mass with a Neutron star rotating to extreme speeds, 1,000 rotations per second. This could create an immense magnetic field. The spin energy could cause the debris cloud to shine a million times brighter. This event is called a “ Magnetar”.
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- At the opposite end of the supernovae spectrum there are some theories of how these supernovae could be 100 times dimmer than average:
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---------------------- Stars that are 300 to 1,000 Solar mass. You might expect these supernovae would be the biggest and brightest , but, the opposite could happen. The gravity could be so immense that the collapse becomes a Blackhole and much of the explosion disappears from sight. The supernova seen is from the halo of hydrogen gas that heats up and blows away.
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---------------------- Another creation of a Blackhole may come from the collision of two Neutron stars. The pair spiral into each other as their orbit decays due the emission of gravitational waves. 1% of the merger gets transmitted into space, 99% gets sucked into a Blackhole. The 1% debris could contain the heaviest elements like gold, platinum, and mercury, radioactive uranium and thorium. The glow of the debris field would be 100 times dimmer than the average supernova.
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- The gold on your finger may have this history. The supernovae debris cloud traveling 60 million miles per hour over 1,000 lightyears eventually settling into the curst of the planet Earth. It could happen. Stay tuned, an announcement will be made shortly.
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- Request these Reviews to learn more:
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- #1699 - Betelgeuse is 640 lightyears away. It is a 20 Solar Mass Red Supergiant star that could go supernova tomorrow.
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- #1698 - For every 1 million miles of space galaxies are receding each other by 47,000 miles per hour.
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- #1684 - What does a supernova explosion sound like?
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- #1566 - Supernovae are what we are made of. Gamma Ray bursts occur about once a day in the Observable Universe.
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- #1411 - The brightness also depends on the proportion m-of metals in the star.
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- #1320 - Supernova SN1006.
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- #1308 - Supernova Tycho Brahe of 1572
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- #831 - Supernova 1987A
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- #579 - Exploding stars create life, destroy life.
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--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
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- to: ------- jamesdetrick@comcast.net ------ “Jim Detrick” -----------
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----- 707-536-3272 ---------------- Monday, June 6, 2016 -----
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