- 1699 - Supernovae, Close to Home? This review explores the possibility of a supernova occurring in our Milky Way Galaxy in our lifetimes. What can we expect?
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--------------------------- 1699 - Supernovae, Close to Home?
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- Our Sun is too small to ever go “ supernova”. I will die a slow death over the next 5,000,000,000 years as it burns away its hydrogen and helium fuel. It will end up a beautiful planetary nebula with a White Dwarf Star left behind.
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- The White Dwarf will still be hot, but, it will have exhausted all its hydrogen and helium fuel. The nuclear furnace at its core will shut off and the cool down period will begin. It will last for eons.
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- Our Sun does not seem small to us. It is burning 600,00,000 tons of hydrogen every second. That nuclear reaction produces 596,000,000 tons of helium every second. The remaining 4,000,000 tons transforms into pure energy according to E = m*c^2.
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- At the core the energy starts out as high energy Gamma Rays, but, by the time it reaches the surface of the Sun , which takes 40,000 years scattering off the dense atoms. It looses energy and exit’s the surface as green sunlight.
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-------------------- Energy = mass * (speed of light )^2
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- We see this energy in the form of sunshine. The energy that powers all life on Earth.
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- Most of the stars in the night sky will behave in the same way. There are some more massive stars where their lifetime process becomes much different.
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- The truly large stars 6 time to 20 times the mass of our Sun will not go quietly. Once their nuclear fuel is extinguished their enormous gravity will cause an implosion to the center, then an explosion , into interstellar space. The explosion is called a “ supernova”.
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- One our two supernova will explode in our Milky Way Galaxy every century. The luminosity of each of these explosions will be 10 billion times greater than that of our Sun. One supernova is equivalent to a galaxy’s luminosity with 10 billion stars. What is left behind is not a White Dwarf star but a Neutron Star, possible a Blackhole.
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- We catalogued the first Supernova recording in 1680, known as Cassiopeia A.
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- The next supernova recorded occurred in 1860 in Sagittarius.
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- The most recent supernova close by in a neighboring galaxy, The Large Megellanic Cloud, was Supernova 1987A.
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- Remember, a supernova explosion occurs every one or two seconds somewhere in the Observable Universe. But, one or two per 100 years in our own Galaxy. This list of 5 massive stars in our galactic vicinity are the next likely candidates to go supernova. We could see these explosions with the naked eye. Google these stars to get a detailed description:
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----------------------- JK Pegasi
---------------------- Spica
---------------------- Betelgeuse
--------------------- Rigel
---------------------- Gamma Velorium - A Wolf-Rayet star
--------------------- RS Ophiuchi - A Red Giant and White Dwarf pair.
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- JK Pegasi is the closest. It is 1.7 Solar Mass with a binary companion White Dwarf star at 1.2 Solar Mass.
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- Some 260 lightyears away is Spica in the Constellation Virgo. It is a 10 Solar Mass star. Every star seems to have a different scenario for life expectancy. A 10 Solar Mass star will fuse helium into carbon and oxygen. More massive stars greater than 10 Solar Mass will fuse helium into carbon, then neon, oxygen, silicon, iron, nickel. Spica could become this type supernova.
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- Betelgeuse is 640 lightyears away. It is a 20 Solar Mass Red Supergiant star. It could go supernova in 20,000 to 100,000 years from now, or maybe tomorrow.
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- Gamma-Velorium, a Wolf-Rayet star will be a special supernova because it is 30 Solar Mass. It is 1,100 lightyears away.
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- When we get into the astronomical details we begin to realize each star is different. That in and of itself should tell us how unique we are. Each star is different but here is a general scenario of a star going supernova:
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- A massive star has so much gravity that it collapse all the element’s protons into the nuclei until the heaviest element is created, iron. Iron stops the process because it can not add anymore protons unless it adds energy. Up to iron adding protons, fusion, releases energy. It is that outward energy that keeps the star from collapsing. When the gravity gets so intense the electrons orbiting the iron collapse into the protons residing in the nucleus and become neutrons, releasing an explosion of neutrinos in the process.
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- When the star’s core collapses in this manner it reaches the center and bounces releasing an enormous amount of energy. Up to 100 times more energy than the Sun will release over its entire 10 billion year lifetime. The ball of neutrons left behind is a Neutron Star. The explosion that creates and splatters elements into interstellar space is a supernova. The shockwave causing this is traveling 22,000,000 miles per hour slamming into the outer layers of the massive star.
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- The scattering debris of the supernovae carry all the variety of elements in the periodic table throughout the Universe. We are still learning exactly how stars explode. In many ways they are all different , like snowflakes. Stay tuned, the next one in the Milky way could happen in your lifetime. Now, when it happens you will know what it is.
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- Picture is the Crab Nebula . It is a supernova that exploded 7,500 years ago. But, it is 6,500 lightyears away. So the image we see is only 1,000 years after it exploded. Already the shockwave is 6 lightyears in diameter. We are looking into the past.
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RSVP, with comments, suggestions, corrections. Index of reviews available ---
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