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---------------------- 2300 - Supernova You Can See?
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- There are records in Chinese astronomy as far back as 70 A.D. but most were too ambiguous to say for certain they were all supernova. They could have been comets, or just nova. The Chinese records call them “ Guest Stars”.
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- In 185 A.D. there was a single entry by Chinese observers for the dazzling star in the constellation Centaurus. Other observations were also recorded in 369 and 386. Then in 393 A.D. a supernova was mentioned by the Chinese within the curve of the tail of Scorpius.
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- Then another observation in Chinese records in 837. These records were too ambiguous for astronomers today to say they were all supernova. It is fairly certain that at least two of them were definitely supernova explosions.
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- May 1, 1006 a supernova explosion appeared in the constellation Lupus the Wolf. It reached a peak apparent brightness of -7.5 magnitude (about 60% as bright as a full moon) and remained visible for two years.
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- Apparent brightness is the term used for the intensity of the light as seen from Earth. The brightness of any star is measured in magnitudes compared to the star Vega. Each increase in magnitude corresponds to a decrease in brightness by a factor or 100 ^ 1/5, or approximately 2.5 times.
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- An increase of 5 magnitudes corresponds to a decrease in brightness of 100 times. The star Vega has an apparent brightness of 0. However, its actual brightness is 62 times brighter that our Sun. It appears dimmer because it is 25.3 lightyears away. Brightness decreases at the rate of the square of the distance traveled.
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- So, each successive brighter magnitude is 2.5 times brighter than the preceding magnitude.
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---------------------------- Sirius ---------- - 1.44 magnitude
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--------------------------- Venus --------- - 4.4
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---------------------------- Full Moon ----- - 12.6
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---------------------------- Sun ---------- - 26.7
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Notice the negative numbers are brighter than Vega, positive numbers are dimmer. The Hubble Telescope can see stars as dim as +30. The limit of the naked eye is about +6.
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- Of course, it depends how far away the supernova is to determine actual brightness. In this case, even today, astronomers can use telescopes to see the remnants of this supernova.
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- Pictures taken in 1987 and again in 1998 show 11 years of expansion of hydrogen filaments that originated from this explosion. It’s behavior suggests that this supernova resulted from a binary system where a white dwarf star had an orbiting companion star.
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- The White Dwarf accretes gas from the companion star until the White Dwarf’s mass reaches 1.4 solar mass at which point it explodes as a supernova. (The 1.4 solar mass is known as the Chandrasekhar Limit. It is the mass at which gravity collapses the electrons to form helium nuclei before it goes supernova).
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- July 4, 1054, a premature Independence Day celebration explosion occurred in the constellation Taurus the Bull. It was noted in China by the astrologers in the Sung dynasty, and also in Japanese records. In the United States the Anasazi Indians documented a record of its appearance in a pictograph at Chaco Canyon, New Mexico.
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- The supernova reached a peak brightness of -3.5 magnitude Its brilliance exceeded that of Venus for many months and remained visible for over two years. It was a single massive star supernova, leaving a neutron star as a remnant, a pulsar spinning at 33 revolutions per second.
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- The supernova is visible today as the Crab Nebula in Taurus. Today it is 230 arc seconds across, a diameter of 38 trillion miles. It is still expanding at a rate of 1,400 kilometers / second (3 million miles per hour).
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----------------- The Crab Nebula is measured to be 230 arc seconds across.
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----------------- An arc second is defined = 206,265 * diameter in astronomical units / distance in parsecs.
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----------------- The distance to The Crab Nebula is 1,800 parsecs.
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----------------- The diameter of the Crab Nebula is 2 parsecs.
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----------------- A parsec is 19,175,700 million miles.
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----------------- One parsec is 206,265 astronomical units long.
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----------------- The tangent of one arc second = opposite side / adjacent side = 1 astronomical unit / 206,265 astronomical units.
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--------------------------- The diameter of the Crab Nebula is 2 parsecs
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--------------------------- The radius is 1 parsec = 3 * 10^13 kilometers
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--------------------------- Time = distance / velocity
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--------------------------- Time = 3*10^13 kilometers / 1,400 km / sec.
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-------------------------- Time = 2*10^10 seconds * 1 year / 3.16*10^7 seconds = 700 years. Or, 1300 A.D.
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--------------------------- The proper date is 1054 A.D. so this calculation is 250 years off.
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- August 6, 1181 in China and Japan records the supernova in the constellation Cassiopeia the Queen had a brightness of zero magnitude and was visible for six months. A few faint filaments of gaseous remnant can still be seen today using telescopes.
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- November 6, 1572 a supernova was recorded by Tycho Brahe in the constellation Cassiopeia the Queen, reached a peak brightness of -4 magnitude and was visible in daylight for two weeks and at night until March, 1574. ( Venus is -4.4 magnitude.)
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- Tycho’s observation occurred on the 11th during a walk before dinner, he notices a “directly overhead, a certain strange star … flashing its light with a radiant gleam. Amazed, and as if astonished and stupefied, I stood still, gazing … intently upon it and noticing the same star placed close to the stars which antiquity attributed to Cassiopeia.
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- When I had satisfied myself that no star of that kind had ever shone forth before, I was led into such perplexity by the unbelievably of the thing that I began to doubt the faith of my own eyes … And at length , having confirmed that my vision was not deceiving me, but in fact that an unusual star existed there … immediately I got ready my instrument.
I began to measure its situation and distance from the neighboring stars in Cassiopeia.”
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- Today the Chandra X-ray satellite has observed bipolar jets of silicon emitting from the giant remnant that is 20 lightyears in diameter. Studies conclude that the original star was 20 to 25 solar mass and that it detonated as a gamma-ray burster from a type-1A supernova.
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- Type 1A means that it was originally a binary star where the pair’s more massive star ages faster and eventually becomes a white dwarf. When the slower evolving companion star ages to the point when it swells in size, some of its matter spills into the white dwarf.
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- Hydrogen accumulates until the dwarf reaches a critical-mass threshold, called the Chandrasekhar limit, when it explodes as a titanic nuclear bomb. The companion star hurtles off into space like a stone thrown by a sling, retaining the velocity of its orbital motion.
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- Studies have found this companion star still racing at 304,000 mph, three times faster than other stars in the area. This find took seven years of searching. The star is 10,000 lightyears away, and is called Tycho G.
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- October 17, 1604, 400 years ago, a supernova in the constellation “Ophuichus the Serpent-bearer” was sited by Johannes Kepler. The explosion occurred on the 9th, but cloudy weather prevented Kepler from viewing it until the 17th.
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- Kepler carefully measured its position and tracked its changes in brightness for over a year. It had a peak brightness of -3 magnitude and faded from view in March,1606. The telescope was invented 3 years later in 1609.
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- Today Kepler’s supernova spans 14 lightyears, expanding at 4 million miles per hour. The Hubble Space Telescope, Chandra X-ray, and Spitzer Infrared Telescope have been studying the remnants and have set its distance at 13,000 lightyears.
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- February 27, 1987, what were you doing on that day? That night Oscar Duhalde was standing outside his telescope dome in Chile when he saw with the naked eye supernova SN1987A in the Large Megellanic Cloud, our neighboring galaxy.
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- It is difficult to see today because the nearby stars are 100 times brighter than the remnants that are left. It is still glowing because the explosion produced fresh elements and some are radioactive.
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- In particular, the decay of radioactive titanium continues to excite the debris and will continue glowing for decades. In addition to the debris, left behind is a neutron star spinning at 1968.629 revolutions per second.
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- SN1987A is the most studied supernova ever. It is 160,000 lightyears away and was bright enough to have been a 20 solar mass star. Astronomers are not positive which star went supernova but Sanduleak 69 202 is a star that was once there and since disappeared.
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- Only eight supernova have been observed with the naked eye over the last 1,000 years. Yet, it is estimated that in each galaxy there is a supernova explosion every 50 years. In our Milky Way galaxy most of these would be hidden from view due to distance and dust.
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- But, how many supernova can be seen using modern telescopes? Astronomers say that, on average one supernova explosion can be found each day coming from all directions in the sky.
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- Supernova are continuously enriching the interstellar medium with elements heavier than hydrogen and helium. The nearest remnants formed are only 300 lightyears away. These remnants are from the Gum Nebula that exploded 11,000 years ago in the constellation Vela. Its brilliance would have been as bright as a quarter Moon. Today the supernova remnant spans 60 degrees across the sky, a diameter of 2300 lightyears.
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- What would happen if we had a closer supernova explosion in our Milky Way? Say, if Betelgeuse in the Constellation Orion goes supernova today. It is 500 lightyears away. How would it affect us?
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- First the neutrinos would reach us. 99% of the energy of a supernova is carried away by neutrinos. Light and the expansion of the remnant are the remaining 1% of the energy. Light from the explosion would not reach us for 500 years. Or, put another way, if Betelgeuse exploded 500 years ago we would not know it until tomorrow.
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- The expanding shell from the supernova is traveling at 20,000,000 miles per hour. At that speed it would arrive here in about 100,000 years after the explosion. The shockwave would hit us with atomic and subatomic particles ten times the mass of the Sun. That amounts to 20,000 protons per second per square inch.
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- The Sun’s solar wind, by comparison, is about 50,000,000 protons per second per square inch. So, although it will be detectable, the “solar wind” from a Betelgeuse supernova probably won’t do much biological damage.
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- However, the Betelgeuse “ solar wind” will be traveling 20,000,000 miles per hour compared to our Sun’s solar wind that is traveling at 1,000,000 miles per hour. This increased amount of pressure would cause the Sun’s heliosphere to collapse from its present radius of 100 astronomical units to less than Earth’s orbit, one astronomical unit. Earth’s magnetosphere would be compressed.
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- The energy particles in the Van Allen belts around Earth would be amplified during this compression. We would be subjected to high energy x-ray radiation for the next 10,000 years. These x-rays would not reach the surface thanks to Earth’s protective atmosphere. However, it would limit space travel for astronauts who venture outside the space ship of our Mother Earth.
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- March 9, 2019 60
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