- On July 3, 1054 it was a star in the night sky.
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- On July 4, 1054 it was a supernova so bright it could be seen during the day and at night it was as bright as the planet Venus. The gas and material was exploding outward at 300,000 miles per hour.
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- Today we call it the Crab Nebula in the Constellation Taurus the Bull, 6,500 lightyears away.
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- Its brightness today is no longer an explosion, it is synchrotron radiation. The Neutron Star left behind has a spinning magnetic field that is sending electrons into giant spirals near light speed. When a charged particle travels at near light speed it emit’s a blue light of radiation.
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- The Neutron Star is rotating 33 times per second. It is 1.4 Solar Mass but only 16 miles in diameter. This means it is exceedingly dense.. The Star is 958 years old.
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- The expanding ball of gas and debris creates a bubble. Inside the bubble is a ring created by shockwaves of radiation blasting off the Neutron Star. A shockwave is a wave of energy expanding outward. It is a density wave, a sound wave. When its energy hits gas and dust it transfers energy accelerating the gas and dust, or heating it. Some of the energy is absorbed and re- emitted at a lower frequency. Ultraviolet energy is absorbed and infrared energy is emitted. Most of the energy is reflected. This is a “ light echo” and that is what lights up the ring. A light echo is just like a sound echo except it occurs at astronomical distances.
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- The Crab Nebula is dynamic and very unusual for astronomers to witness over their lifetime. Images taken over the past 50 years are compared and the expansion actually can be seen and measured over time. The angle in arc-seconds can be scaled to distances in lightyears.
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- The calculations for the size of the bubble can be found in Review # 1261.
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- This review will use the same methods to calculate the size of the ring. The ring is an ellipse. Draw a circle on a piece of paper and tilt it so it looks like the ellipse. On the image the ellipse is 10 millimeters diameter. The width of the image is 5 lightyears and70 millimeters across. The scale of the image is:
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---------------------------- 5 lightyears / 70 mm = 0.071 LY / mm
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---------------------------- The radius of the ring is 5 millimeters.
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-------------------------- The radius of the ring is 0.36 lightyears.
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------------------------- 1 lightyear = 5.9 * 10^9 kilometers.
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---------------------- The radius of the ring is 2.1*10^12 kilometers
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- The high energy particles are traveling at 95% the speed of light. The particles reach the ring in 85 days:
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------------------------ velocity = 0.95 * 300,000 km / sec = 285,000 km/sec
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---------------------- time = 2.1*10^12 km / 2.85^10^5 km / sec = 0.74*10^7 seconds
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----------------------- 1 day = 86,400 seconds
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------------------------time = 74*10^5 / 8.64*10^4 = 85 days
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- If the astronomers witnessed a burst of light from the ring it took 81 days for the light to reach the ring from the Neutron Star:
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----------------- time(light) = 2.1*10^12 / 3*10^5 / 8.64*10^4 = 81 days
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- Astronomers would have to wait 81 days to see how the light echo affected the ring and another 4 days to see how the particles affect the ring.
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- In the past several months astronomers have witnessed dynamic changes in the Crab using orbiting telescopes:
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--------------------- Fermi Gamma Ray telescope
--------------------- Chandra X-ray telescope
-------------------- Spitzer Infrared telescope.
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- On April 12 Gamma Ray flares were seen to have energies of 100 million electron volts, 30 times more energy then previous outbursts.
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- The reason for this sudden outburst of energy remains a mystery. Astronomers believe the flares occur as the intense magnetic field near the Pulsar Neutron Star undergoes sudden structural change, much like the sunspots and Solar Flares. Electrons get accelerated in the spinning magnetic field to nearly light speed. The high speed charged particle emit Gamma Rays. The energies observed are 100 times greater than our particle accelerators can achieve here on Earth.
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(1) Other Reviews that are available:
------------ #1334 Unusual light from the Crab Nebula
----------- #1261 What is making the Crab Nebula so active?
----------- #1100 , #862, #720 Crab Nebula
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RSVP, please reply with a number to rate this review: #1- learned something new. #2 - Didn’t read it. #3- very interesting. #4- Send another review #___ from the index. #5- Keep em coming. #6- I forwarded copies to some friends. #7- Don‘t send me these anymore! #8- I am forwarding you some questions? Index is available with email and with requested reviews at http://jdetrick.blogspot.com/ Please send feedback, corrections, or recommended improvements to: jamesdetrick@comcast.net. ---- “Jim Detrick” -- www.facebook.com, -- www.twitter.com, -- 707-536-3272 Monday, December 31, 2012
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