- Attachment: X- Ray of Crab Nebula
- The very first object that astronomers put in their Messier Catalog was “M1” for the Crab Nebula. Astronomers were tracking comets and “M1” was identified as not a comet. It did not move. Astronomers had to stare at a object for a long time to determine if it moved. These Messier identifications allowed them to skip some objects they saw. This one was in the Constellation Taurus the Bull just 6,500 lightyears away.
- On July 3, 1054 our time, it was a star. One day later, on July 4,1054, it was a supernova that became as bright as the planet Venus in the night sky. It was so bright it could even be seen during the day for several weeks.
- Ever since this supernova explosion occurred the gas and material have been expanding outwards at 1,000 miles per second ( 360,000 miles per hour). Today we see it as the Crab Nebula occupying the left horn of Taurus the Bull.
- The Crab is an especially bright nebula but the source of its brightness is not starlight, not reflected light, not excited gas, not extreme temperatures, not even nuclear fusion. Its unusual bright light is synchrotron radiation.
- Synchrotron radiation occurs when electrons are forced to change directions, or accelerate, in a powerful magnetic field. The Crab’s magnetic field is 1 trillion times more powerful than Earth’s. The powerful magnetic field sends electrons into giant spirals at enormous speeds. The electrons emit their energy in the form of an eerie blue light of radiation.
- What causes this powerful magnetic field?
- At the center of the Nebula is a Neutron Star called a Pulsar. The rotating Neutron Star sends out a beam of energy every rotation at 33 times per second. The is how fast the star is spinning. The mass of the Pulsar is about 1 Solar Mass. It is a remnant of the giant star left over at the center 958 years ago.
- The Neutron Star is a spinning dynamo that produces a powerful magnetic field. The magnetic field acts as a drag on the spin that is slowing the rate down. Today it is spinning at 33 rotations per second. In the year 4000 it will have slowed down to 17 rotations per second.
- The Neutron Star is extremely dense and only 16 miles in diameter. To visualize the density start with the largest cruse ship on the ocean and crunch it down to the size of the ball in a ballpoint pen.
- This thought may amaze you! But, realize that the nuclei of every atom in your body is this same density. The surface of the Crab Pulsar is a kind of lattice of this same atomic structure. One-half mile beneath the surface of this impenetrable crust is a liquid that is even denser than the surface. In this case the dense liquid core is rotating at a different spin rate then the surface. This is the dynamo that is creating the powerful magnetic field.
- The Crab Nebula is a beautiful sight to behold. Now you know its glow is synchrotron radiation. Amaze your friends as you point t the left horn of Taurus the Bull and relay the story.
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(1) Synchrotron radiation is the electromagnetic radiation emitted when a charged particle is rapidly accelerated. It occurs at ultra relativistic velocities near the speed of light. The magnetic field causes the charged particles to follow a curved path because the magnetic force is perpendicular to the direction of the particle’s travel. Changing direction is a form of acceleration. No acceleration would mean a constant speed in a straight line.
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