Messier 1, The Crab Nebula
The Crab Nebula or M1 is what remains of an ancient supernova and is one of the first pulsars ever identified. It lies in the direction of the constellation Taurus and is the first object ever associated with an historical supernova. While it was discovered by English astronomer John Bevis in 1731, it wasn’t until the early 20th century that astronomers discovered that it seemed to be expanding, indicating a relatively recent supernova. In fact, on July 4th, in the year 1054, Chinese astronomers recorded a new star in the same part of the sky as the Crab Nebula. That new star was bright enough to be seen during the day. A sudden new “star” recorded in ancient history, usually means either a comet or a nova. In fact, the word “nova” means “new star”. Nova happen whenever an old star suddenly brightens as it throws off material into space, often a result of collecting this material over time from a nearby younger star. A nova does not usually destroy the star.
    A supernova, however, occurs when a star reaches the end of its life and explodes in one of the most violent events in the universe. A supernova’s progenitor star is then greatly changed and often destroyed in the process. Most supernova then become a neutron star or if massive enough, a black hole. A neutron star is a gigantic atomic nucleus, tens of kilometers across. It is held together by gravity and so dense that it contains only neutrons with protons and electrons combining during the supernova in extreme gravity and explosive conditions. Neutron stars are so dense that a teaspoon of its material weight several billion tons.
    When many stars collapse to form neutron stars, like that figure skater pulling their arms in during a spin, the star spins faster and faster during its collapse. This may form a pulsar in which charged particles, accelerated to relativistic speeds, cause a kind of wind and a standing shock wave. The Crab Nebula contains such a pulsar as indicated in the above and below images. It was originally a normal star, over a million kilometers in diameter, however now, due to its supernova, it is only 28-30 kilometers in diameter, but spins at over 30 times each second. In the image below you can more clearly see this pulsar and some surrounding shock waves caused by the pulsar wind. This pulsar lights up the crab nebula with a ghostly bluish-white color. The red filaments are the remnants of the original star’s atmosphere and contain ionized helium and hydrogen along with some heavier elements.
    Since the Crab Nebula is so close the ecliptic (the plane in which the earth, moon, and all planets orbit), many solar system objects visually come close to the nebula during their orbits as seen from earth. In fact, Saturn passed in front of the Crab on January 4, 2003. In the image above, another solar system object is visible, and came very close to transiting M1, a couple days after this image. The object is identified as Asteroid 3409 Abramov. It is a stony Koronian asteroid about 11 kilometers in diameter, and orbits in the outer main asteroid belt between Mars and Jupiter, taking about 5 years to orbit the sun. Ironically it is not much smaller than the Crab Pulsar. However, at an average of 400 million kilometers away from us, 3409 Abramov is quite close compared the Crab which is 6500 light years away (150 million times further away that the asteroid). Click on the above image, zoom into the asteroid line caused by it moving during exposures and note the gap in the line. This was the 3-5 minutes it takes to flip the telescope mount when passing the meridian.
Optics: RC Optical System 20" F/8.2 (4165.6 mm Focal Length) Date: October 29-30, 2021
Camera: SBIG STXL-11000 with Adaptive Optics Location: Columbus, Texas
Exposure: LRGB = 320:90:80:110 minutes Imager: Kent E. Biggs