APOD: 2022 August 21 - The Spinning Pulsar of the Crab Nebula

Good afternoon, Rallypoint, and welcome to a backlog edition (August 15-21) of Astronomy Picture of the Day (APOD). We'll begin with today's image: "The Spinning Pulsar of the Crab Nebula." A pulsar can be thought of as an astronomical lighthouse. First, it is a collapsed core of a large star that exploded. Gravity contracts the surviving matter into a ball 36-40 miles in diameter that becomes as dense as atomic nuclei with an overall mass slightly greater than our Sun. Second, the pulsar spins. How to we know this? We detect electromagnetic radiation "pulses" when the magnetic poles of the pulsar are oriented towards Earth. In the case of the Crab Nebula Pulsar, we know it is spinning 30 times per second.

In July 1054. Chinese astronomers noted a "guest star" in the constellation Taurus. For almost a month, this star was even visible during daylight hours. We now recognize this "guest star" as the Crab Nebula (M1), located some 6,500 years from Earth. It was first discovered in 1731 by English doctor and astronomer John Bevis. Charles Messier independently rediscovered it in 1758 while searching for the predicted reappearance of Halley's Comet. Today's APOD is a composite image based on visible light from the Hubble Space Telescope (HST), x-ray data from the Chandra X-Ray Observatory (CXO), and infrared data from the Spitzer Space Telescope (SST).