China has a history of astronomy that’s over three and a half thousand years old, a stretch of time long enough to record many notable occurrences. They would name stars which suddenly appear in a place where no star had previously been observed and becomes invisible again after some time “Guest Stars”.

In 1054 one such guest star was first seen in the constellation of Taurus, one so bright that it was visible for a month during the daytime, and for two years in the night sky. This star was the explosion of a star which left behind the Crab Nebula, a six-light-year-wide field of glowing, supercharged gases.

X-ray Image: NASA/CXC/ASU/J. Hester et al.; Optical Image: NASA/HST/ASU/J. Hester et al.

At the heart of the Nebula is the city-sized Crab Pulsar, the rapidly spinning, ultra-dense core of the exploded star. The magnetized neutron star spins 30 times a second and ejects twin beams of radiation that make it appear to intensely pulse like a lighthouse. A “Crab” and “Milicrab” are sometimes used as standard astrophotometrical units for measurements. One Crab is defined as the intensity of the Crab Nebula at the corresponding X-ray photon energy.

Have a great day and take care of yourselves, everyone!