Identification of the pulsar PSR1509–58 with the 'guest star' of AD 185

Abstract

ON 7 December 185, astronomers at the imperial observatory of Lo-Yang, in central China, reported a 'guest star' in the southern sky. Their records of its appearance, gradual fading and disappearance constitute the oldest compelling historical account of a supernova. It is widely believed that the remnant of this explosion is MSH14–63, but the identification is problematic, in particular because the position of MSH14–63 with respect to the Sun and the horizon would have made it invisible for some of the time when the guest star was said to be visible. I argue here that the Chinese astronomers actually witnessed the birth of the pulsar PSR1509–58 in the supernova remnant MSH15–52. This is then only the second pulsar, after that in the Crab nebula (PSR0531 + 21), to have a known age. Timing measurements of the age of PSR1509–58 are consistent with its birth ∼1,800 years ago, and future measurements of the distance to MSH15–52 and its rate of expansion should conclusively establish or disprove this identification.