What is "guest star"

1914 in the entertainment sense; earlier the phrase was used literally, of novae. As a verb, by 1942.

n. 1 A guest on a TV programme who stars in one, or a few, episodes. 2 A guest on a recording

In Chinese astronomy, a guest star is a star which has suddenly appeared in a place where no star had previously been observed and becomes invisible again after some time. The term is a literal translation from ancient Chinese astronomical records.

Modern astronomy recognizes that guest stars are manifestations of cataclysmic variable stars: novae and supernovae. Still, the term "guest star" is used in the context of ancient records, since the exact classification of an astronomical event in question is based on interpretations of old records, rather than on direct observations.

In ancient Chinese astronomy, guest stars were one of the three types of "new stars", the other two (hui xing, “broom star”, a comet with a tail; xing bo, “fuzzy star”, a comet without a tail) being comets in modern understanding. The earliest Chinese record of guest stars is contained in Han Shu , the history of Han Dynasty (206 BCE – 220 CE), and all subsequent dynastic histories had such records. Of ancient European chronicles, the possible early indications at supernovae are vague. One likely reference of such an astronomical event could be the supernova of 185 CE recorded by Chinese. Some astronomers have questioned why the notable supernova of 1054 CE was missing from the European records.