The Great Comet of 1556 is a famous comet that first appeared in February 1556.
The Great Comet of 1556, known as C/1556 D1 in modern nomenclature, appears to have been seen in some places before the end of February; but it was not generally observed until the middle of the first week in March. Its apparent diameter was equal to half that of the Moon, and the tail resembled " the flame of a torch agitated by the wind,"—an expression doubtless referring to the coruscations which are sometimes visible in the tails of comets. Cornelius Gemma (the son of Gemma Frisius) says, the head of the comet, when it first appeared, was fully as large as Jupiter; its color resembled that of Mars.
The course of the comet of 1556 was observed by Paul Fabricius, a mathematician and physician at the court of Charles V, Holy Roman Emperor.
Great Comet of 1556 Wikipedia
The Great Comet of 1556 is called the comet of Charles V. When the Emperor first caught sight of it he stood aghast, and exclaimed: "By this dread sign my fates do summon me". Charles had long meditated about retiring from the world he had conquered and crushed. Regarding the comet as a sign of Heaven's command to do so, he hastened towards the peaceful monastery of St. Juste, Placentia.
An English treatise (anonymous) on "Blazing Stares" (1618) speaks of the comet as follows :
The Portuguese Dominican friar Gaspar da Cruz, who visited Guangzhou in 1556, associated the comet with the devastating 1556 Shaanxi earthquake. In his 1569 book he wondered if the comet was a sign of calamities not just for China, but for the entire world - and could be even the sign of the birth of Antichrist.
Grounding his calculations upon elements deduced from Conrad Wolfhardt's chart along with some other crude data gathered from old records, and comparing the result he obtained with the account given by Friar Giles of Cambridge of a grand comet which appeared in 1264, John Russell Hind was led to conclude, as Richard Dunthorne had been in the previous century, that the comet of Charles V. was that of 1264 returned. At any rate, he found a high degree of probability in favor of the conclusion at which he had arrived, and warmly gave support to the view that the bodies of these years were identical. Hence he concluded that a return to perihelion might be looked for about the middle of this century, 1848 to 1850. So far no observed comet has matched the orbital elements of either comet and David A. Sargent writes that available evidence points to there being no connection between the two.