Star of Bethlehem
2 of the 7 encyclopedias on this shelf carry an entry for Star of Bethlehem. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
the star seen in Bethlehem by the wise men of the east when Christ was born. St. Matthew tells of how, when they had seen it, they told Herod who inquired of them at what time the star appeared. "And he sent them to Bethlehem, and said, Go and search diligently for the young child and when ye have found him bring me word again that I may come and worship him also. When they heard the king they departed, and, lo, the star, which they saw in the east, went before them till it came and stood over where the young child was. When they saw the star they rejoiced with exceeding great joy." Many theories are advanced to account for this phenomenon other than by attributing to it a supernatural or miraculous origin. Some have suggested that it might have been a comet; others that it belongs to the class of novae or temporary stars which have for many years been observed to blaze out suddenly and then gradually disappear. Indeed the Star of Bethlehem has been thought, on quite insufficient grounds, however, to be identical with the nova discovered in 1572 by Tycho Brahe in the constellation Cassiopeia and known as "Tycho's Star." For some days this wonderful temporary star was as bright as Venus. There was among the superstitious a notion not only that this was the Star of Bethlehem, but that it would reappear to herald the second advent of the Lord. The Star of Bethlehem is also supposed to have been one of the larger planets. None of these explanations, however, is considered adequate.
Collier's New Encyclopedia (1921)
the celestial phenomenon described in the New Testament as accompanying the birth of Christ. Some astronomers have attempted to account for this on the hypothesis of the conjunction of two or more bright planets in about the same part of the sky at that time, but with little success. At various times since the appearance of Tycho Brahe's star in the constellation Cassiopeia in 1572, the celebrated Nova of that year, it has been suggested that this might be a variable star of long period, though there is nothing now in the vicinity of the place of this star brighter than the 12th or 13th magnitude. Astronomers, since the invention of the telescope, have kept a pretty close watch of the few faint stars in the immediate vicinity of the place indicated by Tycho Brahe's measures to see if any of them changed in brightness, but without any evidence of such change. There is no good reason for supposing any such periodicity in the star, or any other star now known.