698 ' KANSAS CITY REVIEW OF SCIENCE. 



began to decrease in brightness — steadily growing dimmer for several months, 

 until about the middle of March, 1574, when it disappeared entirely; having thus 

 been visible, after a very sudden appearance, during a period of sixteen months. 

 This star was white when first observed ; it afterward changed to a red color, and 

 finally again to white. 



Old records indicate the observation of a similar star in nearly or quite the 

 same place in 1264, and 945. These dates indicate periods of 308 years and 319 

 years between the times of visibility of these grand stellar shows. Applying three 

 more such periods backward curiously enough brings us to about the time of the 

 birth of Christ ; when a bright star appeared as a guide to wise men in the East. 

 Now there are one or two other circumstances by which it might seem possible 

 to reconcile the "guiding star " with the one above described. The Nativity 

 was probably in the latter part of December, at which time Cassiopeia, and of 

 course any star in it, is on or near the meridian quite early in the evening; and 

 not very far from the zenith, though considerably north of it But as the night 

 goes on these stars appear to move westward on account of the earth's rotation ; 

 and further west also by reason of the earth's revolution around the Sun. The 

 place where the wise men lived and started from is perhaps 200 or 300 miles east- 

 erly from Bethlehem, and it would seem that their star " the guiding star" should 

 be westerly from them and move eastward, apparently, as they approached the 

 place where the young child was ; for when they arrived the star was over that 

 place. But may we not safely admit that the star which led the Magi to the in- 

 fant Jesus was a supernatural phenomenon in no way connected with the fixed 

 stars in the distant heavens ? Some persons have believed that the new stars of 

 1572, etc , were simply apparitions of the "Guiding Star" seen at Bethlehem, 

 so they, or it, has sometimes been called the "Star of Bethlehem," 



Other new or temporary stars have been seen at different times — notably in 

 1604, when a bright star blazed out rather suddenly in the constellation Ophiu- 

 chus; and one of less prominence was observed in Cygnus, May, 1866. 



Now, there are quite a number of stars which are always visible and yet are 

 known to change in brightness. They are called "variable stars." Prominent 

 among them is Algol, a star in Perseus, which commonly shines as one of the 

 second magnitude. But every three days (or rather two days and twenty hours), 

 the light of this star diminishes to that of the fourth magnitude, where it stays for 

 twenty minutes, and in three and one half hours resumes its wonted brightness. 

 A variable star in the Whale, called Mira, is invisible to the naked eye most of 

 the time. But about every eleven months it shines out with a brightness of 

 second or third magnitude; remaining so for about two weeks. It loses light 

 for three months and disappears to natural vision. In about five months after- 

 ward it becomes light enough to be just visible to the naked eye — a sixth magni- 

 tude star — a-nd reaches its maximum brightness in three months more. But the 

 changes of Mira are less regular than those of Algol. Its period is sometimes 

 longer, and other times shorter, than eleven months. Its greatest brightness is 

 sometimes that of second magnitude, and sometimes of only third magnitude. 



