POPULAR ASTRONOMY 



327 



But even at this enormous distance, 

 the sun would be only about one-sixth 

 as far away as Sirius exactly lies. In 

 other words, Sirius shines with a lus- 

 tre fully thirty times that of our sun. 

 And Sirius is not a solitary example. 

 The sun looks big and bright only be- 

 cause it is so close, but if it could be 

 put off from us to the average distance 

 of the fixed stars, it would shine with 

 a luminosity just visible to the naked 

 eye, it would be a star of about the 

 sixth magnitude. There are vast num- 

 bers of other suns more brilliant and 

 more massive than our own sun. 

 NEW STARS. 



Another new star has been found at 

 the Harvard College Observatory, the 

 third of these bodies in a period of 

 six weeks. When a star suddenly 

 blazes out and increases its brightness 

 in a remarkable manner in a short 

 period of time, it is called a "new" star 

 or "Nova." The brightness usually 

 lasts but a short time, and the star 

 again sinks to its former state of com- 

 parative obscurity. During the past 

 twenty-five years only seventeen new 

 stars have been found altogether, of 

 which number no less than fourteen 

 have been found at Harvard. The last 

 addition was found by Miss A. J. Can- 

 non, but the interesting part of its life 

 history — the period of maximum 

 brightness — was seen many years ago. 

 The discovery was made in November. 

 1910, from a study of photographs 

 made on August 10, 1899. The star 

 appeared in the constellation Sagit- 

 tarius from that date until October, 

 1901. The star cannot be found in the 

 constellation now. It is very curious 

 that three such unusual discoveries 

 should be crowded into six weeks. 



A comet has been discovered with 

 the great 36-inch telescope of the Lick 

 Observatory. This is a return of 

 Brook's Periodic Comet, 1889 V, 

 which re-visits the earth every seven 

 years. The comet was found within 

 thirty seconds of arc of its predicted 



place (one-sixtieth part of the diame- 

 ter of the moon), but it is unfavorably 

 situated and cannot be seen in small 

 telescopes. 



Some years ago Professor Charles 

 Lane Poor of Columbia University 

 showed that this comet in March, 1883, 

 came very close to the great planet 

 Jupiter. Before this date the comet 

 had a period about the sun of more 

 than a hundred years, but the attrac- 

 tion exerted by Jupiter was so strong 

 that the comet was pulled out of its 

 former orbit, was "captured" and made 

 a permanent member of "Jupiter's 

 family." The comet was observed in 

 1889, 1896, 1903, and now in. 1910. This 

 comet has afforded a splendid example 

 of the manner in which comets are 

 brought into the solar system, and the 

 interest attaching to it is great on that 

 account. 



THE PLANETS. 



Mercury may be seen in the south- 

 west about Christmas day setting an 

 hour after sunset. Venus is still too 

 near the sun to be visible. 



Mars is a moving star rising an hour 

 and a half before the sun, but it is faint 

 and uninteresting. 



Jupiter rises two or three hours be- 

 fore sunrise and during the winter will 

 become more and more prominent. 



Saturn is still a magnificent object 

 for a small telescope. It rises about 

 sunset and can be readily found by any 

 one, the brightest body last of the mer- 

 idian. The possessors of telescopes will 

 have continued pleasure in examining 

 it closely. Additional interest is at- 

 tached to it, now due to the presence 

 of a polar cap discovered at the Lick 

 Observatory. 



The sun is at the winter solstice on 

 December 22 at 10.12 a. m. This is the 

 "shortest day in the year," the day of 

 least sunlight. By consulting any ordi- 

 nary almanac it will be seen that the 

 sun does not rise the latest nor set the 

 earliest for the year on this date. What 

 is the reason? 





