STAR 



STAR 



E STORY OF THE STARS 



TAR, a heavenly body which appears 

 to us as a spot of twinkling light, quaintly de- 

 scribed by a child as "a hole in the sky." So 

 far as known, it is of the same composition as 

 the sun, which is itself a star. 



Stars are bodies which, like our sun, are in- 

 candescent, each shining with its own light. 

 The stars that can be seen with the naked eye 

 number between 6,000 and 7,000, but the num- 

 ber actually visible at one time is rarely more 

 than about 2,000. A powerful telescope soon 

 shows that those which can be seen with the 

 eye are only a small proportion of the number 

 really existing. A telescope like the great equa- 

 torial at Yerkes Observatory would show more 

 than 100,000,000, while even an opera glass of 

 average quality would make visible about 100,- 

 000. Photography has recently revealed many 

 millions of stars never before detected. From 

 the earth all stars look more or less alike to 

 the eye, varying principally in size and bright- 

 ness. Young, an American astronomer, says, 

 however, that stars differ among themselves in 

 size, color and brilliancy, "as much as flies 

 differ from elephants;" the Bible, too, uses as 

 a comparison, "as one star differeth from an- 

 other in glory." 



Grouping and Naming of Stars. Stars appear 

 to be naturally grouped in constellations, which 

 are given names mostly drawn from Greek 

 mythology. Sometimes the grouping of the 

 stars suggests the name given; at other times 

 the name does not appear appropriate or to 

 have been bestowed for any particular reason. 

 The stars themselves are being given special 

 names as rapidly as astronomers can catalog 

 them. Usually a star's name is that of the 

 constellation in which it appears plus a Greek 

 letter; thus Alpha Centauri is the first in Cen- 

 taurus. The subject of grouping and naming 

 is treated fully in the article ASTRONOMY, sub- 

 head The Stars and Their Names. 



Variable Stars. Stars which appear to change 

 their brightness, either slowly, regularly, or 

 continually, are called variable. They may 

 blaze out suddenly and disappear, grow bright 



and dull alternately, or slowly fade. Many 

 explanations have been suggested concerning 

 the causes of these changes. "When the stars 

 grow old," is not as fanciful an expression as it 

 might seem; the changes, when merely pro- 

 gressive, are due to age, while the periodical 

 darkening of stars is attributed to an eclipse 

 by some intervening opaque body. 



Size of Stars. The measurement of stars is 

 in many cases almost impossible. The appar- 

 ently tiny spots yield practically no basis for 

 calculation. It has been carefully estimated, 

 however, by use of the spectroscope, that Algol, 

 a bright star in the constellation of Perseus, 

 has a diameter of 1,160,000 miles, or about 140 

 times the diameter of the earth. Algol has a 

 companion star, invisible to all but the most 

 powerful instrument, with a diameter of nearly 

 1,000,000 miles. The diameter of the sun is 

 108 times that of the earth, yet Arcturus has a 

 diameter 100 times greater than that of the 

 sun. 



Magnitude. In respect to the degrees of 

 brightness with which they shine, stars are di- 

 vided into magnitudes. The human eye can- 

 not discern stars beyond the sixth magnitude, 

 and the largest telescopes do not reveal any 

 lower than the fifteenth. Stars of the first 

 magnitude shine about one hundred times as 

 brightly as those of the sixth, and their light 

 is perhaps a million times as intense as those 

 of the fifteenth. From the days of the Greek 

 astronomer Hipparchus, in the second century 

 B. c., catalogs of stars have been compiled from 

 time to time. The following table is a recent 

 one, but, as estimates are being constantly re- 

 vised, it must be considered subject to change: 



20 



Stars of first magnitude 

 " second 

 " third 

 ' " fourth 

 " fifth 

 " sixth 

 " seventh 

 " eighth 

 " ninth 

 " tenth 

 " eleventh 



65 



190 



425 



1,100 



3,200 



13,000 



40,000 



120,000 



380,000 



1,000,000 



