560 THE VISIBLE STARS. 



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Professor Bessel found that the angle contained by those two lines, drawn ' 

 from the star in question to the opposite sides of the orbit, contained an angle , 

 amounting to two thirds of a second, and, consequently, that the angle included ' 

 by the lines between the sun and the earth would form one third of a second. ! 

 From this it would follow, that the distance from the star, being the radius of a 

 circle, of which the distance between the earth and sun is an arc of one third 

 of a second, will be 618,795 times the length of the earth's distance from the sun. 

 Taking round numbers, then, it will follow from this observation that the dis- 

 tance of this star is 600,000 times greater than the distance of the earth from 

 the sun. But the distance of the earth from the sun being 100 millions of miles, 

 it will follow that the distance of the star must be sixty millions of millions of 

 miles. 



Such is the nearest approximation that observation has supplied for the space 

 that separates the solar system from other bodies of the universe. 



Minds unaccustomed to the contemplation of great numbers and magnitudes 

 are overwhelmed in their efforts to conceive such distances ; and even astron- 

 omers have been compelled to resort to extraordinary expedients to express and 

 conceive clearly such spaces. 



On another occasion we have shown that light moves through space at 

 the rate of 200,000 miles per second. This motion of light has accordingly 

 been adopted as the most convenient modulus for expressing the distances of 

 the stars ; and we are accustomed to express them by saying how long light 

 would take to move over them. If, then, sixty millions of millions of 

 miles be divided by 200,000 we shall obtain the number of seconds which 

 light would take to come from the nearest star to the solar system ; and if this 

 number of seconds be, in the usual manner, reduced to years, it will be found 

 that light would take about ten years to travel from the nearest star to the 

 earth. Such is, then, the space that divides us from them. 



To conceive this prodigious distance more clearly still, it has been calcula- 

 ted that a cannon-ball, which moves with a velocity of 500 miles an hour, 

 would take to travel from the nearest star to the earth, an interval of 14,255,418 

 years. Again : it has been computed that a steam-carriage starting from the 

 earth, and moving toward the star at the rate of 20 miles an hour, would take 

 to reach the star, 356,385,466 years; a period of time 61,000 times greater 

 than the whole interval since the creation of the world, according to Mosaic 

 chronology. 



But this is only the interval that separates our system from the nearest stars. 

 Analogy and all the grounds of probability lead to the conclusion that corre- 

 sponding intervals separate the stars from each other. We shall hereafter see 

 that the stars are, in fact, suns like our own, or, what is the same, that our sun 

 is a star ; and it is consistent and natural to suppose our sun is no farther re- 

 moved from the stars than the stars are from each other. 



Among the multitude of stars which we behold in the firmament we find 

 a great variety of splendor. Those which are the brightest and largest, and 

 which are said to be of the first magnitude, are few ; the next in order of 

 brightness, which are called of the second magnitude, are more numerous ; and 

 as they decrease in brightness their number rapidly increases. 



The number of stars of the first magnitude does not exceed twenty ; those of 

 the second, fifty ; those of the third, two hundred ; and so on, the number of 

 the smallest being incapable of estimation. 



The stars which are capable of being seen by the naked eye are usually re- 

 solved into seven orders of magnitudes the first being the brightest and largest, 

 while those of the seventh magnitude are the smallest that the eye can dis- 

 tinctly see. 



