MIRACLES OF SCIENCE 



tauri, as we have seen, is a very neighborly star, the 

 second nearest star being more than twice as dis- 

 tant. So it is quite beyond the range of present 

 comprehension that any means should ever be de- 

 veloped through which astronomers here on the earth 

 could demonstrate the presence of bodies compar- 

 able in size to the earth and its sister planets in con- 

 nection with the stellar systems. 



But while it thus remains an open question as to 

 whether there are small planets revolving about any 

 star other than our sun, it is not at all in doubt that 

 there are vast numbers of stars that are grouped 

 into systems of a different order, comprising two or 

 more stellar bodies of somewhat similar size and 

 therefore making up systems which are to be likened 

 to the relations of the earth and the moon rather 

 than of the sun and planets. These systems have 

 already been referred to as double stars. 



The discovery that such double stars exist was 

 made by Sir William Hershel more than a century 

 ago. From that day to this the discovery of double 

 stars has gone on, and, as we have seen, it is now 

 known that this condition appears to be the rule 

 rather than the exception in the sidereal universe. 

 In some cases two stars more or less equal in 

 brilliancy are observed to be revolving in a mutual 

 orbit in such manner as to leave it scarcely open to 

 doubt that the laws of inertia and of gravitation de- 

 termine their orbits precisely as the same laws 

 determine the orbits of planets about the sun and 

 of satellites about the planets in our solar system. 

 ar other cases in which the backward and 

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