ASTRONOMY WITH AN OPERA-GLASS. 



527 



Between the stars Delta (8) and o' and o" there is a remarkable array 

 of minute stars, as shown in the accompanying cut. One never sees 

 stars arranged in streams or rows, like these, without an irresistible 

 impression that the arrangement can not be accidental ; that some 

 law must have been in operation which associated them together in 

 the forms which we see. 'Yet, when we reflect that these are all suns, 

 how far do we seem to be from understanding the meaning of the uni- 

 verse. 



The extraordinary size and brilliancy of Sirius might naturally 

 enough lead one to suppose that it is the nearest of the stars, and 

 such it was once believed to be. Observations of stellar parallax, 

 however, show that this was a mistake. The distance of Sirius is so 

 great that no satisfactory determination of it has yet been made. We 

 may safely say, though, that that distance is, at the least calculation, 

 50,000,000,000,000 miles. In other words, Sirius is about 537,000 times 

 as far from the earth as the sun is. Then since light diminishes as the 

 square of the distance increases, the sun, if placed as far from us as 

 Sirius is, would send us, in round numbers, 288,000,000,000 times less 

 light than we now receive from it. But Sirius actually sends us only 

 about 4,000,000,000 times less light than the sun does ; consequently 



, . 288,000,000,000 

 Sinus must shme — 4 qqo qqq oqq ~'<^^ times as brilliantly as the sun. 



If we adopt Wollaston's estimate of the light of Sirius, as compared 

 with that of the sun's, viz., ao.ouorofo.ooo; ^^ shall still find that the 

 actual brilliancy of that grand star is more than fourteen times as 

 great as that of our sun. But as observations on the companion of 

 Sirius show that Sirius's mass is fully twenty times the sun's, and since 

 the character of Sirius's spectrum indicates that its intrinsic brightness, 

 surface for surface, is much superior to the sun's, it is probable that 

 our estimate of the star's actual brilliancy, as compared with what the 

 sun would possess at the same distance, viz., seventy-two times, is much 

 nearer the truth. It is evident that life would be insupportable upon 

 the earth if it were placed as near to Sirius as it is to the sun. If the 

 earth were a planet belonging to the system of Sirius, in order to enjoy 

 the same amount of heat and light it now receives, it would have to be 

 removed to a distance of nearly 800,000,000 miles, or about 8^ times 

 its distance from the sun. Its time of revolution around Sirius Avould 

 then be nearly 5^ years, or, in other words, the year would be length- 

 ened 5^ times. 



But, as I have said, the estimate of Sirius's distance used in these 

 calculations is the smallest that can be accepted. Good authorities re- 

 gard the distance as being not less than 100,000,000,000,000 miles ; in 

 which case the star's brilliancy must be as much as 228 times greater 

 than that of the sun ! And yet even Sirius is probably not the great- 

 est sun belonging to the visible universe. There can be little doubt 

 that Canopus, in the southern hemisphere, is a grander sun than Sirius. 



