ARE THERE PLANETS AMONG THE STARS? 



73 



Dr. See are; but, at any rate, we can safely assume that they are 

 at the distance of the nearest stars, say somewhere about three hun- 

 dred thousand times the earth's distance from the sun. The sun 

 itself removed to that distance would appear to our eyes only as a 

 star of the first magnitude. But Zollner has shown that the sun 

 exceeds Jupiter in brilliancy 5,472,000,000 times. Seen from equal 

 distances, however, the ratio would be about 218,000,000 to 1. This 

 would be the ratio of their light if both sun and Jupiter could be 

 removed to about the distance of the nearest stars. Since the sun 

 would then be only as bright as one of the stars of the first magni- 

 tude, and since Jupiter would be 218,000,000 times less brilliant, 

 it is evident that the latter would not be visible at all. The faintest 

 stars that the most powerful telescopes are able to show probably do 

 not fall below the sixteenth or, at the most, the seventeenth magni- 

 tude. But a seventeenth-magnitude star is only between two and 

 three million times fainter than the sun would appear at the distance 

 above supposed, while, as we have seen, Jupiter would be more than 

 two hundred million times fainter than the sun. 



To put it in another way: Jupiter, at the distance of the nearest 

 stars, would be not far from one hundred times less bright than the 

 faintest star which the largest telescope is just able, under the most 

 exquisite conditions, to glimpse. To see a star so faint as that would 

 require an object-glass of a diameter half as great as the length of 

 the tube of the Lick telescope, or say thirty feet ! 



Of course, Jupiter might be more brilliantly illuminated by a 

 brighter star than the sun; but, granting that, it still would not be 

 visible at such a distance, even if we neglect the well-known conceal- 

 ing or blinding effect of the rays of a bright star when the observer 

 is trying to view a faint one close to it. Clearly, then, the obscure 

 objects seen by Dr. See near some of the stars, if they really are 

 bodies visible only by light reflected from their surfaces, must be 

 enormously larger than the planet Jupiter, and can not, accordingly, 

 be admitted into the category of planets proper, whatever else they 

 may be. 



Perhaps they are extreme cases of what we see in the system of 

 Sirius i. e., a brilliant star with a companion which has ceased to 

 shine as a star while retaining its bulk. Such bodies may be called 

 planets in that they only shine by reflected light, and that they are 

 attached to a brilliant sun; but the part that they play in their sys- 

 tems is not strictly planetary. Owing to their great mass they bear 

 such sway over their shining companions as none of our planets, 

 nor all of them combined, can exercise; and for the same reason 

 they can not, except in a dream, be imagined to possess that which, 

 in our eyes, must always be the capital feature of a planet, rendering 



