ARE THERE PLANETS AMONG THE STARS? 171 

 AKE THERE PLANETS AMONG THE STARS? 



By GAEEETT P. SEEVISS. 



THIS always interesting question has lately been revived in a 

 startling manner by discoveries that have seemed to reach 

 almost deep enough to touch its solution. The following sen- 

 tences, fresh from the pen of Dr. T. J. J. See, of the Lowell 

 Observatory, are very significant from the point of view of our 

 inquiry : 



" Our observations during 1896-'97 have certainly disclosed stars 

 more difficult than any which astronomers had seen before. Among 

 these obscure objects about half a dozen are truly wonderful, in that 

 they seem to be dark, almost black in color, and apparently are shin- 

 ing by a dull reflected light. It is unlikely that they will prove to 

 be self-luminous. If they should turn out dark bodies in fact, shin- 

 ing only by the reflected light of the stars around which they revolve, 

 we should have the first case of planets dark bodies noticed among 

 the fixed stars." 



Of course, Dr. See has no reference in this statement to the 

 immense dark bodies which, in recent years, have been discovered 

 by spectroscopic methods revolving around some of the visible stars, 

 although invisible themselves. The obscure objects that he describes 

 belong to a different class, and might be likened, except perhaps in 

 magnitude, to the companion of Sirius, which, though a light-giving 

 body, exhibits nevertheless a singular defect of luminosity in rela- 

 tion to its mass. Sirius has only twice the mass, but ten thousand 

 times the luminosity, of its strange companion! Yet the latter is 

 evidently rather a faint, or partially extinguished, sun than an 

 opaque body shining only with light borrowed from its dazzling 

 neighbor. The objects seen by Dr. See, on the contrary, are " ap- 

 parently shining by a dull reflected light." 



If, however (as he evidently thinks is probable), these objects 

 should prove to be really non-luminous, it would not follow that 

 they are to be regarded as more like the planets of the solar system 

 than like the dark companions of certain other stars. A planet, in 

 the sense which we attach to the word, can not be comparable in mass 

 and size with the sun around which it revolves. The sun is a 

 thousand times larger than the greatest of its attendant planets, 

 Jupiter, and more than a million times larger than the earth. It 

 is extremely doubtful whether the relation of sun and planet could 

 exist between two bodies of anything like equal size, or even if one 

 exceeded the other many times in magnitude. It is only when the 

 difference is so great that the smaller of the two bodies is practically 



