MASSKS OF XISLAI, l;l^^\R^- STARS. 4^ 



/ 



as it is could not have evolved from a solar type star bv a process 

 of cooling. 



The spectral class K2 shows a general faintness towards the violet 

 end ; bands K and H are very strong. 



Antares. — Magnititd'e 1.22. Spcctnnit. Ma, peculiar. 



This bright star has a 7.0 magnitude companion of a bltiish 

 tint at 3". I distance. Neither angle nor distance are changing, 

 or if the angle is changing, the change is under o''.o5 a year. It 

 is remarkable that when the colours of a double star are con- 

 trasted there is seldom atiy motion, and no orbit has yet been 

 found for stich a pair. (Jn the contrary, in the cases of well- 

 known binary pairs, the htie or colours of the stars is almost 

 identical. In a Centaurus botli stars are yellow, btit the fainter 

 star is decidedly yellower, the respective spectra being Go and 

 K5. or in contiguous classes, and even this slight difference is 

 unustial, the fainter comj^onent of a double star being usu- 

 ally bluer than the brighter. Antares and its companion have a 

 small common proper motion which is more than large enotigh to 

 make it certain that they form a system, but the bond of union 

 is not that of gravitation. The spectrum is peculiar in showing- 

 indications of an A type spectrum, in addition to an ordinary Ma 

 spectrum, btit this is probably due to the companion, which is 

 perhaps not so faint as 7.0 magnitude. It is probable that the 

 strongly absorbing atmosphere of Antares, as indicated by its 

 spectrum, reduces its magnitude by three steps at least, so that, 

 were it not for its absorbing atmosphere, it would shine as a star 

 of the -T.8 magnittide. A solar-type star of that magnitude 

 would cause a com]:)anion at 3" to move over from 30 to 9c 

 degrees a year. There is no such motion ; the inference cannot 

 be avoided, namely, that Antares and its companion have exceed- 

 ingly small gravitative ])ower, of if they have it, that it is in 

 some way neutralised by some other force. 



Dr. Coblenz, of Washington, lias recently put a new instru- 

 ment at the disposal of astronomers which measures the total 

 intensity of radiation. With this instrument it is fottnd that if 

 otir eyes had the same sensitivity curve as the radiometer, An- 

 tares and Betelgeux would be the two brightest stars in the sky. 

 Hence we must conclude that stellar radiant energy is not related 

 in any simple way to gravitative power. For a description of the 

 new " stellar radiometry '' reference may be made to Dr. Kevin 

 Burns's ]Daper in the June number of the Publications of the 

 Asfroiioiiiical Society of fJie Pacific. 



The si)eclruni Afa is handed: the two hands faintly seen in K5 are 

 now well marked. 



a Hercules. — Magnitude 3.31 { conihoneufs 3.46 and 5.54). 



Spectrum Mb and {A). ' 



The principle star is variable (3.1 to 3.9), and the com- 

 panion is 4". 6 distant. They form a system because they have 

 common proper luotion. The position is slowly changing, btit. 



