468 



SCIENCE 



[Vol. LV, No. 1427 



with anticipation. (The writer of this article 

 looks back with anything bnt the keenest of 

 joy to working for thirteen hours at night at 

 the Yerkes Observatory with the thermometer 

 at twenty-six degrees Fahrenheit below zero). 

 Very frequently the keenness of the astro- 

 nomical thrills becomes gradually dulled, the 

 small telescope has not sufficient power to show 

 the more remarkable objects in the sky, clouds 

 and cold weather interfere with observing — 

 and soon the telescope is brought out but sel- 

 dom, and finally is offered for sale. 



Many of these amateur star-gazers might 

 have bad their interest continued if only their 

 work at night could have had some object other 

 than personal pleasvire. The American Asso- 

 ciation of Variable Star Observers has been of 

 very great value to astronomy by organizing 

 the owners of two-, three-, four- or five-inch 

 telescopes and showing them how they can co- 

 operate with the professional astronomer using 

 larger telescopes to observe the class of objects 

 in the sky known as variable stars. As their 

 name signifies, these stars vary in bright- 

 ness, sometimes being bright, sometimes much 

 fainter. There are more than three thousand 

 of such stars known in the the sky. The varia- 

 tions of some stars like Betelgeuse, /? Lyrje or 

 8 Cephei can be followed by the naked eye, 

 some of the stars at minimum brightness can 

 be seen with a five-inch telescope, while others 

 become so faint at minimum that they are 

 almost or quite invisible in the largest telescope 

 in existence. Some of these variables have a 

 period from maximum to minimum which is 

 quite short, measured by an interval of a iew 

 hours or a few days in length, some of the 

 periods are measured in hundreds of days. 

 Some of the periods are quite regular, some 

 are very irregular. The well-known Algol 

 changes in brightness by one component eclips- 

 ing 'the other. There are other stars like 

 SS Cygni, V. Geminorum, and SS Aurigse that 

 are normally faint, and suddenly and for some 

 reason for which as yet we have no adequate 

 explanation greatly augment their brilliancy, 

 the last of the three stars named above 

 may increase its brightness one hundredfold in 

 twenty-four hours. There are thus many varie- 

 ties of variable stars most of which need careful 



and systematic observation, and consequently 

 an observing program can be chosen which 

 can be adapted to the aperture of the telescope 

 used. 



Largely through the enthusiastic efforts of 

 Wm. Tyler Oleott of Norwich, Conn., the 

 American Association of Variable Star Ob- 

 servers (or the A. A. V. S. 0.) was organized 

 in 1911 with seven observers. In ten years the 

 membership has grown to three hundred, and 

 the total observations made has the amazing 

 number of 120,000. The present plan of the 

 A. A. V. S. 0. is that its members are observing 

 systematically the changes in brightness of 

 more than three hundred stars of long period. 

 The stars under observation can be followed 

 until with diminishing brightness they become 

 invisible with the small apertures employed. 

 These stars, however, can still be seen with 

 telescopes of larger size in the hands of the 

 professional astronomer. By a plan of coop- 

 eration, therefoi'e, the members of the 

 A. A. V. S. 0. can observe the variables when 

 bright while Harvard with its twelve or fifteen- 

 inch telescope and the McCormick Observatory 

 with its still larger aperture of twenty-six 

 inches can observe when faint, and thus the 

 stars can be kept under almost continual ob- 

 servation, except when the stars are too near 

 the sun. Each month each observer sends his 

 observations to Harvard College Observatory 

 where the observations are collected together 

 and are then published in Popular Astronomy. 

 This immediate publication is of great value in 

 keeping alive the interest of the amateur for 

 each observer can see that his observations are 

 of value in fixing the brightness of the stars 

 and even the beginner can experience the thrill 

 of finding that his observations jjerhaps fit in 

 beautifully with the magnitudes determined by- 

 observers of greater skill. 



Professor Edward C. Pickering, the late 

 director of Harvard College Observatory, was 

 keenly enthusiastic about the work of the 

 A. A. V. S. 0. for he recognized the very great 

 value of this organization. And now to per- 

 petuate its work and to increase its value to 

 astronomy the Association of Variable Star 

 Observers is asking for an endowment to bear 

 the name, the Edward C. Pickering Memorial. 



