186 ANNUAL REPORT SMITHSONIAN INSTITUTION, 192 8 



Ther'e are a thousand or more variables of this type whose activi- 

 ties take place in periods of about a year. They are exceedingly 

 interesting as being at the earliest stage of stellar existence ; they are 

 the youth of the skies, just stepping upon the threshold of celestial 

 splendors. From the darkness of space they have suddenly emerged 

 to take up their light-giving activities for billions of years. 



In the 200 years following the discovery of Mira a few new varia- 

 bles, mostly of the same class, were discovered. It remained for two 

 keen-eyed 3'Oung men, friends and neighbors, John Goodricke and 

 Edward Pigott, of York, England, to open the field of short-period 

 variation of stars. Such variables, with periods from a few hours 

 to 50 days, have been responsible for much of the knowledge which 

 we now have concerning the properties and ages of the stars, their 

 interiors, tlieir distances, and the extent of the universe. Stars that 

 are in action, such as variables, give opportunity to apply physical 

 laws and deduce results as to the conditions prevailing there. They 

 are the Avorking laboratories of the sky where the astronomer may 

 actually observe changing conditions. In our terrestrial laboratories 

 we can vary conditions of pressure, density, and temperature for 

 various sources at will to suit the investigation, but in the stellar 

 laboratories we must depend upon the variable stars to make the 

 manipulations for us. 



Edward Pigott was the son of a surveyor who had some small 

 astronomical instriunents and had used them to observe the stars 

 and planets. The son seems to have inherited his interest in astron- 

 omy from his fatlier and was accustomed to make observations at 

 his own liome. His knowledge of the heavens attracted to him Jolin 

 Goodricke, the son of a neighboring lord, who is one of the most 

 extraordinary characters in the history of science. Born a deaf- 

 mute, he received, nevertheless, a good education and became espe- 

 cially proficient in mathematics. In 1782, when he was but 18 years 

 of age, he took up the observation of Algol at the home of his friend, 

 Edward Pigott. In a short time he had found its period of varia- 

 tion by comparing its brightness with that of near-by stars. Its 

 variation was small, only 1.2 magnitudes, which makes the difficulty 

 of observation very much greater than that of tlie variables of the 

 type of Mira, where the variation is 5 or 6 magnitudes. He found 

 the i^eriod to be 2 days 20 hours 49 minutes, which was so much 

 shorter than that of any variable known before that the observation 

 was doubtless looked upon with reserve by the scientists of the Royal 

 Society to whom he communicated his results. In that early day, 

 when physical double stars were scarcely known, he boldly concluded 

 that the light changes were the result of an eclipse of the star by a 

 darker companion which was describing an orbit about it in such an 

 unexpectedly sliort time. It was 100 years before this remarkable 



