194 A CENTURY'S PROGRESS IN ASTRONOMY. 



slowly changing into that of a gaseous nebula. 

 In August and September 1901 the nebular 

 spectrum became more apparent. 



In August 1901 Wolf at Heidelberg discovered 

 a faint trace of nebula near the nova. On Sep- 

 tember 20 this nebula was photographed by 

 George Ritchey at the Yerkes Observatory, and 

 was seen to be of a spiral form. This was con- 

 firmed by Perrine, who also found, from plates 

 taken in November, that the nebula was moving 

 at the rate of eleven minutes of arc a year. 

 This extraordinary velocity was exceedingly 

 puzzling to astronomers, and at length Kapteyn 

 suggested that the nebula shone only by re- 

 flected light from the new star, and that the 

 apparent motion was an illusion caused by the 

 flare of the explosion travelling out from the 

 nova. 



On March 16, 1903, Herbert Hall Turner 

 (born 1861), Professor of Astronomy at Oxford, 

 discovered a new star of the seventh magnitude 

 in the constellation Gemini, from an examination 

 of photographic plates. Photographs taken at 

 Harvard showed that on March 1 it must have 

 been fainter than the twelfth magnitude, while 

 five days later it was of the fifth. In August 

 1903 Pickering found its spectrum nebular. In 

 August 1905 another small nova was found by 



