POPULAR SCIENCE 



NEW STARS 



By the Rev. A. L. CORTIE, S.J., F.R.A.S., F.Inst.P. 



One of the most wonderful of the phenomena which can be 

 observed in the starry firmament is the sudden blaze into 

 luminosity of a new or temporary member of the starry hosts, 

 which have, so far as visual observations are concerned, shed 

 their light upon mankind, unaltered in relative position or in 

 number, for untold centuries. It may happen that the new 

 star suddenly appears in a position in the sky which was un- 

 occupied by any star before. Or if a star existed, it had not 

 been previously detected, owing to its excessive faintness, by 

 any observation, visual or photographic, anterior to its sudden 

 increase of lustre. Nova Aurigae, for instance, discovered by 

 the Rev. Dr. Thomas W. Anderson, of Edinburgh, in the last 

 days of January 1892, was absent from a plate of the region 

 of the sky in which it shone forth, taken by Dr. Max Wolf, of 

 Heidelberg, on December 8 of the preceding year, on which 

 stars were photographed as faint as the eleventh magnitude.^ 

 Two days later it was of magnitude 5 on plates taken at 

 Harvard College Observatory by Prof. E. C. Pickering. This 

 means that the star had increased its luminosity two hundred 

 and fifty fold in two, days. In the case of Nova Persei, also 

 discovered by Dr. Anderson, a plate of the region of the sky 

 in which it shone, taken by Mr. Stanley Williams on February 

 20, 1 90 1, failed to record the new star, though stars as faint 

 as the twelfth magnitude were shown. Two da3^s later it was 

 a magnitude brighter than a first magnitude star, which indi- 

 cates an enormous increase in light, fully sixty thousand fold. 

 Nova Cygni (1920) ^ also was presumably, if it existed at all 

 as a luminous body, below the sixteenth magnitude prior to 



^ The lowest star magnitude visible to the naked eye is the sixth. The 

 re latio n of brightness between one magnitude and the next in order is 

 !^ioo, nearly 2-5. 



2 A plate of the field taken at Heidelberg, June 3, 1905, which shows 

 stars of magnitude 16, has no trace of the nova. The Observatory, No. 557, 

 p. 367. October 1920, 



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