Apeil 17, 1903. J 



SCIENCE. 



611 



measurement, carrying over four thou- 

 sand images of the asteroid. The measure- 

 ment and reduction of these plates will be 

 an enormous task. Fortunately, Professor 

 Rees, director of Columbia College Ob- 

 servatory, has agreed to undertake that 

 work. His eiBcient bureau of measure- 

 ment and reduction, in immediate charge 

 of Professor Jacoby, has already measured 

 and reduced a number of the plates. 



Perhaps the most interesting astronom- 

 ical events of recent years relate to the new 

 star in Perseus, discovered in Edinburgh 

 on February 22, 1901. The Lick Observa- 

 tory, in common with all similar institu- 

 tions, made immediate plans to bring every 

 available resource to bear upon the study 

 of this star. Its position was measured 

 by Mr. Tucker with the meridian circle, 

 and by Mr. Aitken with the thirty-six-inch 

 equatorial on 'several occasions in the 

 spring and summer of 1901. It is clear 

 from their observations, amply confirmed 

 by those made elsewhere, that the new star 

 is at least as far away as the faint stars 

 surrounding, it, and that its motion with 

 reference to the surrounding stars is so 

 slight as to elude detection for the present. 

 The spectroscopic observations by Messrs. 

 Campbell, Wright, Reese and Stebbins 

 were extremely fruitful in results. 



A photograph by "Wolf, of Heidelberg, 

 on August 23, 1901, had led to the discov- 

 ery of masses of nebulosity in the vicinity 

 of the new star. A photograph by Ritchey 

 of the Terkes Observatory on September 

 20 confirmed and extended the discovery, 

 showing that the new star was apparently 

 situated in a nebulous mass nearly circular 

 in forih, and of great extent. The photo- 

 graph of this region made by Mr. Perrine 

 with the Crossley Reflector on November 

 7 and 8 when compared with Ritchey 's 

 published photograph of September 20, led 

 to the extraordinary discovery that the 

 well-defined nuclei in the nebula were ap- 



parently in rapid motion; the magnitude 

 of the apparent motion being at least 

 seventy-five times as great as any sidereal 

 motion previously known. Telegraphic 

 announcement of this discovery was made 

 at once, and intense interest was taken in 

 the subject. A photograph made by 

 Ritchey at the Terkes Observatory, on No- 

 vember 9, afforded full and independent 

 confirmation of Mr. Perrine 's remarkable 

 discovery. Photographs made at intervals 

 throughout the winter have enabled us to 

 follow the motions of the brighter masses. 



Later examination of our early photo- 

 graphs of this region, by Mr. Perrine in 

 January, 1902, led to the discovery that 

 two rings of nebulosity surrounding the 

 new star were beautifully recorded on the 

 plate of March 29. "We were thus able to 

 extend the history of the phenomenon back- 

 ward five months. 



The nature of the phenomenon is a 

 mooted question. The favorite theory is 

 that invisible masses of nebulosity existed 

 in this region previous to the formation of 

 the new star; and that the great wave of 

 light, sent out when the brightness of the 

 star was at a maximum, was sufficient to 

 illuminate the dark masses and make them 

 visible to us by reflected light. Bearing 

 upon this question, Mr. Perrine secured 

 valuable polariscopic evidences. A photo- 

 graph of the nebula was obtained after 

 passing the light through a double-image 

 prism, placed at a short distance in front of 

 the plate holder in the Crossley Reflector. 

 Two images of each of the principal nuclei 

 were recorded in such a way as to make 

 it certain that the polarization effects to 

 be expected from reflected light are entirely 

 absent. 



The consensus of opinion is that the new 

 star is the result of a violent collision be- 

 tween two dark stars, or between a dark 

 star and a nebula. It. can easily be shown 

 that the kinetic energy of two such bodies. 



