THE NEBULA OF ORION, 261 



stars from the first to the seventh magnitude, inclusive, falling within 

 ^:" of each other if the stars were fortuitously scattered over the whole 

 lieavens to begin with. And, further, he has shown that the chances 

 are 170,000 to one against any such stars, if fortuitously scattered, 

 falling within 32" of a third so as to form a triple star. The chances 

 against any such grouping as that seen in the trapezium of Orion are 

 enormously greater than the numbers given above, and the inference is 

 irresistible that these stars are in some way physically connected. 

 We shall see, too, that it is also probable that these stars are in some 

 unknown way related to the surrounding nebula. 



4 



Fig. 3. 



Central and most brilliant portion op the Great Nebula in the Sword-handle op 

 Orion, as observed by Sir John Herschel in his 20-foot Reflector at Feldhauben, 

 Cape of Good Hope (1834 to 1837). 



In 1811 Sir William Herschel was led to suspect changes in the 

 form and brightness itself: an inference which he probably drew from 

 a comparison of the early drawings with the appearance of the nebula 

 as he saw it in his own reflectors ; and in 1824 the younger Herschel 

 made a drawing of the nebula and the stars immersed in it, as shown 

 by his 20-foot reflector. 



This drawing and a description of the nebula are given in " Me- 

 moirs of the Royal Astronomical Society," vol. ii., p. 489, and a copy 

 of the drawing, so far as the small stars immediately about the tra- 

 pezium are concerned, is given in Fig. 4. 



The recession of the nebula from the stars of the trapezium is here 



