Popular Science Monllih/ 



93 



Infra-red Yellow Violet Ultra-vioiCL 



Photographs of Saturn made by Professor Wood with various rays, showing how much 



more is revealed by some rays than others 



by means of infra-red, yellow, violet 

 and ultra-violet light. 



Both Saturn and Jupiter are striped 

 with belts which have been the subject 

 of much discussion among astronomers. 

 Study the accompanying photographs 

 and you will see how different is the 

 aspect of the planets when photographed 

 with different rays, whether visible 

 yellow or invisible infra-red or ultra- 

 violet. The belts on the ball of each 

 planet, which can be seen with the eye 

 in a telescope and which are very dis- 

 tinct on photographs made with visible 

 yellow rays, vanish almost complete- 

 ly when photographed with infra-red 

 rays. When ultra-\iolet light is used 

 a remarkable transformation of the 

 planets occurs. A broad dark equatorial 

 belt surrounds each planet, and a large 

 dark polar cap appears. This equatorial 

 portion is the brightest part of each 

 planet when photographed with visible 

 yellow light. When ultra-violet is 

 employed the bright belts vanish. The 

 equatorial dark belts are still recorded, 

 but they are slightly narrower than when 

 photographed in violet light. Moreover 

 the dark polar cap has decreased in size. 



Variations in the intensity of the 

 inner and outer ring of Saturn are also 

 shown in the different "photographs. 

 The surface features of both Saturn and 

 Jupiter have been repeatedly photo- 

 graphed, but not with the result of 



adding much to our knowledge. At 

 last we have a method which may 

 enable the astronomer to interpret the 

 puzzling belts intelligently. It is much 

 too early to venture an opinion. Much 

 work remains to be done with the 

 spectroscope. Perhaps it may turn out 

 that the bands of Saturn may be due 

 to some substance which has not been 

 made in any earthly laboratory or to 

 some substance, which has never been 

 studied in layers thick enough to bring 

 out the characteristic appearance. It 

 is also possible, though hardly probable, 

 that the belt is due to a fine mist or dust 

 which absorbs violet light; but it seems 

 unlikely that such a mist would appear 

 dark for the simple reason that it would 

 reflect equally as much light as it ab- 

 sorbed. As a venture we might attri- 

 bute the belt to chlorine gas, which 

 absorbs violet and ultra-\iolct light pow- 

 erfully and is transparent to yellow light. 

 When we recall the enormous quantity 

 of chlorine locked up in the salt of the 

 ocean it is perhaps possible that laige 

 quantities may exist free in the atmos- 

 phere of young planets like Jupiter and 

 Saturn. 



It seems highly probable that extreme- 

 ly valuable results may be obtained if 

 these methods are applied to the planet 

 Mars. Unfortunately, at this time Mars 

 is too far away, and the photographs 

 which I made show nothing of interest. 



Infra-red Yellow Violet Ultra violet 



Photographs of Jupiter made by Professor Wood with different rays 



