Page:Popular Science Monthly Volume 89.djvu/107

 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

�� �