Wonders of nature science : an every day book for the student and intellectual observer.

Date:
[1873?]
Catalogue details

Licence: Public Domain Mark

Credit: Wonders of nature science : an every day book for the student and intellectual observer. Source: Wellcome Collection.

    17/596 (page 5)
    light which falls upon it, whereas our Moon reflects only *17 of the light it receives. But Professor Gr. P. Bond assigns a far higher luminosity to Jupiter, insomuch that according to his estimates the planet actually gives out more light than it receives. Another suggestion may be made here. Sun-spots are known to be periodical, their maximum and minimum being about eleven years apart. As Mr. Huggins some years ago observed the equa- torial belt of Jupiter to be of the same ochreish yellow as it is now, there is good reason to suspect periodicity in this change. A period of maximum of Sun-spots is now approaching. Have these two phenomena any relationship to each other ? If so, why should the change in Jupiter be confined to its equator ? Evidently the coloured matter, whatever it may be, is for the most part below the surface of the cloudy envelope, for besides the cumulus clouds which are constantly seen on the southern part of the belt, the whole of the surface is mottled with white markings. These I have attempted to depict in the drawing now engraved, but any such attempt can give but a slight notion of the complexity and beauty of the reality. The white cumulus clouds on the northern (or upper side) of the yellow equatorial belt have been left behind by the rapid rotation of the planet, the surface of which at this part, travels at the rate of nearly 30,000 miles per hour. When a change of colour is in question it might reasonably be anticipated that the spectroscope would afford us valuable informa- tion as to the nature of the change. Mr. Huggins, describing the spectrum of Jupiter in the Philosophical Transactions of the Eoyal Society » for 1864, states that he has discovered several dark lines in the red portion of the spectrum, which do not correspond with any of the Fraiinhofer lines in the solar spectrum. These dark lines in Jupiter's spectrum are probably due to an absorption of some of the solar rays in the planet's atmosphere, taking place both as they enter and leave the cloudy envelope. But, supposing Jupiter to be to any appreciable extent self luminous they may be due to the presence of some elements in the planet which are not present in the Sun ; or these substances may be present m the Sun, and yet not render their presence sensible by absorbtive action. If these elements areTn a state of combustion, dark lines would be produced by a portion of the light they emit being absorbed by their own vapour in the atmosphere of the planet. r In the spectrum of Jupiter seen with a star telescope adapted