A little ramble through 19th century astronomy - Changes observed on Jupiter in 1869 by John Browning

During the months of October and November 1869 the planet Jupiter has presented a spectacle of singular and almost exampled beauty. The belts on the planet are more than usually numerous, and they display a greater variety of colours than I have ever yet seen ascribed to them. The equatorial belt, which has been for years the brightest part of the planet is now not nearly so bright as the light belts to the north and south; usually it has been free from markings, and now it is often covered with markings, which resemble piled up cumulus clouds: it has generally been colourless, shining with a silver grey or pearly lustre – now it is a rich deep yellow, greatly resembling the cloud of electotyped gold.

The woodcut represents Jupiter as it was seen on the night of 9^th October 1869 in a reflecting telescope with a silvered glass mirror of 12.25 inches diameter. The upper part of the planet is the South Pole. On this portion of the disc there are three dark belts, while on the North Pole there are only two.

The poles of the planet are ashy blue, and the darker belts nearest to them present a darker tint of the same colour. The bright belts next, these are pearly white, and shine more brilliantly than any other portion of the planet. The dark belts next to the central bright belts are coppery red. As already mentioned, the central belt, which has been for many years a pearly white, is now a rich golden yellow.

Three of four dark markings on the lower part of the southern dark belt nearest the equator will be seen to incline to the left. If our Earth were removed to Jupiter’s distance, its disc would appear no larger than these dark masses, so enormous is their extent. The rotation of the planet is carrying them towards the right: we may assume that the bright vapour between them is left behind by the planet, which is here travelling at the rate of nearly 3,000 miles per hour.

Spectrum analysis has taught us to respect that any change in the colour of the light proceeding from an object, indicates a change of the object itself. If Jupiter, the largest planet in the solar system has still retained so much heat as to shine partially by its own light, the present considerable change in colour may enable spectroscopist to obtain some information on this interesting subject.

John Browning

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