A little ramble through 19th century astronomy - comet Coggia 1874

 Academy Newspaper Saturday July 11^th 1874

 

The comet discovered by Coggia on April 13 1874 has during the last fortnight rapidly increased in brightness and is now a conspicuous object in the northern sky. It will continue to get brighter, but unfortunately its motion is directly away from the pole, and as it is now beginning to move south rapidly, it will soon get below the northern horizon, so that probably it will not be visible to the naked eye, in the northern hemisphere at least, after July 15, when it will be nearly as bright as a first magnitude star, though very low down.

 It is possible, however, that its tail may be seen after the head has set, as was the case with the famous comet of 1843, Mr. Hind, who has devoted much attention to the present comet, considers that it may be seen in full daylight south of the sun with a powerful telescope about July 22, when it makes its nearest approach to the earth. The circumstance that the apparent path of this comet passes nearly through the sun’s place, coupled with Its very slow motion at first, has made it very difficult to compute its orbit; but theory and observation now agree well, and if observatories in the Southern hemisphere watch it carefully, no less than 200° of its orbit will be fixed, and we can then determine whether it is likely ever to visit us again.

The striking feature of this comet in the telescope is its remarkably bright planetary nucleus, from each side of which a fan of light shoots out transverse to the tail. The spectrum of this nucleus, as found by M. Royet (since confirmed by Mr. Lockyer and at Greenwich), is continuous, indicating a glowing solid or liquid, and therefore supporting the theory that it is a meteor stream. The coma and tail which form the usual parabolic envelope give the characteristic spectrum of carbon consisting of three bright nebulous bands, but what is the form under which the carbon exists remains an interesting question which it is to be hoped that Mr. Huggins will resolve. The tail shows strong radial polarisation.

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