Periodical Comets Due in 1890.

Te Aroha News, Volume VII, Issue 445, 12 February 1890, Page 3

Periodical Comets Due in 1890.

Of the four periodical comets which are expected to return next year, two are of well established periods, and have been seen on several occasions; the other two have each been observed at one return, with a probability that it was seen on an occasion several revolutions earlier. Brorsen’s was discovered at Kiel on the 26th of February, 1846. Its period is about five and a half years, and it was subsequently observed at returns in 1857, 1868, 1873, and 1879. Another will be due early in . 1890. D’Arrest’s was discovered at Leipzig on the 28th of June, 1851; it has a period of six and a-half years, and was observed in 1857-8, in 1870, and in 1877. It escaped observation in the winter of 1883, but another return will be due next summer. M. Coggia discovered a small comet at Marseilles on the 10th November, 1873. The investigation of Professor Weiss made it probable that this was identical with one detected by Pons on the 23rd February, 1818, but, though its period is probably about five and a-half years in duration, it has not been seen since 1873. Returns, if that be the true period, were due in 1879 and 1884; and .another will be expected to take place early in 1890. Mr Denningdiscovered a cometat Bristol on the 4th of October, 1881. This has been thought to be identical with the comet found by M. Blanpain on the 28th of November, 1819. The last determination, says Mr T. Lynn in Knowledge, of the orbit of Denning’s comet is that of Mr W. E. Plummer, published in No. 25 of Copernicus , which makes its period 3,235 days, or about 8-8 years, so that as the perihelion passage in 1881 took place on the 13th of September, the next will be due soon after midsummer, 1890. Professor Winnecke suggested that Denning’s comet might be identical with one seen (once only) by Goldschmidt on the 16th of May, 1855, and which was also thought to have been identical with the lost comet of De Vico. But as Goldschmidt could only obtain one approximate position, neither of these conjectures admits of proof.