The Discovery of Uranus

Author: William Herschel

The Discovery of Uranus

William Herschel

ACCOUNT OF A COMET

On Tuesday, the 13th of March, 1781, between 10 and 11 in the evening, while examining the small stars in the neighborhood of H Geminorum, I perceived one that appeared visibly larger than the rest: being struck with its uncommon magnitude, I compared it to H Geminorum and the small star in the quartile between Auriga and Gemini, and finding it so much larger than either of them, suspected it to be a comet. I was then engaged in a series of observations on the parallax of the fixed stars, which I hope soon to have the honour of laying before the R. S.; and those observations requiring very high powers, I had ready at hand several magnifiers of 227, 460, 932, 1536, 2010, etc., all of which I have successfully used on that occasion. The power I had on when I first saw the comet was 227. From experience I knew that the diameters of the fixed stars are not proportionally magnified with higher powers, as the planets are; I therefore now put on the powers of 460 and 932, and found the diameter of the comet increased in proportion to the power, as it ought to be, on a supposition of its not being a fixed star, while the diameters of the stars to which I compared it, were not increased in the same ratio. Also, that the comet being magnified much beyond what its light would admit of, appeared hazy and ill-defined with these great powers, while the stars preserved that lustre and distinctness which from many thousand observations I knew they would retain. The sequel has shown that my surmises were well rounded, this proving to be the comet we have lately observed.

Mr. H. reduced all his observations on this comet to three tables. The first contains the measures of the gradual increase of the comet’s diameter. The micrometers he used, when every circumstance is favourable will measure extremely small angles, such as do not exceed a few seconds, true to 6, 8, or 10 thirds at most; and in the worst situations true to 20 or 30 thirds; he therefore gave the measures of the comet’s diameter in seconds and thirds. The first table, containing the measures of the comet’s diameter, shows that, from March 17 to April 18, the apparent diameter had increased from 2" 53"’ to 5’ 20"’.

The second table contains the comet’s distances from several telescopic fixed stars from March 13 till April 19, and those distances expressed in minutes, seconds and thirds. And the third table contains the comet’s angle of position with regard to the parallel of declination of the same stars measured by a micrometer; by which means its places and apparent path might be determined.—Trans. Roy. Phil. Soc.

ON THE NAME OF THE NEW PLANET

By the observations of the most eminent astronomers in Europe it appears that the new star, which I had the honour of pointing out to them in March, 1781, is a primary planet of our solar system.a  A body so nearly related to us by its similar condition and situation, in the unbounded expanse of the starry heavens, must often be the subject of conversation, not only of astronomers, but of every lover of science in general. This consideration, then, makes it necessary to give it a name, by which it may be distinguished from the rest of the planets and fixed stars. In the fabulous ages of ancient times the appellations of Mercury, Venus, Mars, Jupiter, and Saturn, were given to the planets, as being the names of their principal heroes and divinities. In the present more philosophical era, it would hardly be allowable to have recourse to the same method, and call on Juno, Apollo, Pallas or Minerva, for a name to our new heavenly body. The first consideration in any particular event, or remarkable incident, seems to be its chronology; if in any future age it should be asked, when this last-found planet was discovered it would be a very satisfactory answer to say, "In the reign of King George the Third." As a philosopher, then, the name of Georgium Sidus presents itself to me, as an appellation which will conveniently convey the information of the time and country where and when it was brought to view.

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Chicago: William Herschel, The Discovery of Uranus in The Library of Original Sources, ed. Oliver J. Thatcher (Milwaukee, WI: University Research Extension Co., 1907), 335–336. Original Sources, accessed February 21, 2024, http://originalsources.com/Document.aspx?DocID=2MKEXXV67JBIVU3.

MLA: Herschel, William. The Discovery of Uranus, in The Library of Original Sources, edited by Oliver J. Thatcher, Vol. 6, Milwaukee, WI, University Research Extension Co., 1907, pp. 335–336. Original Sources. 21 Feb. 2024. http://originalsources.com/Document.aspx?DocID=2MKEXXV67JBIVU3.

Harvard: Herschel, W, The Discovery of Uranus. cited in 1907, The Library of Original Sources, ed. , University Research Extension Co., Milwaukee, WI, pp.335–336. Original Sources, retrieved 21 February 2024, from http://originalsources.com/Document.aspx?DocID=2MKEXXV67JBIVU3.