As soon as the existence of the new orb was confirmed and the fact rendered indisputable, the question naturally arose whether it had ever been seen in former years by the authors of star catalogues, who could hardly have overlooked an object like this though its planetary nature had manifestly escaped detection. It was just perceptible to the naked eye, shining like a star of the sixth magnitude, and ought to have been distinguished by those who had reviewed the heavens with the purpose of determining and mapping the positions of the stars. Reference was, therefore, made to the chief catalogues, when it was found at once that the planet had been unquestionably observed by Tobias Mayer, Le Monnier, Bradley, and Flamsteed. It was several times noted by these observers: by Le Monnier no less than twelve times, and by Flamsteed on six occasions; and it is remarkable that in every instance its true character escaped detection. Neither its special appearance nor its motion attracted attention, so that it was merely catalogued as an ordinary fixed star. Thus Herschel was not anticipated in his discovery. It remained for him, in 1781, to note its exceptional aspect, and to specify it as an object requiring critical investigation. But the early observations above alluded to served a useful purpose in testing the accuracy of the computed orbit, for without waiting many years to compare the theoretical and observed positions, astronomers had in these old records a reliable series of points through which the previous course of the planet could be traced.
The calculations showed that its mean distance from the sun was some 1,750,000,000 miles, and that a revolution was completed in about eighty-four years. It was also found to be a very large planet, greatly exceeding either Mercury, Venus, the Earth, or Mars, though considerably inferior to either Jupiter or Saturn.
Here, then, was a discovery of the utmost importance, and one of the most salient additions to our knowledge which the telescope had ever achieved. The new planet was now definitely assigned its proper place in the solar system, and was regarded as of equal significance with the old planets. True, the new planet of Herschel could not be compared as regards its visible aspect with the other previously known members of our system, but it was nevertheless an object of equal weight. Its vast distance alone rendered it faint. It formed one of the constituent parts of the solar system, which, though separated by immense intervals of space, are yet coherent by the far-reaching effects of gravitation. There is, indeed, a bond of harmony between the series of planetary orbits, which exhibit a marked degree of regularity in their successive distances from the sun; and though they are not connected by any visible links, they are firmly held together by unseen influences, and their motions are subject to certain laws which have been revealed by centuries of observation.
The question of suitably naming the new planet soon came to the fore. Herschel himself proposed to designate it the "Georgium Sidus," in honor of his patron, George III., just as Galileo had called the satellites of Jupiter the "Medicean stars," after Cosmo de' Medici. But La Place proposed that the planet should be named after its discoverer; and thus it was frequently referred to as "Herschel," and sometimes as "The Herschelian planet." Astronomers on the continent objected to this system of personal nomenclature, and argued that the new body should receive an appellative in accordance with those adopted for the old planets, which had been selected from the heathen mythology. Several names were suggested as suitable (on the basis of this principle), and ultimately the one advanced by Bode received the most favor, and the planet thereafter was called "Uranus."
The varying positions of the new body as observed on successive nights were determined by comparisons with a group of six small stars, termed by Herschel [Greek: alpha, beta, gamma, delta, epsilon] and afterwards formed into a constellation under the designation of "Britannia," though it does not appear that this little asterism is acknowledged as one of our constellations. Its position is about midway between Taurus and Gemini, and the following are the principal stars computed for 1881.0, as given by Mr. Marth:
Star. Magnitude. Right Ascension. Declination.
h. m. s.
alpha 9.0 5 42 6.06 23° 35' 6.7" N.
eta 8.7 5 43 17.82 23 26' 7.2 N.
theta 8.8 5 44 0.99 23 53' 30.8 N.
epsilon 8.8 5 45 40.68 23 34' 46.8 N.
The stars are therefore merely telescopic, and are confined to a small area of space, so that the propriety of adopting the group as a distinct constellation is very questionable. Their positions close to Uranus at the time of its discovery, and the fact that the planet's motion was detected by means of comparisons with them, has given to these stars an historical interest which in future years must often attract the student to their reobservation. But it would be unwise, as forming a bad precedent, to accept a group of stars of this inferior type as meriting to rank among the old constellations, when we have numbers of richer groups, situated on their confines, which first deserve such a distinction. However special or unique the circumstances connected with certain telescopic stars may be, and however necessary it may appear to signalize them by a specific title, we are inclined to question the adoption of such means as likely to exercise a wrong influence, inasmuch as it may hereafter originate further innovations of a similar character, and ultimate complications will be certain to arise.
Soon after the discovery of Uranus it was suspected that the planet was encircled, like Saturn, by a luminous ring, but on subsequent observation this was not confirmed, and no such appendage has ever been revealed in the more perfected instruments of our own times. Indeed, if Uranus displays a peculiarity of constitution in any way analogous to the ring system of Saturn, it must be of the most minute character so as to have thus evaded telescopic scrutiny during a hundred years.
The discovery soon attracted the notice of royalty, and the reigning sovereign, George III., anxious to practically express his appreciation of the valuable labors of Herschel, awarded him a pension of £200 a year and furnished him with a residence at Slough, near Windsor, and the means to erect a gigantic telescope with which he might be enabled to continue his important researches. This instrument consisted of a reflector on the "Front-view" construction, with a speculum 4 feet in diameter and of 40 feet focal length. Upon its completion, Herschel immediately began to observe the region of the new planet with the idea of discovering any satellites which might belong to it, for analogy suggested that it was surrounded by a numerous retinue of such bodies. He was soon successful, for, on the night of January 11, 1787. he saw two minute objects near the planet, which renewed observations revealed to be satellites; and he detected two additional ones in 1790, and two others in 1794, making six in all. But the observations were of extreme difficulty. The path of the planet frequently passed near minute stars, and it became hard to distinguish between them and the suspected satellites. Herschel, however, considered he had obtained conclusive evidence of the existence of six satellites with sidereal periods ranging from 5d. 21h. 25m. to 107d. 16h. 39m., and his means of observation being much superior to those possessed by any of his contemporaries it was impossible to have corroborative testimony.
The matter was thus allowed to rest until the middle of the present century, when Lassell, in the pure sky at Malta, endeavored to reobserve the satellites with a two-foot reflector. This instrument was considered superior to Herschel's telescope; and the atmosphere at this station being decidedly more suitable for such delicate observations than in England, it was removed there for the express purpose of dealing successfully with objects of extreme difficulty. The results were very important. Mr. Lassell became convinced that Uranus had only four satellites, and that if any others existed they remained to be discovered. Two of these were found to be identical with those seen by Herschel in 1787, and now called Titania and Oberon. The other two, Ariel and Umbriel, could not be identified with any of those alleged to have been previously detected by Herschel, so that the inference was that they were new bodies, and that the priority of discovery was due to Mr. Lassell; whence it also followed that the older observations were erroneous, and that in fact Herschel had been entirely mistaken with regard to the four satellites he believed he had detected subsequently to 1787.