Scarcity of names.
The known number of these bodies has accordingly increased so rapidly as to become almost an embarrassment; and in one respect the embarrassment is definite, for it has become quite difficult to find names for the new discoveries. We remember with amusement at the present time that for the early discoveries there was sometimes a controversy (of the same kind as in the case of Uranus) about the exact name which a planet should have. Thus when it was proposed to call No. 12 (discovered in 1850, in London, by Mr. Hind) “Victoria,” there was an outcry by foreign astronomers that by a subterfuge the name of a reigning monarch was again being proposed for a planet, and considerable opposition was manifested, especially in America. But it became clear, as other discoveries were added, that the list of goddesses, or even humbler mythological people, would not be large enough to go round if we were so severely critical, and must sooner or later be supplemented from sources hitherto considered unsuitable; so, ultimately, the opposition to the name Victoria was withdrawn. Later still the restriction to feminine names has been broken through; one planet has been named Endymion, and another, of which we shall presently speak more particularly, has been called Eros. But before passing to him you may care to look at some of the names selected for others:—
| No. | Name. | No. | Name. | |||
| 248 | Lameia | 389 | Industria | |||
| 250 | Bettina | 391 | Ingeborg | |||
| 261 | Prymno | 433 | Eros | |||
| 264 | Libussa | 443 | Photographica | |||
| 296 | Phaëtusa | 457 | Alleghenia | |||
| 340 | Eduarda | 462 | Eriphyla | |||
| 341 | California | 475 | Ocllo | |||
| 350 | Ornamenta | 484 | Pittsburghia | |||
| 357 | Ninina | 503 | Evelyn | |||
| 385 | Ilmatar |
Bettina.In connection with No. 250 there is an interesting little history. In the Observatory for 1885, page 63, appeared the following advertisement:—“Herr Palisa being desirous to raise funds for his intended expedition to observe the Total Solar Eclipse of August 1886, will sell the right of naming the minor planet No. 244 for £50.” The bright idea seems to have struck Herr Palisa, who had already discovered many planets and begun to find difficulties in assigning suitable names, that he might turn his difficulty into a source of profit in a good cause. The offer was not responded to immediately, nor until Herr Palisa had discovered two more planets, Nos. 248 and 250. He found names for two, leaving, however, the last discovered always open for a patron, and on page 142 of the same magazine for 1886 the following note informs us how his patience was ultimately rewarded:—“Minor planet No. 250 has been named ‘Bettina’ by Baron Albert de Rothschild.” I have not heard, however, that this precedent has been followed in other cases, and the ingenuity of discoverers was so much overtaxed towards the end of last century that the naming of their planets fell into arrears. Recently a Commission, which has been established to look after these small bodies generally, issued a notice that unless the naming was accomplished before a certain date it would be ruthlessly taken out of the hands of the negligent discoverers. The provisional letters.Perhaps we may notice, before passing on, the provisional system which was adopted to fill up the interval required for finding a suitable name, and required also for making sure that the planet was in fact a new one, and not merely an old one rediscovered. There was a system of numbering in existence as well as of naming, but it was unadvisable to attach even a number to a planet until it was quite certain that the discovery was new, for otherwise there might be gaps created in what should be a continuous series by spurious discoveries being struck out. Accordingly it was decided to attach at first to the object merely a letter of the alphabet, with the year of discovery, as a provisional name. The alphabet was, however, run through so quickly, and confusion was so likely to ensue if it was merely repeated, that on recommencing it the letter A was prefixed, and the symbols adopted were therefore AA, AB, AC, &c.; after completing the alphabet again, the letter B was prefixed, and so on; and astronomers began to fear that they had before them a monotonous prospect of continually adding new planets, varied by no incident more exciting than starting the alphabet over again after every score.
Fortunately, however, on running through it for the fifth time, an object of particular interest was discovered.Eros. Most of these bodies revolve at a distance from the sun intermediate between that of Mars and that of Jupiter, but the little planet which took the symbol DQ, and afterwards the name of Eros, was found to have a mean distance actually less than that of Mars, and this gave it an extraordinary importance with respect to the great problem of determining the sun’s distance. To explain this importance we must make a small digression.
Transit of Venus.
About the middle of the last century our knowledge of the sun’s distance was very rough, as may be seen from the table on p. 32; but there were in prospect two transits of Venus, in 1874 and 1882, and it was hoped that these would give opportunities of a special kind for the measurement of this important quantity, which lies at the root of all our knowledge of the exact masses and dimensions of not only the sun, but of the planets as well.
Fig. 1.
The method may be briefly summarised thus: An observer in one part of the earth would see Venus cross the disc of the sun along a different path from that seen by another observer, as will be clear from the diagram. If the size of the earth, the distance of the sun, and the relative distance of Venus be known, it can be calculated what this difference in path will be. Now the relative distance of Venus is known with great accuracy, from observing the time of her revolution round the sun; the size of the earth we can measure by a survey; there remains, therefore, only one unknown quantity, the sun’s distance. And since from a knowledge of this we could calculate the difference in path, it is easy to invert the problem, and calculate the sun’s distance from the knowledge of the observed difference in path. Accordingly, observers were to be scattered, not merely to two, but to many stations over the face of the earth, to observe the exact path taken by Venus in transit over the sun’s disc as seen from their station; and especially to observe the exact times of beginning and ending of the transit; and, by comparison of their results, it was hoped to determine this very important quantity, the sun’s distance. It was known from previous experience that there were certain difficulties in observing very exactly the beginning and end of the transit.The “Black Drop.” There was an appearance called the “Black Drop,” which had caused trouble on previous occasions; an appearance as though the round black spot which can be seen when Venus has advanced some distance over the sun’s disc was reluctant to make the entry and clung to the edge or “limb” of the sun as it is called, somewhat as a drop of ink clings to a pen which is slowly withdrawn from an inkpot. Similarly, at the end of the transit or egress, instead of approaching the limb steadily the planet seems at the last moment to burst out towards it, rendering the estimation of the exact moment when the transit is over extremely doubtful.