Flight of Telescopic Meteors seen by W. R. Brooks, Nov. 28, 1883.
Telescopic Meteors.—Observers who are engaged in seeking for comets or studying variable stars employ low powers and large fields, and during the progress of their work notice a considerable number of small meteors. At some periods these bodies are more plentiful than at others, and appear in such rapid succession that the observer’s attention is distracted from the special work he is pursuing to watch them more narrowly and record their numbers. Schmidt saw 146 telescopic meteors during ten years. They ranged between the 7th and 11th mags. Winnecke in the year 1854 noticed 105 of these objects on thirty-two evenings of observation with a 3-inch finder, power 15, and field of 3°. I have also remarked many of these objects when using the comet-eyepieces of my 10-inch reflector[51], and find they are apparently more numerous than the ordinary naked-eye meteors in the proportion of 22 to 1. It would be supposed from the great rapidity with which the latter shoot across the firmament that the smaller telescopic meteors are scarcely distinguishable by their motion, as they must dart through the field instantaneously and only be perceptible as lines of light. But this impression is altogether inconsistent with the appearances observed. They possess no such velocity, but usually move with extreme slowness, and not unfrequently the whole of the path is comprised within the same field of view. The eye is enabled to follow them as they leisurely traverse their courses, and to note peculiarities of aspect. Of course, there are considerable differences of speed observed, but as a rule the rate is decidedly slow and far less than that shown by naked-eye meteors. I believe that telescopic meteors are situated at great heights in the atmosphere, and that their diminutive size and slowness of movement are due to their remoteness. This conclusion will hardly be avoided by anyone who attentively studies the several classes of meteors in their various aspects. Unfortunately no attempt appears to have been hitherto made to determine the actual heights of telescopic meteors, owing to the difficulty of obtaining two reliable observations of the same object. The only way of securing such data would be for several observers to watch certain selected regions by prearrangement either with a low-power telescope or field-glass, and record the exact times and paths of the meteors seen. On a comparison of the results a good double observation of the same object might be found, in which case the real path could be readily computed.
Future observers should note the different forms of telescopic meteors. Safarik has divided them into four classes, viz.:—(1) Well-defined star-like objects of very small size; (2) Large luminous bodies of some minutes of arc in diameter; (3) Well-defined disks of a very perceptible diameter brighter at the border than at the centre, which gives them the aspect of hollow transparent shells; and (4) faint diffused masses of irregular shape, considerable size, and different colours. He has seen hundreds of meteors of every magnitude from the 2nd down to the 12th pass through the field of his 6½-inch reflector (ordinary power 32, field 54′). On Aug. 30, 1880, 9h to 15h he observed between 50 and 100 telescopic meteors, and many others were seen on the following night. Whenever a shower of these bodies, such as that witnessed by Brooks on Nov. 28, 1883, occurs, observers should notice whether the objects participate in a common direction of motion; because, if so, the radiant-point will admit of determination. The horary rate of their apparition ought also to be ascertained. Those who habitually search for comets should invariably make a note of telescopic meteors, as such records would aid inquiries into the relative frequency of these phenomena.
Meteor Showers.—The following short list includes the principal displays of the year:—
| Name of Shower. | Duration | Date of Max. | Radiant- Point. | Sun’s Longitude. |
|---|---|---|---|---|
| α δ ° ° | ° | |||
| Quadrantids | Dec. 28-Jan. 4 | Jan. 2 | 229·8+52·5 | 281·6 |
| Lyrids | April 16-22 | April 20 | 269·7+32·5 | 31·3 |
| η Aquarids | April 30-May 6 | May 6 | 337·6 - 2·1 | 46·3 |
| δ Aquarids | July 23-Aug. 25 | July 28 | 339·4-11·6 | 125·6 |
| Perseids | July 8-Aug. 22 | Aug. 10 | 45·9+56·9 | 138·5 |
| Orionids | Oct. 9-29 | Oct. 18 | 92·1+15·5 | 205·9 |
| Leonids | Nov. 9-17 | Nov. 13 | 150·0+22·9 | 231·5 |
| Andromedes | Nov. 25-30 | Nov. 27 | 25·3+43·8 | 245·8 |
| Geminids | Dec. 1-14 | Dec. 10 | 108·1+32·6 | 259·5 |
Notes.
Quadrantids. Heis was the first to determine this radiant accurately. It was subsequently observed by Masters and Prof. Herschel (1863-4). The radiant is circumpolar in this latitude, but low down during the greater part of the night, hence the display is usually seen to the best advantage on the morning of Jan. 2.
Lyrids. Attention was first drawn to the April meteors by Herrick in the United States. Active displays occurred in 1863 and 1884.
η Aquarids. Further observations are urgently required of this stream. The radiant is only visible for a short time before sunrise. There is a considerable difference between my results and those secured by Lieut.-Col. Tupman, the discoverer of this system in 1870, whose observations place the radiant at 326½—2½ April 29-May 3. These May Aquarids are interesting from the fact that they present an orbital resemblance to Halley’s Comet, which makes a near approach to the Earth on May 4, twelve days before reaching the descending node.
δ Aquarids. The meteoric epoch, July 26-30, was first pointed out by Quetelet many years ago. Biot also found, from the oldest Chinese observations, a general maximum between July 18 and 27 (Humboldt). Showers of Aquarids were remarked by Schmidt, Tupman (1870), and others; but it was not known until my observations in 1878 that the Aquarids formed the special display of the epoch, and that there were many early Perseids visible at the same time.