The Parents' Review
A Monthly Magazine of Home-Training and Culture
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The Evening Sky--November, 1890.
Last quarter, 4th; new, 12th; first quarter, 19th; full, 26th.
On November 26th a partial eclipse of the Moon occurs, but we see nothing of it, our satellite being below the horizon at the time, 1 p.m. The inhabitants of the islands in the West Pacific and of China will be able to observe it, weather permitting.
On the 18th is an occultation of 33 Capricornus, from 4.42 to 5.35 p.m., and on the 24th, 38 Arietis, of the 5th magnitude, approaches very near the Moon at 7.25 p.m.
Venus is an evening star in Scorpio, setting at the beginning of the month at 5.27, and at the end at 4.18.
Mars is in Capricornus, rapidly traveling eastward, and on the 13th overtakes Jupiter, they then being in conjunction (or on the same meridian). Mars is south of Jupiter on November 1st.
Mars sets at 9.11, half-an-hour earlier than Jupiter, but on November 30th he sets at 9.18, about forty minutes later.
Saturn is the bright star visible in the south at eight o'clock in the morning.
Neptune can be well observed this month, and is the only planet which finds a place on the map.
Camelopardus is a wide-spread, but obscure, and difficult to distinguish with the naked eye. It contains a nebula, consisting of a bright ring, with a star of the 14th magnitude in the central darkness.
Perseus is on the meridian and overhead. This is a brilliant constellation, situated in the Milky Way, east of Cassiopeia, but further from the Pole. It can easily be recognised by a row of bright stars along the Mile Way. Perseus is represented in the picture-maps as holding in his left hand the head of Medusa, in which is the variable star named Algol, while his uplifted right hands clasps a spear, with which he is ready to destroy the dragon ready to attack Andromeda.
Algol is a variable star of short period, and its difference in brilliancy can easily be perceived, as the whole time occupied by a cycle of its changes is only two days, twenty hours, fifty minutes. It is generally of the 2nd magnitude, where it remains for two days, thirteen hours. This variability of brightness was discovered in 1669, and has been observed ever since. The cause of it is unknown, although, of course, theories have been put forward to account for it. One is the the diminution of light is caused by the interposition of a large satellite; another, that the star itself has periods, similar to our sun-spot periods.
Triangulum is a small constellation between Andromeda and the Pleiades, and south of Perseus. It contains a very large faint nebula, evidently spiral in form.
Aries lies south of Triangulum, and has only three bright stars to distinguish it by, although the constellation extends some way further east into an apparently dull region, which, however, contains several double and quadruple stars when viewed through a telescope. Spring commences when the sun enters Aries, and consequently it is on the meridian at midnight at the autumnal equinox.
Eridanus is on the meridian, and lies south-east of Cetus. It contains what Lassell describes as the most interesting and extraordinary object of the kind he had ever seen:--An 11th magnitude star in the centre of a circular nebula, itself placed centrally upon a larger and fainter circle of hazy light. The spectroscope tells us this wonderful nebula is not gaseous.
"Our periodic meteors are the debris of ancient but now disintegrated comets, whose matter has become distributed round their orbits." Such is the present theory about those mysterious visitors of ours, which excite at once our admiration and our wonder. The Sun is supposed to influence the nuclei of a comet until it is completely pulverized in course of time. The granules of a nucleus become detached and travel in a swarm, portions of which lag behind and spread themselves out along their path, until at last they form a complete ring as in the case of the August meteors. Those, however, which are visible on November 12 have not yet reached that stage, and the shower of November 27 is of such recent growth as to have been formed since 1852.
On any clear night throughout the year, an occasional shooting star will be seen, for it is well known that meteors innumerable revolve round the Sun. The Earth encounters millions of them daily, and it has been computed that our globe increases in bulk at the rate of 100 tons daily, by the addition of falling stars and aerolites attracted by it.
On the night of November 12 and 13, 1833, there was seen all over America a magnificent display of meteors, which fell so fast, that 240,000 were said to fall in nine hours, although they could not be actually counted. They all seemed to emanate from Leo, in whatever part of the sky that constellation was during the night. Their coming from one radiant point proved that the meteors approached in straight parallel lines, their apparent centrifugal divergence being due to perspective, and these parallel lines must be sections of their orbits round the Sun, intersecting the orbit of the Earth. The Leonids (so called from their radiant point) revolve in 33.27 years, in an ellipse lying between the Earth and Uranus, and the group extends so far that it occupies six or eight years in getting past the point nearest to the Earth's orbit.
Therefore, when the senses part of the swarm is at A, we get a brilliant display, with a minor one for the two or three years previous and subsequent, and when the swarm is at B, we see only a few stragglers. In 1866 another remarkable shower occurred, observed best this time by Europeans. Dense clouds of meteors fell, some equal to Venus in brilliancy; nearly all leaving behind them trains of emerald green or bright blue light; in some instances lasting several minutes. In the same orbit as these meteors moves a comet, known as Tempel's comet of 1866, which is expected to return in 1899.
A second distinct shower occurs on November 27th, and this has a most interesting history. To begin at the beginning, we must go back to a comet discovered by an Austrian, named Biela, in 1826, which was found to be periodic, and to have been seen in 1772, and again in 1805. Its period was calculated to be six years and eight months. At its two next returns, the earth was not in a favorable part of its orbit to see the comet, so it was not observed again until 1845, when several astronomers noticed it as usual in November and December. But in the following month (January, 1846), a hitherto unparalleled accident had happened to it; it had divided into two unequal comets and travelled on its way double. During February, the smaller one increased until it was as large as its companion, then it diminished, and in March vanished entirely, although the other one was visible for another month. Imagine the keen interest with which the return of this extraordinary and unique phenomenon was watched for when it became due in 1852! The two comets appeared punctually, but were much further apart than before. They passed out of sight about the end of September, 1852, and have not been seen since. In 1872, our position was very good for observing them, had they continued their previous course, but not a trace of them was visible. Judging from analogy, it was predicted that if the two comets were not seen in 1872, the earth would meet a swarm of meteoroids consisting of their remains, and a shower would be the result, with a point in Andromeda as the radiant point. The prediction was fulfilled. A distinct shower was observed on November 27th, although neither so numerous nor so brilliant as that on the 12th, and the meteors all moved in the direction foretold, whence they obtained the name of Andromedids. One reason why the Andromedids are not so brilliant, is that they travel round the Sun in the same direction as we do, direct, while the Leonids are retrograde in motion, as may be seen in the diagram above. The former overtake us, their rate of progress being under twelve miles a second quicker than ours, but the latter meet us, and our combined motions give a total of forty-four miles a second. In thirteen years Biela's comet (or its present for of Andromedids) travels twice round its orbit, so another display was foretold for 1885, and was observed in Southern Europe, the meteors being larger and more frequent than in 1872, their number being estimated at 75,000 per our. They travelled very slowly for a short way, and disappeared in a confusion of yellowish sparks.
Typed by mlgthompson, Sept 2017
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