ASTRONOMICAL NOTES FOR JANUARY, 1911.

New Zealand Herald, Volume XLVII, Issue 14566, 31 December 1910, Page 5 (Supplement)

ASTRONOMICAL NOTES FOR JANUARY, 1911.

BY S. STTTAKT, BRITISH ASTROXOMICAI. ASSOCIATION". The little planet Mercury will be found before sunrise on the 2nd a little to the north-west of the moon, being about four and a-half degrees due north of her apparent centre at mid-day. In his very eccentric orbit he arrives at his least distance from the sun in space on the sth between 1 and 2 p.m. This nearest of the planets to the sun will be found within less than two degrees to the* northward of one of the most distant, Herschell, on the sth at 2.30 p.m. At 5.49 a.m. on the 6th Mercury will be found 2deg. 50min. to the north of Venus, just after they have both risen in the eastern dawn; but probably the sky will be too light and too cloudy to enable us to see them, as both are very near to the sunrise. At 9.30 p.m. on the 10th Mercury will be in the same point of the ecliptic as the sun, and nearly in a right line between the sun and the earth, in what is known as his inferior conjunction. His greatest distance from the ecliptic to the northward, or his maximum heliocentric latitude, is reached on the 15th at Bh. 30m. p.m. On the 15th ho rises at 4.19 a.m., the sun rising half an hour later. After moving retrograde during the time he is about his inferior conjunction, Mercury becomes direct about midnight on the 21st, and. then again moves forward in the ecliptic, through which he moves at present from the 26th degree of Capricorn backwards to the 11th degree, and then forward to the 15th degree, with latitude -from the first degree N. to the fourth, and then back again to the second. On the 28th, about 6 p.m., Mercury will again be found due north of ti.e apparent centre of the moon by about five degrees,

This month should again give :ts Venus is the evening star, as she will set on he 15th at 8.7 p.m. Observers may, herefore, be on the look-out all the month just after sunfset, to see a very brilliant object in the north-western sky and close to the horizon, which will be Hesperus, as the Greeks called Venue in this position. On the evening of the 6th she will be close to Herschell, and some 41 minutes of declination to the south-east of his place, or about three-fourths of the apparent diameter of the moon. She is at the aphelion, or greatest distance from the sun in space, on the 7th about midnight, and at her greatest distance south of the ecliptic as seen from the sun on the 30th between 5 and 6 p.m. In the evening of the 31st Venus will be found some distance to the north-west of the moon.

Mars is gradually increasing his distance to the westward of the sun, rising on the 15th at 2h. 17m. a.m., so that he might be visible under favourable circumstances and the easiest way to look for him is when he is near the moon. This occurs on the morning of the 27th, when he will be found some little distance to the northeast of her apparent po.sition, and easily recognised by his red colour; but, owing to his great distance from the earth, he is at present a very small object to the eye. He is now moving between the 9th and 30th degrees of the sign Sagittarius-, and from the ecliptic to 20 minutes of latitude to the south of it. Jupiter is gradually coming more easily within reach of the observer, f.'nce he rises on the 15th at 21 minutes after midnight, and is pursuing a course between the 10th and 14th degrees of the sign Scorpio, in the second degree of south latitude. On the 23rd he makes a nearly central conjunction with the moon, which consequently will be an occultation ; but, owing -to the fact that both luminaries will then be far below our horizon, we shall see nothing of it. On the evening of that day Jupiter will rise just before the moon, and nearly due west of her centre. '

Saturn remains at present the most conspicuous of the planets to us, if he can be called conspicuous who only shines like a first-magnitude star or less, and is generally taken for one by the inexperienced He is now pursuing a course from the last degree of Aries to the first of Taurus, in the third degree of south latitude, setting on the 15th at llh. 53m. p.m., so that he is easily seen all the evenings. About 4h. 30m. on the 3rd he ceases his late retrograde motion, becomes stationary, and then move forward in the ecliptic. On the evening of the 9th he will bo situated about four degrees south-west of the moon, and will be easily recognisable in that position. On the 21st, between three and four p.m., Saturn will have reached what the astrologers used to call his eastern Oriental quadrature to the sun*

when he is 90 degrees of the ecliptic on the east of our luminary, or passes the meridian on the average about six p.m. He is at present situated among the stars of Pisces and Aries.

The distant planet Herschell is now setting with the sun or near it, so that he is invisible to us, and for this month is confined to the 25th, 26th, and 27th degrees of the sign Capricorn, with half a degree of south latitude. About 8 a.m. on the 2nd he will be some 3 2 degrees to the northward of the moon, and again so about 7 p.m. on the 29th. Nearly at midnight on the 16th he will be in conjunction with the sun, which occurs but once a year. The still more remote Neptune is in the opposite quarter of the heavens to Herschell, as he rises on the 15th at 7 p.m., and is consequently in an excellent position for teiescopists who have instruments of sufficient power. He reaches the opposite place to the sun on the 11th about midnight, and on the 15th about 3 a.m. is situated between three and four degrees north of the moon. This planet, like all the other superiors when about their oppositions to the sun, is now moving retrograde, and between the 21st and 20th degrees of the sign Cancer, two-thirds of a degree on the south of the ecliptic.

The earth is now near its least distance from the sun, the actual perigee of the sun occurring on the 4th between two and three o'clock a.m. The sun, having passed the solstice by a month, will enter the zodiacal sign Aquarius on the 21st at 3h. 23m. p.m. This month the difference between our local clocks and time from a dial will be within four seconds of each other on the 15th, as at solar mid-day the clocks should then indicate in Auck'and XI. 59m. 565. On the Ist the clock shows XI. 54m. Is., and on the 30th XII.h. 4m. 15s. The day on the Ist has a duration of 14h. 36m., while on the 15th it will be 14h. 22m., and on the 30th 13h. 58m., so that, although imperceptibly to most of us, the days are already shortening, although our evenings seem so long. Those who take an interest in the course of the moon may note that her first quarter occurs on the Bth at sh. 50m. p.m., and she is full on the 15th at, 9h. 56m. a.m., being then situated in the £4th degree of the sign Cancer. Owing to the eccentric nature of her orbit, which alternately places he;' before arid behind her average daily positions at intervals of a fortnight, we have almost exactly 14 days between the first and last quarters this month, as the last quarter occurs on the 22nd at sh. 51m. p.m. The new moon occurs on the 30th at 9h. 15m. p.m., in the 10«:h degree of Aquarius. Those who may care to amuse themselves in their leisure time by a few calculations may do so by adding 29d. 12h. 44m. to the times above given, or the half or quarter of this period, when they will find that only on the Bth and 22nd will the results agree; for to make them do so on the whole of the dates it would be necessary to introduce a correction which was not discovered even in ancient Greece, until quite a late period of its history, when probably the period of 414 days was found out, by which a much nearer approximation to the correct, motion of the moon was obtained. This is because the " synodic month," or the time from new moon to new again, .\nd the " anomalistic" period of the moon, or that in which she goes through all her changes of position in regard to her apogee and perigee will in 414 days form a common multiple or cycle which places her at its beginning and end in nearly the same position in regard to tho sun and apogee, but differing in longitude by nearly 49 degrees, or the amount which the sun moves over and above a year, or 360 degrees. This appears to have been among the discoveries of the ancient Chaldeans, if we may judge by what they say of their Saronic cycle, as previously adverted to in these notes.

On the Bth and 22nd there will be low tides, on the 30th high and on the 15th very high; but if the wind is south at the time, not so great as it the wind is strong in the northern quarter.

At nine p.m. on the 15th we- shall l ave near the meridian the stars of Taurus, as the north point will lie nearly bet,ween the Pleiades and Hyades. Far down in the. north will be Capella, and a third of th« way to the meridian the constellation Orion.