The Night Sky in January

Abstract

DURING this month, the night shortens in the latitude of London by 1 hour 10 minutes, reckoning from sunset to sunrise. The moon is new on January 9, and full on January 24. Occultations of stars by the moon include three stars of magnitude 3–4 of the Hyades cluster which precedes Aldebaran. The disappearances as seen from Greenwich take place on January 20 as follows: δ Tauri at 21h. 37·9m. at position angle 107° from the north point of the moon's disk: 64 Tauri at 22h. 31·1m. at 142° and 68 Tauri at 23h. 29·0m. at 16°. On January 23, λ Geminorum (3·6 m.) is occulted at 20h. 20·9m. at 121°. There is a fine array of planets in the evening sky—Venus, Mars, Jupiter and Saturn—whilst Uranus, a faint 6th magnitude object, is in Aries near the 6th magnitude star 53 Ariotis. At the beginning of the month, Mars is overtaking Jupiter in the eastward shift of the two planets among the stars by about ½° a day, and on January 7 at 15h. there is a conjunction, the geocentric distance between the two objects being 1·2°. It is interesting to compare the colours and magnitudes of Mars and Jupiter when close together. Lunar conjunctions with the planets occur as follows: Jan. 8d. l0h. with Mercury; 12d. 13h. with Venus; 15d. 22h. with Jupiter; 16d. 7h. with Mars; 17d. 17h. with Saturn. In mid-January at about 22h., the southern meridian is bright with the stars of Taurus, Auriga, Orion, Gemini, Canis Minor and Canis Major. The Great Nebula of Orion shows to the naked eyo as a hazy patch. The photographic plate is required to show the nebulosities, which, enveloping the Pleiades, are but the central condensation, according to Barnard, of an enormous nebula covering at least 100 square degrees. Not far from φ Tauri is a dark nebulous region giving the strongest proof, according to the same authority, of the existence of obscuring matter in space. Near ζ Tauri is the so-called Crab Nebula, which is No. 1 in the catalogue of 103 nobulæ drawn up in 1781 by Messier for his own use when searching for and identifying comets.