The unrivalled constellation of Orion is the stand-out feature of our long December nights which are bracketed by the two brightest planets – Venus as a brilliant evening star, and Jupiter in the pre-dawn. It is a shame that yet another supermoon coincides with the peak of the Geminids meteor shower to swamp what might have been the richest meteor display of the year.
The Geminids arrive between the 8th and 17th and are expected to peak at about 20:00 on the 13th, only four hours before full moon. Under ideal conditions we might have expected to count 100 or more meteors per hour.
Geminids are medium-slow and appear in all parts of the sky, though their paths diverge from a radiant point close to Castor in Gemini which climbs through our E evening sky to pass high in the S at 02:00. Fortunately, a good proportion are bright and the intense moonlight won’t hide them all.
As the diagram in our previous Starwatch indicated, the visibility of both Venus and Mars is improving in our evening sky. Venus’ altitude in the S at sunset improves from about 12° to 22° as it tracks northwards in relation to the Sun. By the year’s end, it sets in the WSW more than four hours after the Sun and brightens from mag –4.2 to –4.3 while its gibbous disc swells from 17 to 22 arcsec if viewed telescopically.
The young earthlit Moon stands above Venus on the 3th and close to Mars on the 5th. The latter, much fainter than Venus, dims from mag 0.6 to 0.9 and, at 6 arcsec, is too small for easy telescopic study. An arrow on our south map shows its motion in Aquarius after the first week of the month.
Our maps show the Plough below the pole in the N as it begins its climb into the NE. Above Orion in the SE is Taurus whose bright star Aldebaran stands to the right of the Moon on the 12-13 December and is occulted by the Moon as seen from the UK later that night as they sink in the W at about 05:25.
Jupiter, rising in the E at about 03:00 on the 1st and by 01:25 on the 31st, climbs through our SE sky to stand some 30° high in the S before dawn. Conspicuous at mag –1.8 to –1.9, it lies above-right of Spica in Virgo and appears 35 arcsec wide when it lies near the Moon on the 22nd and 23rd.
December diary
3rd 13h Moon 6° N of Venus
5th 11h Moon 2.9° N of Mars
7th 09h First quarter
10th 12h Saturn in conjunction with Sun
11th 05h Mercury furthest E of Sun (21°)
13th 05h Moon occults Aldebaran for UK; 20h Peak of Geminids meteor shower
14th 00h Full moon
21st 02h Last quarter; 10:44 Winter solstice
22nd 17h Moon 2.4° N of Jupiter
28th 19h Mercury in inferior conjunction
29th 07h New moon
