The Moon stands low in the E at nightfall on 12 December, to the right of Aldebaran in Taurus and below the Pleiades.
As it creeps closer to Aldebaran, a telescope shows it hide several stars in the V-shaped Hyades star cluster on the way. The first is Gamma Tauri, at the point of the V, which winks out at the Moon’s E limb at 21:39 as seen from London and a minute earlier for Edinburgh. Other fainter Hyades stars, all near 153 light years distant, are also occulted before Aldebaran itself slips behind the Moon’s upper limb later in the night.
Aldebaran, the brightest star to be occulted this year, is hidden from 05:24 until 05:53 on the 13th for watchers in London and from 05:26 to 05:41 for Edinburgh. Along a line from Stornoway to Aberdeen, it experiences a grazing occultation, perhaps winking on and off as it slips behind successive mountains at the lunar limb. From N of that line it misses the Moon completely.
Our chart, a variant of one that has appeared here before, depicts the S sky from horizon to overhead at 00:30 at present, but is equally valid for 22:30 in mid-January and 20:30 by mid-February. At its heart is the glorious form of Orion but also present are Canis Major and Sirius, the brightest star in our night sky. Capella in Auriga is conspicuous almost overhead while Aldebaran and the Hyades and Pleiades stand above and right of Orion.
Towards the upper left are Castor and Pollux, the Twins in Gemini, and the radiant for the Geminids meteor shower, due to peak at about 20:00 on the 13th before petering out on the 17th. At its height, in excess of 100 medium-slow meteors per hour might be seen under the best conditions. It is just as well that a good number are bright, for the maximum coincides with the full moon which will swamp the event this year.
It is best to wait a few days for the moonlight to subside before seeking out some of the so-called deep sky objects that are also plotted on the chart
Foremost is the Orion Nebula, also known as Messier 42, or M42. This cloud of gas and dust in which new stars and planets are coalescing glows as a misty patch in Orion’s Sword, hanging below Orion’s Belt. Some 1,350 light years away, it is visible to the naked eye in a good sky and easy through binoculars.
Both the fifth-magnitude M35 in Gemini and the slightly brighter M41, 4° S of Sirius, are clusters of stars at distances of 2,800 light years and 2,300 light years respectively.
If M42 represents star birth then M1, more than 6,000 light years away and near Zeta Tauri, the star at the tip of Taurus’ S horn, marks a star’s death. Known also as the Crab Nebula and dimly visible as a small oval smudge near the ninth magnitude, it is the expanding dusty debris from the disintegration of a massive star in a supernova explosion observed by Chinese astronomers in 1054.
