It is the last month of the year and winter arrives just before Christmas. The evenings are quite cold and it now gets dark so early that almost anyone is more likely to be outside after dark. The cold, dark and dry December skies present some of the best viewing opportunities, so just look up if you happen to be outside after dark. A prepared observer, however, will walk away with an even more enjoyable experience.
This month there are many new constellations to explore, some of them are quite challenging and might only be observable at a dark sky site with a clear southern horizon. Many of the constellations from the past few months are still visible, so this is a good time for a refresher. A planosphere or smartphone app like Google Sky Map can help determine where to look to find each constellation, and a Wikipedia link is provided to further aid in identifying each constellation’s appearance.
Picis Austrinus (Southern fish)
This constellation, located directly south of (below) Aquarius, never rises very high above the southern horizon from our northern hemisphere location. In a light-polluted sky, 1st magnitude Fomualhaut might be the only visible star. This constellation is related to one of the 48 constellations cataloged by 2nd century astronomer Ptolemy.
Sculptor (The sculptor)
This is another southern constellation of dim stars that does not rise very high in the sky. I have never seen it, so I will be sure to look for it during my next visit to a dark sky site. The most notable characteristic of this constellation is that it contains the southern pole of the Milky Way Galaxy. The implication of this is that an observer is looking out of the galactic plane, instead of through its long axis as when observing the Milky Way. This explains why there are fewer stars in this region of the sky. Find this constellation by looking south of Aquarius (from October’s Scope Out and Cetus from November’s Scope Out.
Phoenix (The mythical Phoenix)
Another low, dim southern constellation, located south (below) Sculptor.
Lacerta (The lizard)
This is a northern hemisphere constellation that presents a slight “W” shape, and is hence sometimes referred to as “Little Cassiopeia.” It is located south of Cepheus and north of Pegasus. Cassiopeia and Andromeda are also nearby. Most notable for telescope viewers is Roe 47, a multiple star system consisting of five gravitationally-bound components between 6th and 10th magnitude. While the brightest, 6th magnitude component can usually be seen with the unaided eye under very dark skies, a modest telescope is required to see all five components.
Triangulum (The triangle)
This small northern constellation presents as well-formed triangle of three stars. It is not bright enough to jump out at the observer, but can be seen in all but the most light-polluted skies. Look for it between Perseus, Andromeda, and Pisces.
Aries (The ram)
Aries, one of Ptolemy’s 48 2nd-century constellations, is our zodiacal constellation for this month. It is located on the ecliptic between Pisces and Taurus, and just south of Triangulum. This constellation’s stars are easily seen, but the constellation bears little resemblance to a ram. The most notable aspect of this constellation is that it is on one intersection of the celestial equator and the ecliptic, representing the Sun’s location at Vernal Equinox.
SOLAR SYSTEM OBJECTS
The Sun. The Winter Solstice is December 21st, the longest night and shortest day of 2014. There are a couple of things that can be noted for someone wishing to gain a greater understanding of the Sun’s seasonal movement. On the day of the solstice, note the direction in which the Sun rises and sets, and note how high in the sky the Sun is at noon. Save these observational notes, because we will refer to them again when recording these same points at the equinox in March, and at the Summer Solstice in June. The differences will be astonishing!
|December 5||Among the Hyades|
|December 6||Full Moon|
|December 12-13||Conjunction with Jupiter|
|December 14||Last Quarter|
|December 19||Conjunction with Saturn|
|December 22||New Moon|
|December 22||Conjunction with Venus|
|December 29||First Quarter|
Mercury makes a brief evening appearance late in the month. It will be difficult to spot as it quickly follows the Sun below the horizon. By December the 31st, it can be seen very close to Venus.
Venus begins an evening apparition late in the month that lasts through July 2015. It will be difficult to spot very low on the western horizon after sunset, setting during dusk at first, and then just as it gets completely dark by month’s end. Look for a pretty paring of Venus and a very thin crescent moon on December 22nd.
Mars moves from Sagittarius into Capricornus this month, and will remain low on the western horizon above and to the left of the sunset point.
Jupiter continues to grow larger (telescopically) and brighter, and rise earlier each evening as it progresses toward its next opposition in February. It rises above the eastern horizon at about 10pm in early December, and at about 8pm by late December. It has grown quite large (43 arcminutes) for telescope observers.
Saturn returns as a morning object, rising about an hour before the Sun at the beginning of the month, and about three hours before sunrise by month’s end.
December 13-14 – Geminids Meteor Shower
Look for this meteor shower just before midnight on these two nights. There is a good chance of seeing a hundred or more meteors per hour! The radiant (the apparent point of origin) is in the constellation Gemini, which will be high overhead as midnight approaches. Be sure to get some observing in before the Moon rises at about 11pm and midnight on these two nights.
© 2014 James R. Johnson.