December Skies 2005

Several remarkable solar system and stellar sights are visible in our December skies.  Long nights combine with Winter’s prominent stars and constellations for convenient viewing in the evening and before dawn in the morning. However, the Geminid Meteor Shower, typically Arizona’s finest, will be less brilliant this year due to the bright Moon on shower dates.

December brings the holidays. This would be an excellent opportunity to receive a gift of (or treat oneself to) a quality pair of binoculars to help navigate the night sky!

The Sun:  In December the Sun reaches its lowest noontime altitude above the southern horizon for the entire year.  The Sun begins December in the constellation of OPHIUCHUS, and remains there until December 18th, when it enters SAGITTARIUS.

The Moon:
There are two NEW MOONS in December: On the 1st in SCORPIO & on the 30th in Sagittarius.
The 1st QUARTER MOON occurs on December 8th in AQUARIUS.
December’s FULL MOON occurs on the 15th of the month in TAURUS.
The 3rd QUARTER Moon occurs late on December 23rd in VIRGO.

In December the Moon passes all five naked-eye Planets:
VENUS: in SAGITTARIUS the evening of December 4th.
MARS: very close to the Moon in ARIES overnight the 11th – 12th.
SATURN: close to Saturn in CANCER during the night of the 18th – 19th.
JUPITER: fairly far from the crescent Moon in LIBRA the mornings of the 26th & 27th.
MERCURY: rises with a very thin crescent Moon about 6:30a.m. (1 hour before sunrise) on the 29th in Ophiuchus.

The Moon can be seen near these Bright Stars:
Waxing crescent Moon in the “teapot” handle in Sagittarius the evening of the 3rdth.
Waning gibbous Moon near Castor & Pollux in Gemini the evening of the 17th.
Waning gibbous Moon near Regulus in Leo the evening of the 20th.
Waning crescent Moon very near Spica in Virgo at dawn on Chrustmas morning.
(The Moon eclipses Spica for observers north of approximately Salt Lake City.)

The Evening Sky:
The Sun: :  December’s earliest sunsets of the year occur at about 5:15p.m. throughout the first half of the month. By month end, sunset still occurs only 10 minutes later (at 5:25p.m.)!

Evening Planets: VENUS, MARS and SATURN.
Venus, the brightest night sky object after the Moon, begins the month in Sagittarius, and moves into CAPRICORNUS on the 13th. Through a telescope, Venus appears as a brilliant white (and large) crescent. As Venus catches up with the Earth in its orbit, Venus grows in apparent size but shrinks into a thinner crescent all month. Venus starts the month 32% illuminated (a fat crescent); at month’s end the planet is a 6% illuminated, very thin crescent.  During December, the planet speeds toward the Sun enroute to becoming a morning planet in January: Venus sets 3 hours after the Sun on December 1st, but only 1 hour after sunset on December 31st.

Look for the Moon a bit to the left of Venus the evening of December 4th.

Mars in December lags behind the Earth and shrinks in apparent size. Nevertheless, Mars offers excellent viewing all month. Small telescopes will show the planet as a round orange disk. Telescopes of at least 4-inches diameter will show the darker regions (volcanic areas) on the planet’s surface.

Try to visit a Public Star Party early in the month (see below) to enjoy spectacular views of the red planet.  Later in the month Mars will appear much smaller than it does in early December.

Saturn, in CANCER the Zodiac crab, rises about 9:45p.m. on the 1st and about 2 hours earlier on the 31st.  Telescopic observers will easily notice Saturn’s prominent ring system and several of its brighter moons.

The Morning Sky
The Sun:  Sunrise in Central Arizona occurs about 7:15a.m. on December 1st, but as late as 7:35a.m. on the 31st.  Our early sunsets and late sunrises make December’s days the shortest of the year.

The Moon: The waning MOON is best seen in the morning sky between the 13th and the 29th of the month.

Morning Planets: MERCURY & JUPITER.
Mercury brightens all month as it moves away from the Sun in the morning sky. However, it still remains fairly close to the Sun and will be much easier to spot through binoculars.
Mercury begins December in Libra, moves Westward into Scorpio on the 14th, and on into Ophiuchus on December 18th.  It rises more than an hour before the Sun from the 1st through the 24th of the month, but is highest above the horizon between the 5th and 15th. Scan the Southeastern sky about 1 hour before sunrise to spot the elusive and speedy orange planet.

Jupiter, in LIBRA all month, is far enough ahead of the Sun to be an easy observing target.  It rises at about 4:45a.m. on the 1st of December and at about 3:15a.m. on the 31st. Telescopic observers will enjoy watching Jupiter’s magnificent cloud bands and four bright moons orbiting the planet. Between December 3rd and the 8th telescopic observers can observe Jupiter slowly pass two 6th magnitude stars.

What Else to See?  Observers with binoculars or small telescopes may view the Moon occult (pass in front of) or graze (pass very near to) several stars of 6th magnitude or brighter between December 5th and 18th. A listing of these events may be found here.

December is the last month for convenient evening viewing of the “Summer Triangle” Milky Way constellations of CYGNUS, LYRA, and AQUILA.  These stars set in the West-Northwest in December as the wWinter Milky Way takes center stage.

Binoculars or a small telescope will add to the pleasure of viewing the many prominent Winter sky objects.  Be sure to check out Venus, Mars, the Pleiades star cluster in Taurus, the Orion Nebula (in the center of Orion’s sword). Later in the evening, the winter Milky Way and several prominent nebulae and star clusters will be higher in the sky in ORION, GEMINI, CASSIOPEIA, PERSEUS (including the famous “Double Cluster”), and AURIGA.

Free Public Star Parties held during December offer public viewing of many astronomical objects of interest, including Mars, the Moon and Saturn!

Visit the East Valley Astronomy Club on Friday, Dec. 9th for stargazing in Gilbert (see the EVAC website below).

Join the Phoenix Astronomical Society on Thursday evening, December 8th for an evening of stargazing at Paradise Valley Community College (see the PAS website below).

Good Luck Observing!