December 2012 Night Sky Calendar
DECEMBER 2012 NIGHT SKY CALENDAR
SUNDAY, DECEMBER 2, 2012
JUPITER AT OPPOSITION
By the time you read this article, this event will have already occurred. However, you'll see Jupiter throughout the night all month. When at opposition, a planet rises around sunset and sets around sunrise. Were we to observe planetary motions from a plane above the solar system, we'd see Earth pass between the Sun and Jupiter today. Of course, were we high enough to view all the planets, they'd appear stationary. However, as we're engaging in mind play, we can be dodgy with the verbs.
TUESDAY, DECEMBER 4, 2012
MERCURY AT GREATEST WESTERN ELONGATION
Mercury is never particularly easy to observe. Being the closest planet to the Sun, Mercury remains close to Sol in our sky. However, when it strays far enough away, at configurations called "elongations," observers often have a better opportunity to find it. Mercury is at greatest western elongation today and will be approximately 20 degrees from the Sun. When at western elongation, Mercury will be visible in the eastern pre-dawn sky. (When at eastern elongation, Mercury is in the western evening sky.)
See the MERCURY section of planet watch for more information about the first world.
WEDNESDAY, DECEMBER 5, 2012
LAST QUARTER MOON
THURSDAY, DECEMBER 9, 2012
MERCURY 6.3 EAST OF VENUS
Mercury and Venus are both "inferior planets," meaning that they are closer to the Sun than Earth. As our home world occupies the third position, we have only two inferior planets (Mercury and Venus) and the remaining are superior worlds. See our two inferior planets in the eastern early morning sky. Distinguishing between them will not prove difficult as Venus is currently twenty-five times brighter than Mercury.
MONDAY, DECEMBER 10, 2012
MOON 4.0 DEGREES SSW OF SATURN
Saturn might be dimmer than Venus, but it's slightly higher in the sky. See the sixth planet and the waning crescent moon in the eastern pre-dawn sky. One aggravating note about Saturn: its most prominent and distinguishing feature, its rings, are not resolvable without a telescope. As it true with the other planets, the "naked-eye" Saturn resembles a star.
TUESDAY, DECEMBER 11, 2012
MOON 1.7 DEGREES SOUTH OF VENUS
It is convenient that one can see the Moon close to Saturn on Monday and then near Venus on Tuesday. By observing the eastern early morning sky on these successive dates, one can readily identify Saturn one day and Venus the next. Of course, distinguishing between these two planets is quite easy as Venus is considerably brighter.
THURSDAY, DECEMBER 13, 2012
GEMINID METEOR SHOWER
The only major meteor shower associated with an asteroid, one named 3200 Phaethon. (Granted, this body's composition remains largely unknown and therefore its asteroid designation is dubious.) Meteor showers occur when Earth moves through a particle stream a comet -or asteroid- releases as its travels close to the Sun. The body emitting this stream is the meteor shower's "parent." Phaethon is the parent of the Geminid meteor shower, so named as the meteors appear to emanate from a sky region around the Gemini constellation. As this shower peaks around the New Moon, we'll have an easier time observing the meteors. Provided observing conditions are favorable (you're in a dark region at least one light year from a city) perhaps as many as 20-30 meteors an hour will be observable.
THURSDAY, DECEMBER 13, 2012
Beginning of lunation 1113.
Just a quick reminder that the new moon is in the same part of the sky as the Sun and therefore not visible. Watch for the crescent moon in the western evening sky in a couple of nights.
SATURDAY, DECEMBER 15, 2012
MOON 5.5 DEGREES NNW OF MARS
Mars is low in the western evening sky (See "Planet Watch.") Tonight, see the ruddy red world close to the waxing crescent moon. Find both bodies just after sunset.
MONDAY, DECEMBER 17, 2012
SUN ENTERS SAGITTARIUS
The Sun appears to enter the region designated as "Sagittarius," a sky area around the constellation of the same name. The Sun seems to occupy Sagittarius on the first day of winter, when Sol is lowest in our sky. The Sun is not actually "moving" into Sagittarius. Instead, our planet is moving to the far side of the Sun relative to the stars comprising the Sagittarius pattern. Consequently, the Sun appears as though it is gradually inserting itself between us and Sagittarius.
THURSDAY, DECEMBER 20, 2012
FIRST QUARTER MOON
FRIDAY, DECEMBER 21, 2012
WINTER SOLSTICE (PICK EVENT!)
We realize the winter solstice happens every year, but we decided to designate winter's arrival as the month's pick event. After all, astronomically speaking, December is known as the time when winter begins. The Sun reaches its lowest altitude today and will gradually ascend until reaching the summer solstice on in June. Yet again, the Sun's apparent motion is illusory: its changing altitude results from our planet's tilt. This time of year, the North Pole is pointed away from the Sun, making the latter appear low in the sky. Six months from now, when our hemisphere is directed toward the Sun, it will occupy a higher position.
TUESDAY, DECEMBER 25, 2012
MOON 0.42 DEGREES OF JUPITER
We could have just as easily have selected this close Jupiter-moon gathering as the month's pick event. See the brilliant planet and gibbous moon together in the early evening eastern sky and then over in the late night western sky.
FRIDAY, DECEMBER 28, 2012
Let's talk about the Mid Winter Full Moon. The full moon that occurs around the winter solstice is the year's highest full moon. We remember that the Moon, like the planets, remains within a band around the ecliptic: the Sun's annual motion path through the sky. When the Moon is full, it is 180 degrees away from the Sun. The solstice points are also 180 degrees apart. The high summer solstice point is 180 degrees from the low winter solstice position. Since the winter solstice full moon is also 180 degrees from the Sun, the former will ride high along the ecliptic, just as the summer solstice full moon lurks low.
Find Mercury low in the eastern pre-dawn sky during the first half of December. The messenger planet vanishes into twilight later this month, but is at greatest elongation during the first week of December. VERDICT: If you truly want to see Mercury, venture out before the Sun during the first half of December.
Venus is Mercury's morning companion. It is brighter than Mercury, of course, and therefore easier to find. Venus remains visible all month. VERDICT: Though the second world grows gradually dimmer throughout December, it is an easy sight provided one is up and about before Sunrise.
Mars is technically visible all month, but it is not easy to find. Mars is the dimmest of the five naked eye planets* and quite low in the western evening sky. Having the Moon close to Mars on December 15th will help those who want to find the red world. VERDICT: Finding this faint world is not for the faint of heart. Look low in the west soon after dark. Mars' crimson tint makes it slightly easier to observe than it would be if it exhibited an indistinct white light.
JUPITER (PICK PLANET)
The King of the planets is our pick again this month. Though never as bright as Venus, Jupiter easily outshines all the other planets. It is also in the sky all night, as it reached opposition at month's beginning. (Venus is NEVER at opposition in our sky.) VERDICT: Jupiter is the pick for a reason. Bright, beautiful and easy to see! Find the fifth world tonight!
Though Jupiter is proudly perched on the sedan chair, Saturn is an ambitious aspirant and will find itself hoisted on the shoulders of the subjugated this spring. Saturn is rising higher and growing brighter in the eastern morning sky. You can use the Moon to find the Ring World on December 10th. VERDICT: Yes, it's the second dimmest planet, but don't let that discourage you. See Saturn a couple hours before sunrise. If such an early show time isn't to your liking, wait a few months for Saturn to appear in the evening.
*The present order of planets according to brightness:
Venus; Jupiter; Mercury, Saturn and Mars.