What's Up in the Night Sky

December 2024 - Vol. 28, No. 12

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

Some believe the winter night sky is the most beautiful of the year! By mid-month, misty Pleiades, the famous open star cluster of the constellation Taurus, is visible due S. at 10 pm. Although part of the constellation Taurus, it lies above its "lazy V" asterism whose brightest star, orange-tinted Aldebaran, glows near the point of the lower branch of the "V". Above are the constellations Perseus, Cassiopeia (whose "W" shaped asterism is unmistakable) and Auriga. Lovely Orion, whose asterism reminds me of a slightly lopsided hour glass, moves upwards from the SE. Note its three "belt" stars located at the "pinch" of the hour glass. The hazy object below the middle belt star is M42, the Great Orion Nebula, a region of space where stars are being born. Orion is followed by the bright stars Procyon (Canis Minor) and Sirius (Canis Major). Along with the bright star Betelgeuse (Orion), these three stars form the famous "Winter Triangle". To the E shine the Gemini twins, Castor and Pollux. In the SW, the diamond-shaped "Great Square of Pegasus" stands on one corner while high in the N, Ursa Major's asterism, the Big Dipper, stands on its "bowl".

MERCURY too close to the Sun to be seen in the first half of the month, emerges in the evening sky will be seen best around December 25. VENUS in the evening sky, begins to appear higher for the northern observers. MARS in the constellation Cancer begins retrograde motion on December 7, shining at -1.0 by month's end. JUPITER reaches opposition on December 7, shining at -2.8 mag. SATURN in the evening sky, sets before midnight most of the month. URANUS, moves in Aries, still in retrograde motion after last month's opposition. NEPTUNE is in the constellation Pisces, set before midnight.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times or check with the U.S. Naval observatory. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
04	Venus 2 deg. N. of Moon.
06	Mercury at perihelion. Mercury at inferior conjunction.
07	Jupiter at opposition. Mars stationary.
08	Saturn 0.3 deg. S. of the Moon, occultation from Indonesia, Philippines, NW edge of Australia, NW Micronesia, most of Japan, and Aleutian islands. Neptune stationary.
09	Neptune 0.8 deg. S. of Moon, occultation from most of Asia, Philippines, and Alaska.
12	Moon at perigee.
13	Uranus 4 deg. S. of the Moon. Moon in the Pleiades star cluster (M-45).
14	Geminid meteor peak. This meteor shower is unusual in that it is associated with the 3200 Phaethonan asteroid that orbits the Sun every 1.4 years. This year the full Moon will wash out the sky. Jupiter 5 deg. S. of Moon.
15	December's full moon is often called the "Cold" Moon as it was named by the native Americans Mohawk tribe due to the obvious cold of Winter in North America. Mercury stationary.
16	Mercury at greatest heliocentric latitude N.
18	Mars 0.9 deg. S. of Moon, occultation from northern Russia, N. Alaska, N. Canada, Greenland, NW half of Europe, NW tip of Africa.
21	Solstice, Winter begins in the northern hemisphere, Summer in the south.
22	The Ursid meteor shower produces 10 meteors at its peak.
24	Moon at apogee. Alpha Virginis, Spica, 0.2 deg. S. of Moon, occultation from E. China, most of Japan, Micronesia, most of Melanesia, and parts of Polynesia.
28	Alpha Scorpii, Antares, 0.09 deg. S. of Moon, occultation from E. Polynesia, and southern South America.

Lunar Almanac for December 2024

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 01, 30	Deep Space Objects
	1st. Qtr 08	Planets & Moon
	Full 15	Moon
	Last Qtr 22	Deep Space & Planets

Topic of the month: Celestial Twins

The evening sky welcomes the northern hemisphere to longer nights and views of the celestial vault; while in the south, night is shrinking and Summer has arrived. The constellation of Gemini should be visible from a modest site by 10 pm for citizens of Earth in the northern hemisphere. For many human civilizations, the constellation was associated with twins.

Two of the constellations bright stars, Castor and Pollux, are less than 5 degrees apart in the night sky from Earth. Pollux, the brightest star in the constellation, shines at 1.14 mag. Despite its brightness, it has been designated as Beta Geminorum (Beta Gem). Castor is designated as the Alpha star of Gemini. It is a mere 52 light years away from Earth. Castor has a visual magnitude of 1.93. It was discovered to be a double star in 1678, although as observational methods improved, it was found to have six separate components.

Amateur astronomers will want to look for an object in the constellation of Gemini known as NGC 2392 or the Eskimo Nebula. This object is an excellent planetary nebula. Although it is not quite as large as the more popular "Ring Nebula", M57 in Lyra, NGC 2392 is brighter at 8th magnitude. The central star of this planetary is also much brighter. At 8th magnitude it is easily seen in amateur telescopes, whereas the central star of the Ring is too faint for the small telescope. Don't look at CCD images and expect your view to approach the color and detail of those. The visual observation has its own charm and wonder. On a good night the edges of the Eskimo's parka will thrill the eye.

No discussion of Gemini is complete without mention of the huge star cluster known as M35. This cluster spans an area greater than the full moon and is visible at dark sites with the naked eye. The cluster was known before the time of Messier, but was found in his catalog and so the M designation has remained. The cluster contains at least 120 stars covering an area of 30 light years. Viewing this object with an amateur instrument gives one the impression of many double stars. Also visible as a fuzzy patch of light in the same field of M35, is the rich cluster NGC 2158. This cluster is more distant than M35 and would take a large amateur instrument at high power to resolve into stars.

--See You Under the Stars!
Astra for Astra's Almanac

The star chart above was generated by Stellarium, a free open source planetarium program. The above image was created by Dawn Jenkins, using Stellarium and a graphic editing program to format the image for this web page. Editing was done for educational purposes only. Stellarium offers much more to amateur astronomers and is being used in planetariums and to guide telescopes in the field. Simple charts like the one above can be used on the internet for non-profit, illustration purposes. Proper credit is due of course! Thank you to the makers of this fine program from Astra's Star Gate.

--See You Under the Stars!
Astra for Astra's Almanac