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December 2009 Celestial Calendar

Dave Mitsky

Note: All times in UTC (EST + 5)

The famous astronomers Tycho Brahe, Johannes Kepler, Isaac Newton, and Arthur Eddington were all born in December.

The peak of the Geminid meteor shower, which is associated with the asteroid (or possible cometary nucleus) 3200 Phaethon, takes place after midnight on the morning of December 14. Geminids appear to originate from a radiant that is a bit northwest of Alpha Geminorum (Castor). The Ursids, a normally minor meteor shower, peak late in the morning of December 22. The radiant is located close to Beta Ursa Minoris (Kochab), some 15 degrees from the north celestial pole. For more on these meteor showers, click on http://www.imo.net/calendar/2009#gem

The Moon occults M45 (the Pleiades) on December 1 and December 29. See http://www.lunar-occultations.com/iota/pleiades/pleiades.htm for further information on these events. The first-magnitude star Spica is less than five degrees southeast of the Moon on the morning of December 11. A partial lunar eclipse that is best seen from Australia, Asia, Africa, and Europe takes place from on December 31. Observers in the far northwest portion of North America can see the start of the eclipse. The end of the eclipse is visible from far northeastern North America. There's additional information on this minor lunar eclipse at http://eclipse.gsfc.nasa.gov/OH/OH2009.html#LE2009Dec31P

The Moon is 14.2 days old and is located in Aries on December 1 at 0:00 UT. It attains its greatest northern declination (+25.8 degrees) for the month on December 2 and December 30 and its greatest southern declination (-25.8 degrees) for the month on December 16. Latitudinal libration is at a maximum of +6.8 degrees on December 11 and a minimum of -6.8 degrees on December 26. Longitudinal libration is at a maximum of +6.0 degrees on December 12 and a minimum of -7.3 degrees on December 26. Visit http://www.astronomyblogs.com/member/saberscorpx/?xjMsgID=50821 for tips on spotting extreme crescent Moons. Times and dates for the lunar light rays predicted to occur this month are available at http://www.lunar-occultations.com/rlo/rays/rays.htm

The Sun is located in Ophiuchus on December 1. When the winter solstice for the northern hemisphere occurs on December 21, there will be 9 hours and 20 minutes of daylight at latitude 40 degrees north.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on December 1: Mercury (-0.5 magnitude, 5.1", 92% illuminated, 1.33 a.u., Ophiuchus), Venus (-3.9 magnitude, 10.0", 99% illuminated, 1.67 a.u., Libra), Mars (-0.1 magnitude, 9.9", 91% illuminated, 0.95 a.u., Leo), Jupiter (-2.3 magnitude, 37.7", 99% illuminated, 5.23 a.u., Capricornus), Saturn (1.0 magnitude, 16.9", 100% illuminated, 9.83 a.u., Virgo), Uranus (5.8 magnitude, 3.5", 100% illuminated, 20.10 a.u., Aquarius), Neptune (7.9 magnitude, 2.2", 100% illuminated, 30.51 a.u., Capricornus), and Pluto (14.1 magnitude, 0.1", 100% illuminated, 32.72 a.u., Sagittarius).

Mercury and Jupiter lie in the southwest and Uranus in the south in the evening sky. At midnight, Mars can be found in the east. In the morning, Mars is in the southwest and Saturn is in the south. At midmonth from 40 degrees north latitude, Mars rises at approximately 9:00 p.m. EST and transits the meridian at 4:00 a.m. EST, Jupiter sets at 9:00 p.m. EST, Saturn rises at 1:00 a.m. EST and transits at 7:00 a.m. EST.

Mercury shines at magnitude -0.5 for the first three weeks of the month. It's positioned five degrees above the horizon thirty minutes after the Sun sets on December 9. When it reaches greatest eastern elongation on December 18, the speediest of planets spans 6.7 arc seconds and is 61% illuminated. Mercury reaches an altitude of eight degrees a half hour after sunset that evening and is accompanied by a thin crescent Moon located six degrees to its upper left. Mercury becomes a thin crescent, illuminated just 10% and subtending 9.4 arc seconds, and fades from sight by the end of 2009.

As it heads for superior conjunction in January, Venus is lost in the glare of the Sun and is not visible this month.

Mars rises five hours after sunset in early December. By the end of the month, it rises three hours after the Sun sets. As the Earth catches up to Mars during December, the Red Planet doubles in brightness. Mars approaches to within eleven degrees of Regulus before beginning its retrograde loop back towards Cancer on December 21. Mars subtends 12.7 arc seconds in apparent size and shines at -0.7 magnitude on December 31. Since the northern hemisphere of Mars is inclined towards the Earth, the north polar cap is readily visible. Syrtis Major, a triangular surface feature, is well-placed at midnight during the first week of the month; the Amazonis Basin and the Tharsis Ridge during the second; and Solis Lacus, also known as the Eye of Mars, during the third. An article on observing Mars during the current apparition appears on pages 57 to 61 of the December issue of Sky & Telescope.

Jupiter's 2009 apparition is nearing an end. At the end of December, the giant planet sets before the end of twilight. Jupiter is just 34 arc seconds due south of Neptune on December 19 and is less than 0.6 degrees away from Neptune through December 22. This will be the last conjunction of Jupiter and Neptune to take place for some 13 years. Jupiter is less than two degrees due north of the third-magnitude star Delta Capricorni (Deneb Algedi) on the evening of December 20. Mutual events involving the Galilean satellites take place on December 2 at 9:08 p.m. EST when Io occults Europa and December 14 at 7:26 p.m. EST when Europa occults Io. A double Galilean satellite shadow transit begins at 8:34 p.m. EST on the evening of December 20. Browse http://skyandtelescope.com/observing/objects/planets/article_107_1.asp to determine transits of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at http://skytonight.com/observing/objects/javascript/3307071.html#

Saturn is near the celestial equator this month. As December begins, Saturn rises at approximately 1:30 a.m. EST. By mid-December, the Ringed Planet rises about 40 minutes after midnight and transits the meridian six hours later. On December 31, it clears the horizon around 1:30 a.m. EST. Saturn reaches western quadrature on December 25. Its rings are inclined by 4.3 degrees on December 1 and reach a maximum inclination of 4.9 degrees by the end of the year. The Moon is 8 degrees from Saturn on December 10. Eighth-magnitude Titan, Saturn's largest and brightest satellite, is close to the planet on December 1, 9, 17, and 25. Iapetus is due north of Saturn on December 21. For further information on the five brightest satellites of Saturn, browse http://skytonight.com/observing/objects/javascript/3308506.html

This month Uranus lies six degrees due west of the fifth-magnitude star 27 Piscium. It sets shortly before midnight.

For the first three weeks of the month, Neptune can be found north of the third-magnitude star Delta Capricorni (Deneb Algedi) and the fourth-magnitude star Gamma Capricorni. From December 15 to December 25, Neptune, which is tiny at 2.2 arc seconds in apparent size, is located within one degree of Jupiter, which decreases in apparent size from 36.3 to 35.4 arc seconds during that period.

The dwarf planet Pluto is in conjunction with the Sun on December 24 and is not visible this month.

The tenth-magnitude comet C/2007 Q3 (Siding Spring) travels northeastward through Coma Berenices during December. It passes north of the globular clusters M53 and NGC 5053 on the mornings of December 12 and December 13. Some other comets to look for this month include the periodic comets 217P/LINEAR, 211P/Hill, and 81P/Wild. Visit http://cometchasing.skyhound.com/ for additional information on comets that are visible this month.

The ninth-magnitude asteroid 18 Melpomene heads northeastward through Cetus this month, passing within one degree of the stars Theta Ceti (magnitude 4.0) and 44 Ceti (magnitude 6.2) from December 6 to December 13. On December 9, asteroid 2309 Mr. Spock makes its closest approach to the Earth (1.80 a.u.). Asteroid 19 Fortuna (magnitude 9.3) is at opposition on December 9. Other asteroids reaching opposition this month include 11 Parthenope (magnitude 9.9), 52 Europa (magnitude 10.1), 111 Ate (magnitude 10.8), 128 Nemesis (magnitude 10.7), and 324 Bamberga (magnitude 9.8).

A free star map for December can be downloaded at http://www.skymaps.com/downloads.html

Binary and Multiple Stars for December

Gamma Andromedae, 59 Andromedae, Struve 245 (Andromeda); Struve 362, Struve 374, Struve 384, Struve 390, Struve 396, Struve 400, Struve 419, Otto Struve 67 (Camelopardalis); Struve 191, Struve Iota Cassiopeiae, Struve 263, Otto Struve 50, Struve 283, Struve 284 (Cassiopeia); 61 Ceti, Struve 218, Omicron Ceti, Struve 274, Nu Ceti, h3511, 84 Ceti, h3524, Lambda Ceti, Struve 330 (Cetus); h3527, h3533, Theta Eridani, Rho Eridani, Struve 341, h3548, h3565, Tau-4 Eridani, Struve 408, Struve 411, h3589, h3601, 30 Eridani, 32 Eridani (Eridanus); h3478, h3504, Omega Fornacis, Eta-2 Fornacis, Alpha Fornacis, See 25, Xi-3 Fornacis, h3596 (Fornax); Struve 268, Struve 270, h1123, Otto Struve 44, h2155, Nu Persei, Struve 297, Struve 301, Struve 304, Eta Persei, Struve 314, Otto Struve 48, Tau Persei, Struve 331, Struve 336, Es588, Struve 352, Struve 360, Struve 369, Struve 382, Struve 388, Struve 392, Struve 410, Struve 413, Struve 425, Otto Struve 59, Struve 426, 40 Persei, Struve 434, Struve 448, Es277, Zeta Persei, Struve 469, Epsilon Persei, Es878 (Perseus); Struve 399, Struve 406, Struve 401, Struve 422, Struve 430, Struve 427, Struve 435, 30 Tauri (Taurus); Epsilon Trianguli, Struve 219, Iota Trianguli, Struve 232, Struve 239, Struve 246, 10 Trianguli, Struve 269, h653, 15 Trianguli, Struve 285, Struve 286, Struve 310 (Triangulum)

Challenge binary star for December: 48 Cassiopeiae (Cassiopeia)
Notable carbon star for December: U Camelopardalis
Notable variable star for December: Omicron Ceti (Mira)

Top ten binocular deep-sky objects for December:
M34, M45, Mel15, Mel20, NGC 869, NGC 884, NGC 1027, NGC 1232, St2, St23
Top ten deep-sky objects for December:
M34, M45, M77, NGC 869, NGC 884, NGC 891, NGC 1023, NGC 1232, NGC 1332, NGC 1360
Challenge deep-sky object for December: vdB14 (Camelopardalis)