December 2011 Celestial Calendar & Observing notes c/o Dave Mitsky

[Big Dipper]

December 2011 Celestial Calendar & Observing Notes courtesy of Dave Mitsky (calendar data also reproduced in our forum calendar).

All times, unless otherwise noted, are UT.

12/1 Neptune is 6 degrees south of the Moon at 15:00

12/2 First Quarter Moon occurs at 9:52; the Lunar X (the Purbach or Werner Cross), an X-shaped illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to occur at 17:00

12/4 Uranus is 6 degrees south of the Moon at 8:00; Mercury is in inferior conjunction at 9:00

12/5 The earliest end of evening twilight at 40 degrees north latitude occurs today; Mercury is at perihelion today

12/6 The Moon is at apogee, subtending 29'52" from a distance of 405,414 kilometers (248,701 miles), at 1:00; Jupiter is 5 degrees south of the Moon at 20:00

12/8 The earliest sunset of the year at 40 degrees north latitude occurs today

12/10 A total lunar eclipse visible from western North America, Polynesia, Australia, and Asia occurs from 14:06 to 14:57; Full Moon (known as the Before Yule, Cold, Long Nights, and Oak Moon) occurs at 14:36; Uranus is stationary at 15:00

12/14 Mercury is stationary at 2:00; the peak of the Geminid meteor shower (100 to 120 per hour) occurs at 18:00

12/15 Mercury is at its greatest heliocentric latitude north today

12/17 Mars is 8 degrees north of the Moon at 13:00

12/18 Last Quarter Moon occurs at 0:48; the Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to occur at 20:06

12/20 Saturn is 7 degrees north of the Moon at 10:00

12/21 The shortest day (9 hours and 20 minutes) of the year at 40 degrees north latitude occurs today; Venus is at its greatest heliocentric latitude south today

12/22 The Moon is at perigee, subtending 32'16" from a distance of 364,800 kilometers (230,086 miles), at 3:00; the northern hemisphere winter solstice occurs at 5:30; Mercury is 7 degrees north of the first-magnitude star Antares (Alpha Scorpii) at 20:00

12/23 The peak of the Ursid meteor shower (10 per hour) occurs at 2:00; Mercury is at greatest western elongation (22 degrees) at 3:00; Mercury is 3 degrees north of the Moon at 4:00

12/24 New Moon (lunation 1101) occurs at 18:06

12/26 Jupiter is stationary at 11:00

12/27 Venus is 6 degrees south of the Moon at 11:00

12/28 A double Galilean satellite shadow transit (Europa’s shadow follows Ganymede’s) begins at 3:51 and ends at 3:55

12/29 Neptune is 6 degrees south of the Moon at 1:00; Pluto is in conjunction with the Sun at 8:00

12/31 Asteroid 1 Ceres is in conjunction with the Sun today; Uranus is 6 degrees south of the Moon at 16:00

Tycho Brahe, Johannes Kepler, Isaac Newton, and Arthur Eddington were born in December.

December 14’s Geminid meteor shower is compromised by a waning gibbous Moon. This shower, which is associated with the asteroid, or possible cometary nucleus, 3200 Phaethon, has become the most reliable one of the year. Geminids appear to originate from a radiant that’s a bit northwest of Castor (Alpha Geminorum). The Ursids, a normally minor meteor shower, peak on December 23. The radiant is located close to Kochab (Beta Ursa Minoris), some 15 degrees from the north celestial pole. For more on the Geminids, click on http://www.imo.net/calendar/2010#gem

The Moon is 6.0 days old and is located in Capricornus on December 1 at 0:00 UT. It attains its greatest northern declination (+22.5 degrees) for the month on December 10 and its greatest southern declination (-22.5 degrees) for the month on December 23. Longitudinal libration is at a maximum of +5.9 degrees on December 27 and a minimum of -5.7 degrees on December 14. Latitudinal libration is at a maximum of +6.8 degrees on December 17 and a minimum of -6.9 degrees on December 2 and -6.8 on December 30. A 51-minute-long total lunar eclipse that’s visible in its entirety from Polynesia, Australia, and Asia takes place on December 10. In western North America, the eclipse is ongoing as the Moon sets. Partial eclipse begins at 7:45 a.m. EST and ends at 11:18 a.m. EST. Total eclipse begins at 9:06 a.m. EST and ends at 9:57 a.m. EST. Greatest eclipse occurs at 9:32 a.m. EST, at which time the Moon is at the zenith as seen from the Pacific Ocean in the vicinity of the island of Guam. The Moon will be located in Taurus at the time. There’s additional information on the eclipse posted at http://eclipse.gsfc.nasa.gov/OH/OH2011.html#LE2011Dec10T and in an article on pages 58 and 59 of the December 2011 issue of Sky & Telescope. Visit http://www.astronomyblogs.com/member/saberscorpx/?xjMsgID=50821 for tips on spotting extreme crescent Moons. Browse http://www.lunar-occultations.com/iota/ for information on upcoming lunar occultations. 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. Winter solstice for the northern hemisphere occurs when the Sun is farthest south for the year on December 22.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on December 1: Mercury (magnitude 3.3, 9.7", 5% illuminated, 0.69 a.u., Ophiuchus), Venus (magnitude -3.9, 11.5", 89% illuminated, 1.45 a.u., Sagittarius), Mars (magnitude 0.8, 7.1", 90% illuminated, 1.32 a.u., Leo), Jupiter (magnitude -2.8, 47.6", 100% illuminated, 4.14 a.u., Aries), Saturn (magnitude 0.8, 16.0", 100% illuminated, 10.38 a.u., Virgo), Uranus (magnitude 5.8, 3.5", 100% illuminated, 19.68 a.u., Pisces), Neptune (magnitude 7.9, 2.2", 100% illuminated, 30.16 a.u., Aquarius), and Pluto (magnitude 14.1, 0.1", 100% illuminated, 33.00 a.u., Sagittarius).

During the evening, Venus can be found in the southwest, Jupiter in the southeast, and Uranus and Neptune in the south. Mars is in the east and Jupiter and Uranus are in the west, at midnight. In the morning, Mercury and Saturn are located in the southeast and Mars is in the south.

At mid-month, Venus sets at 7:00 p.m. local time, Mars rises at 11:00 p.m. local time and transits at 6:00 a.m. local time, Jupiter transits at 8:00 p.m. local time and sets at 3:00 a.m. local time, and Saturn rises at 3:00 a.m. local time for observers at latitude 40 degrees north.

Mercury is visible in morning twilight during the second half of the month. It is in inferior conjunction with the Sun on December 4 and at perihelion the following day. Mercury reaches greatest western elongation on December 23. On December 23, the speediest of planets is three degrees north of the Moon. Mercury increases in illumination from 5 to 79% and shrinks in apparent size from 9.7 to 5.8 arc seconds.

During the course of the month, Venus increases in illuminated extent from 24 to 45%, while its apparent size decreases from 42 to 27 arc minutes. However, its brightness remains constant at magnitude -3.9. At mid-month, the brightest planet is 30 degrees in altitude when the Sun rises. The Moon is six degrees north of Venus on December 27.

Mars increases in apparent size from 7.1 to 8.9 arc minutes and in brightness from magnitude 0.8 to -0.2 this month. The northern hemisphere of Mars is facing the Earth so its north polar cap should be visible with a telescope of moderate aperture. During the last two weeks of December, the dark surface feature known as Syrtis Major will be well-placed for observers in North America after 1:00 a.m. local time.

Jupiter culminates in the south near the Aries-Pisces border at approximately 8:00 p.m. EST. The King of the Planets is five degrees south of the Moon on December 6. Jupiter resumes direct or prograde (eastern) motion on December 26. Browse http://skyandtelescope.com/observing/objects/planets/article_107_1.asp in order to determine transit times of Jupiter’s central meridian by the Great Red Spot. Data on the Galilean satellites is available at http://skytonight.com/observing/objects/javascript/3307071.html#

The Ringed Planet is well-placed in the dawn sky some five degrees southwest of the first-magnitude star Spica. In late December, Saturn’s rings are inclined by 15 degrees, the maximum tilt for 2011, making the Cassini Division an easy telescopic target. The Moon is seven degrees south of Saturn on the night of December 20. Giovanni Cassini discovered the Saturnian satellite Rhea on December 23, 1672. For information on the five brightest satellites of Saturn, browse http://skytonight.com/observing/objects/javascript/3308506.html

Uranus is approximately seven degrees south of the fourth-magnitude star Omega Piscium. On December 10, Uranus resumes prograde motion. Uranus is positioned six degrees south of the Moon on December 31.

Neptune can be found near the border of Aquarius and Capricornus, about 1.5 degrees northwest of the fourth-magnitude star Iota Aquarii. The eighth planet lies six degrees south of the Moon on December 29.

Finder charts for Uranus and Neptune appear on page 53 of the September 2011 issue of Sky & Telescope and are posted online at http://media.skyandtelescope.com/documents/Uranus-Neptune-2011.pdf

The dwarf planet Pluto is in conjunction with the Sun on December 29 and is not visible this month.

Comet C/2009 P1 (Garradd) shines at approximately sixth magnitude as it glides northward through Hercules. The comet is actually better placed in the morning sky during the final ten days of December. A finder chart can be found on page 56 of the November 2011 issue of Sky & Telescope. Visit http://cometchasing.skyhound.com/ for additional information on comets that are visible this month.

During December, asteroid 15 Eunomia shines at eighth-magnitude as it heads southwestward through Perseus. It’s positioned less than a degree to the northwest of the fourth-magnitude star Xi Persei and is even closer to NGC 1499 (the California Nebula) on December 1.

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

The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in magnitude from 2.1 to 3.4, on December 2, 5, 8, 11, 13, 16, 19, 22, 25, 28, and 31. Consult http://www.skyandtelescope.com/observing/objects/variablestars/Minima_of_Algol.html for the times of the eclipses. For more on Algol, see http://stars.astro.illinois.edu/sow/Algol.html and http://www.solstation.com/stars2/algol3.htm

The famous pulsating variable star Mira (Omicron Ceti), the Wonderful, should still be visible without optical aid this month. Click on http://spider.seds.org/spider/Vars/mira.html for further information on Mira.

One hundred and five 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)

One hundred deep-sky objects for December: NGC 891 (Andromeda); IC 342, K6, St23, Tom 5 (Camelopardalis); Be65, IC 1848, K4, Mel15, NGC 896, NGC 1027, St2, Tr3 (Cassiopeia); M77, NGC 788, NGC 835, NGC 864, NGC 908, NGC 936, NGC 955, NGC 958, NGC 1015, NGC 1016, NGC 1022, NGC 1042, NGC 1052, NGC 1055, NGC 1087, NGC 1094 (Cetus); IC 2006, NGC 1084, NGC 1140, NGC 1187, NGC 1199, NGC 1209, NGC 1232, NGC 1291, NGC 1300, NGC 1309, NGC 1332, NGC 1337, NGC 1353, NGC 1357, NGC 1395, NGC 1400, NGC 1407, NGC 1421, NGC 1426, NGC 1440, NGC 1452, NGC 1453, NGC 1461 (Eridanus); NGC 1079, NGC 1097, NGC 1201, NGC 1292, NGC 1316 (Fornax I Galaxy Cluster), NGC 1317, NGC 1326, NGC 1344, NGC 1350, NGC 1360, NGC 1365, NGC 1371, NGC 1374, NGC 1379, NGC 1380, NGC 1381, NGC 1387, NGC 1398, NGC 1404, NGC 1406, NGC 1425 (Fornax); Bas10, Cz8, IC 351, IC 2003, K5, Mel 20, M34, NGC 869, NGC 884, NGC 957, NGC 1023, NGC 1058, NGC 1161, NGC 1245, NGC 1275 (Perseus I Galaxy Cluster), NGC 1333, NGC 1342, NGC 1444, Tr2 (Perseus); M45 (Taurus); NGC 777, NGC 784, NGC 890, NGC 925, NGC 949, NGC 959, NGC 978A/B (Triangulum)

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)

The objects listed above are located between 2:00 and 4:00 hours of right ascension.