December Celestial Calendar by Dave Mitsky
All times, unless otherwise noted, are UT (subtract five hours and, when appropriate, one calendar day for EST)
12/1 Neptune is at eastern quadrature at 1:00; Mercury is 7.1 degrees south of the Moon at 5:00; Mercury is at its greatest heliocentric latitude south (-7.0 degrees) at 21:00
12/2 Mercury is at its greatest declination south (-25.8 degrees) for the year at 17:00
12/3 Asteroid 4 Vesta is stationary at 4:00; Venus is 5.8 degrees south of the Moon at 11:00
12/4 The earliest end of evening twilight at 40 degrees north takes place today
12/5 Mars is 2.9 degrees south-southeast of the Moon at 9:00
12/6 The Lunar X (the Purbach or Werner Cross), an X-shaped clair-obscure illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to occur at 16:36; the Moon is at the descending node at 17:37; Neptune is 0.67 degree south-southeast of the Moon, with an occultation taking place in western Europe, Iceland, Greenland, southern and eastern Canada, the United States, and Central America, at 22:00
12/7 First Quarter Moon occurs at 9:03; the earliest sunset of the year at 40 degrees north latitude occurs at 16:35
12/9 Uranus is 2.9 degrees north-northwest of the Moon at 21:00
12/10 Saturn is in conjunction with the Sun at 12:00
12/11 Mercury is at greatest eastern elongation (20.8 degrees) at 4:00
12/12 The Moon is 9.0 degrees south-southeast of the bright open cluster M45 in Taurus at 13:00; the moon is at perigee, subtending 33'20" from a distance of 358,461 kilometers (222,737 miles), at 23:29
12/13 The Moon is 0.47 degree north-northwest of the first-magnitude star Aldebaran (Alpha Tauri), with an occultation taking place in northwest Africa, far western Europe, far southern Greenland, southern and eastern Canada, the United States, and northern Mexico, at 4:00
12/14 The peak of the Geminid meteor shower (100 to 120 per hour) occurs at 0:00; Full Moon (known as the Before Yule, Cold, Long Nights, and Oak Moon) occurs at 0:05; the Moon is 5.4 degrees south of the bright open cluster M35 in Gemini at 16:00
12/15 Asteroid 1 Ceres is stationary in right ascension at 7:00
12/17 The Moon is 3.7 degrees south of the bright open cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 3:00
12/18 The Sun enters Sagittarius at 2:00; the Moon is 0.98 degree south-southwest of the first-magnitude star Regulus (Alpha Leonis), with an occultation taking place in far southern Australia and portions of Antarctica, at 18:00
12/19 The Moon is at the ascending node at 4:47; Mercury is stationary in right ascension at 7:00
12/20 Mercury is 1.9 degrees southwest of Pluto at 12:00; Mercury is at the ascending node at 23:00
12/21 Last Quarter Moon occurs at 1:56; winter solstice in the northern hemisphere occurs at 10:44
12/22 Mars (10.2 degrees heliocentric longitude) and Jupiter (190.2 degrees heliocentric longitude) are at heliocentric opposition at 6:00; the peak of the Ursid meteor shower (10 per hour) occurs at 9:00; Jupiter is 2.3 degrees south-southwest of the Moon at 18:00; the Curtiss Cross, an X-shaped clair-obscure illumination effect located between the craters Parry and Gambart, is predicted to occur at 18:27
12/24 The equation of time equals zero at 22:00
12/25 The Moon is at apogee, subtending 29'26" from a distance of 405,870 kilometers (252,196 miles), at 5:55; Mercury is at perihelion (0.31 a.u. from the Sun) at 15:00
12/27 The Moon is 3.6 degrees north of Saturn at 21:00
12/28 Jupiter is at its greatest heliocentric latitude north (1.3 degrees) at 5:00; Mercury is in inferior conjunction at 19:00
12/29 The Moon is at its southernmost declination (-18.96 degrees) of the year at 2:00; Mercury is 1.8 degrees south of the Moon at 5:00; New Moon (lunation 1163) occurs at 6:53; Uranus is stationary in right ascension at 16:00
12/31 Comet 45P/Honda–Mrkos–Pajdušáková is at perihelion (0.53 a.u. from the Sun) at 4:00
Tycho Brahe, Johannes Kepler, Isaac Newton, and Arthur Eddington were born in December.
Giovanni Cassini discovered the Saturnian satellite Rhea on December 23, 1672.
Unfortunately, the peak of December 14th’s Geminid meteor shower coincides with Full Moon this year. The Geminids, which are associated with the Palladian asteroid, or possible cometary nucleus, 3200 Phaethon, have become the most reliable meteor shower of the year. Geminid meteors appear to originate from a radiant that’s just northwest of Castor (Alpha Geminorum). That radiant lies almost at the zenith at 2:00 a.m. local time. The Ursids, a normally minor meteor shower, peak on the morning of December 22nd. Moonlight will interfere with observing the shower. The radiant is located close to Kochab (Beta Ursa Minoris), some 15 degrees from the north celestial pole. An article on the 2016 Geminids and 2016 Ursids appears on page 48 of the December issue of Sky & Telescope. See https://in-the-sky.o...20161214_11_100 and http://www.imo.net/calendar/2016#gem for additional information on the Geminids and https://in-the-sky.o...20161222_11_100 and http://www.imo.net/r...endar/2016/#urs for more on the Ursids.
Information on Iridium satellite flares and passes of the ISS, the Tiangong-1, the X-37B, the HST, and other satellites can be found at http://www.heavens-above.com/
The Moon is 1.5 days old, is illuminated 2.1%, subtends 29.52 arc minutes, and is located in Ophiuchus on December 1st at 0:00 UT. Large tides will take place on December 13th through December 16th. Full Moon occurs on December 14th. Due to the position of the ecliptic, the Moon reaches its highest point in the sky for the year in December. It attains its greatest northern declination (+18.9 degrees) for the month on December 15th and its greatest southern declinations (-18.9 degrees) on December 2nd and (-18.9 degrees) on December 29th. Longitudinal libration is at a maximum of +7.5 degrees on December 19th and a minimum of -7.1 degrees on December 7th. Latitudinal libration is at a maximum of +6.5 degrees on December 13th and a minimum of -6.6 degrees on December 27th. The Moon occults Neptune on December 6th, the first-magnitude star Aldebaran on December 13th, and the first-magnitude star Regulus on December 18th from certain parts of the world. New Moon occurs on December 29th. Consult http://www.lunar-occ...ota/iotandx.htm for more on these events. Visit http://saberdoesthes...does-the-stars/ for tips on spotting extreme crescent Moons and http://www.curtrenz.com/moon.html for Full Moon data. Times and dates for the lunar crater light rays predicted to occur this month are available at http://www.lunar-occ...o/rays/rays.htm
The Sun is located in Ophiuchus, a non-traditional constellation of the zodiac, on December 1st. Sol enters Sagittarius on December 18th. Winter solstice for the northern hemisphere occurs when the Sun is farthest south for the year on December 21st. It is the shortest "day" of the year (9 hours and 20 minutes at latitude 40 degrees north).
Brightness, apparent size, illumination, distance from the Earth in astronomical units (a.u.), and location data for the planets and Pluto on December 1st: Mercury (magnitude -0.5, 5.5", 83% illuminated, 1.22 a.u., Sagittarius), Venus (magnitude -4.2, 16.8", 69% illuminated, 0.99 a.u., Sagittarius), Mars (magnitude +0.6, 6.5", 88% illuminated, 1.44 a.u., Capricornus), Jupiter (magnitude -1.8, 32.9", 99% illuminated, 6.00 a.u., Virgo), Saturn (magnitude +0.5, 15.1", 100% illuminated, 11.02 a.u., Ophiuchus), Uranus (magnitude +5.8, 3.6", 100% illuminated, 19.49 a.u. on December 16th, Pisces), Neptune (magnitude +7.9, 2.3", 100% illuminated, 30.19 a.u. on December 16th, Aquarius), and Pluto (magnitude +14.3, 0.1", 100% illuminated, 34.14 a.u. on December 16th, Sagittarius).
During the evening, Mercury and Venus can be found in the southwest, Mars and Neptune in the south, and Uranus in the southeast. Uranus is in the west at midnight. In the morning, Jupiter and Saturn are located in the southeast.
At midmonth, Mercury is visible during evening twilight, Venus sets at 8:00 p.m. local time, Mars sets at 10:00 p.m. local time, and Jupiter rises at 2:00 a.m. local time for observers at latitude 40 degrees north.
Mercury is well placed in the early evening sky from December 1st through December 19th. The speediest planet is at its greatest heliocentric latitude south on December 1st, reaches greatest eastern elongation on December 11th, and is stationary in right ascension on December 19th. Mercury is at the ascending node on December 20th and is in inferior conjunction with the Sun on December 28th.
As the distance between Venus and the Earth decreases, Venus continues to brighten and grow in apparent size, while decreasing in the degree to which it is illuminated. The brightest planet lies 5.8 degrees south of the Moon on December 3rd. Venus leaves Sagittarius and enters Capricornus on December 12th.
Mars departs Capricornus and enters Aquarius on December 15th. The Red Planet drops below six arc seconds in apparent diameter by month’s end.
Jupiter rises at approximately 2:30 a.m. local time early in the month and at 1:00 a.m. local time at the end of December. It increases in apparent size from 32.9 arc seconds to 35.4 arc seconds this month. The gas giant lies 2.0 degrees south of the twenty-three-day-old Moon on December 22nd. Jupiter is at its greatest heliocentric latitude north on December 28th. Ganymede emerges from Jupiter’s shadow for observers in western North America at 12:02 UT (4:02 a.m. PST) and is occulted by the planet at 13:24 UT (5:24 a.m. PST) on December 3rd. Callisto passes due north of Jupiter’s disk on the morning of December 11th. Galilean satellite transits take place on the mornings of December 14th (Ganymede followed later by Io) and December 17th (Europa). Click on
http://www.skyandtel...watching-tools/ or consult page 50 of the December issue of Sky & Telescope to determine transit times of the central meridian by the Great Red Spot. Data on Galilean satellite positions and events is available online at http://www.skyandtel...watching-tools/ and http://www.nakedeyep...er.htm#jupmoons and on page 51 of the December issue of Sky & Telescope.
Saturn is in conjunction with the Sun on December 10th and consequently is not visible until the very end of the month. It rises almost 90 minutes before sunrise on December 31st.
Uranus (magnitude +5.8) is located less than one degree east of the fifth-magnitude star Zeta Piscium for the entire month. It sets after midnight. The planet is positioned 52 arc minutes from the star on December 1st and just 35 arc minutes from it by the end of the month. It lies 2.9 degrees north-northwest of the Moon on December 9th. Uranus is stationary on December 29th and resumes direct or prograde (eastern) motion on the same day.
Neptune sets in the late evening. The ice giant is at eastern quadrature on December 1st and is occulted by the Moon on December 6th. Neptune (magnitude +7.9, 2.2 arc seconds in apparent diameter) and Mars (magnitude +0.9, 5.7 arc seconds in apparent diameter) undergo a historically close conjunction in Aquarius on December 31st. The two planets will be 9.8 arc minutes apart for observers on the East Coast and just 1.3 arc minutes for observers in Hawaii one hour prior to the time that they set. It will be the closest the two planets have been in more than 700 years.
See http://www.curtrenz.com/uranep.html for additional information on Uranus and Neptune.
Finder charts for Uranus and Neptune appear on page 50 of the October issue of Sky & Telescope. A finder chart for Uranus also appears on page 49 of the December issue of Sky & Telescope. Online finder charts for the two planets can be found at http://www.nakedeyep....com/uranus.htm and http://www.nakedeyep...com/neptune.htm and also at http://www.skyandtel...6_Finders.pdf
The dwarf planet Pluto will not be visible again until next year.
For more on the planets and how to locate them, see http://www.nakedeyeplanets.com/
Comet 45/P Honda-Mkros- Pajdušáková heads northeastward through Capricornus during the second half of the month. On December 15th, this periodic comet, which passes into the inner solar system every 5.25 years, is about 15 degrees above the horizon one hour after sunset. The ninth-magnitude globular cluster M75 in Sagittarius lies 1.5 degrees north-northwest of the comet on that date. Comet 45/P Honda-Mkros-Pajdusakova may brighten to eighth magnitude as December winds down. Visit http://cometchasing.skyhound.com/ and http://www.aerith.ne...t/future-n.html for additional information on comets that are visible this month.
The dwarf planet/asteroid 1 Ceres glides northeastward through Cetus during December. It decreases in brightness from magnitude +8.1 to magnitude +8.6 as the month progresses. Ceres lies about three degrees to the east of 42 Ceti (magnitude +5.6) during the first half of the month. Asteroid 68 Leto (magnitude +10.6) is at opposition on December 20th and 22 Kalliope (magnitude +10.0) on December 26th. Asteroid 772 Tanete occults the 8.8-magnitude star HIP 9177 in Cetus at approximately 1:30 a.m. CST on December 14th for observers from the Gulf Coast of Texas north to Winnipeg in Canada. Browse http://www.asteroido...2_37331_Map.gif or see page 51 of the December issue of Sky & Telescope for additional details. For information on this year’s bright asteroids and upcoming asteroid occultation events, consult http://www.curtrenz.com/asteroids.html and http://asteroidoccultation.com/ respectively.
The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in magnitude from +2.1 to +3.4, on December 1st, 4th, 7th, 10th, 13th, 16th, 19th, 22nd, 24th, 27th, and 30th. On December 18th (December 19th UT) and December 21st (December 22nd UT), Algol is at minimum brightness for approximately two hours and is well-placed in the first half of the night for observers in North America. Consult page 51 of the December issue of Sky & Telescope for the times of the eclipses. For more on Algol, see http://stars.astro.i.../sow/Algol.html and http://www.solstatio...rs2/algol3.htm
Information on observing some of the more prominent Messier galaxies can be found at http://www.cloudynig...ur-astronomers/
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)
Notable carbon star for December: U Camelopardalis
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.