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 The Curtiss Cross, an X-shaped clair-obscure illumination effect located between the craters Parry and Gambart, is predicted to be visible at 10:13
12/2 Venus is at its greatest illuminated extent at 0:00
12/3 Mars is at eastern quadrature at 1:00; the Moon is 7.2 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 9:00; the Moon is 3.4 degrees north-northeast of Venus at 21:00
12/4 The earliest end of evening twilight at 40 degrees north takes place today; the Moon is 1.5 degrees south-southwest of the dwarf planet/asteroid 1 Ceres at 13:13
12/5 The Moon is 1.8 degrees north-northeast of Mercury at 22:00
12/6 The Moon is 3.4 degrees north-northeast of Jupiter at 15:00; Mercury is stationary in right ascension, with direct (eastward) motion to resume, at 20:00; Mercury is stationary in longitude at 21:00; the Moon is 8.4 degrees north-northeast of the first-magnitude star Antares (Alpha Scorpii) at 23:00
12/7 The earliest sunset at latitude 40 degrees north occurs today; New Moon (lunation 1187) occurs at 7:20; Mars (magnitude +0.1) is 0.04 degree north-northwest of Neptune (magnitude +7.9) at 15:00; asteroid 433 Eros (magnitude +9.7) is at opposition at 17:00
12/8 Asteroid 40 Harmonia (magnitude +9.4) is at opposition at 19:00
12/9 The Moon is 1.1 degrees north of Saturn, with an occultation taking place in far northern China and southeastern Russia, at 5:00; the Moon is at its southernmost declination (-1.54 degrees) for the year at 12:00; Mercury is at its greatest latitude north of the ecliptic plane (7.0 degrees) at 14:00
12/10 The Moon is 0.73 degree north of Pluto, with an occultation taking place in the Aleutian Islands, northern Micronesia, eastern and southeastern Russia, Japan, eastern Mongolia, and northeastern China at 4:00; the Moon is at the descending node (longitude 297.2 degrees) at 18:00
12/12 The Moon is at apogee, subtending 29' 29" from a distance of 405,177 kilometers (251,765 miles), at 12:25
12/13 Mars and Uranus are at heliocentric conjunction (a heliocentric longitude of 31.2 degrees) at 20:00
12/14 The peak of the Geminid meteor shower (100 to 120 per hour) occurs at 13:00; the Moon is 2.8 degrees south-southeast of Neptune at 16:00; the Moon, Mars, and Neptune lie within a circle of diameter 4.89 degrees at 20:00; the Lunar X (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 22:40
12/15 The Moon is 3.4 degrees south-southeast of Mars at 2:00; sunrise takes place at the isolated lunar mountain Mons Pico at 2:23; Mercury is at greatest elongation western elongation (21.0 degrees) at 12:00; First Quarter Moon occurs at 11:49; sunrise takes place at the isolated lunar mountain Mons Piton at 17:30
12/18 The Moon is 4.7 degrees south-southeast of Uranus at 7:00; the Sun enters the constellation of Sagittarius (ecliptic longitude 266.60 degrees) at 14:00
12/20 Jupiter is 5.0 degrees north of Antares at 2:00; the Moon is 8.4 degrees south-southeast of the bright open cluster M45 (the Pleiades or Subaru) in Taurus at 16:00
12/21 The Moon is 1.6 degrees north-northwest of the first-magnitude star Aldebaran (Alpha Tauri), at 7:00; Mercury (magnitude -0.4) is 0.83 degree north-northeast of Jupiter (magnitude -1.8) at 20:00; the Sun’s longitude is 270 degrees and winter solstice in the northern hemisphere occurs at 22:23
12/22 Mercury (magnitude -0.4) is 6.0 degrees north-northeast of Antares at 13:00; Full Moon (known as the Before Yule, Cold, Long Nights, and Oak Moon) occurs at 17:49; the Moon is 3.1 degrees south of the bright open cluster M35 in Gemini at 21:00
12/23 The Moon is at its northernmost declination for the year at 12:00; Jupiter is 5.2 degrees north of Antares at 19:00
12/24 The Moon is 10.6 degrees south of the first-magnitude star Castor (Alpha Geminorum) at 3:00; the Moon is 7.0 degrees south of the first-magnitude star Pollux (Beta Geminorum) at 7:00; the Moon is at perigee, subtending 33' 06" from a distance of 361,062 kilometers (224,353 miles), at 9:49; the Moon is at the ascending node (longitude 116.9 degrees) at 11:55
12/25 The Moon is 0.33 degree south-southwest of the bright open cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 5:00; the equation of time equals 0 (i.e., mean solar time equals apparent solar time) at 10:00
12/26 Venus is at perihelion (0.7185 astronomical units from the Sun) at 16:00; the Moon is 2.4 degrees north-northeast of the first-magnitude star Regulus (Alpha Leonis) at 18:00
12/27 Asteroid 3 Juno is stationary at 15:00; Venus (magnitude -4.5) is 3.0 degrees south-southwest of the dwarf planet/asteroid 1 Ceres (magnitude +8.9) at 10:30
12/28 Asteroid 6 Hebe (magnitude +8.4) is at opposition at 2:00
12/29 Last Quarter Moon occurs at 9:34
12/30 The Moon is 7.3 degrees north-northeast of Spica at 15:00
12/31 The Curtiss Cross, an X-shaped clair-obscure illumination effect located between the craters Parry and Gambart, is predicted to be visible at 0:51
Tycho Brahe, Johannes Kepler, Isaac Newton, E. E. Barnard, and Arthur Eddington were born in December.
Giovanni Cassini discovered the Saturnian satellite Rhea on December 23, 1672. Nicolas Louis de Lacaille discovered NGC 2070 (the Tarantula Nebula) on December 5, 1751. The bright spiral galaxies M81 and M82 in Ursa Major were discovered by Johann Bode on December 31, 1774. William Herschel discovered the galaxy pair NGC 3166 and NGC 3169 in Sextans on December 19, 1783. Caroline Herschel discovered Comet 35P/Herschel-Rigoliet on December 21, 1788. Caroline Herschel discovered Comet C/1791 X1 (Herschel) on December 15, 1791. The Jovian satellite Himalia was discovered by Charles Perrine on December 3, 1905. Audouin Dolfus discovered the Saturnian satellite Janus on December 15, 1966. The Saturnian satellite Epimetheus was discovered by Richard Walker on December 18, 1966.
The peak of Geminid meteor shower occurs on the morning of December 14th and is not adversely affected by moonlight from a slim waning crescent Moon. 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. Geminid meteors travel at a relatively slow speed of 35 kilometers per second (22 miles per second). An article on this year’s Geminids can be found on pages 48 and 49 of the December 2018 issue of Sky & Telescope. The Ursids, a normally minor meteor shower, peak on the morning of December 22nd but are severely compromised by a Full Moon. The radiant is located close to Kochab (Beta Ursa Minoris), some 15 degrees from the north celestial pole. See http://earthsky.org/...-guide#geminids and https://www.imo.net/...urces/calendar/ for additional information on the Geminids and https://earthsky.org...winter-solstice and https://www.imo.net/...urces/calendar/ for more on the Ursids.
Information on Iridium satellite flares and passes of the ISS, the Tiangong-2, the X-37B, the HST, and other satellites can be found at http://www.heavens-above.com/
The Moon is 23.1 days old, is illuminated 41.3%, subtends 31.5 arc minutes, and is located in Virgo on December 1st at 0:00 UT. 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 (+21.4 degrees) for the month on December 23rd and greatest southern declination (-21.5 degrees) on December 9th. Longitudinal libration is at a maximum of +5.4 degrees on December 5th and a maximum of +6.5 on December 31st. It’s at a minimum of -6.7 degrees on December 19th. Latitudinal libration is at a maximum of +6.8 degrees on December 18th and a minimum of -6.6 degrees on December 3rd. New Moon occurs on December 7th. The Moon is at apogee (a distance of 63.53 Earth-radii) on December 13th and at perigee (a distance of 56.61 Earth-radii) on December 24th. The Moon occults Saturn on December 8th and Pluto on December 9th from certain parts of the world. 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. Browse http://www.cambridge...ft/the_moon.htm and http://www.shallowsky.com/moon/ for information on various lunar features. 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 +3.0, 9.6", 6% illuminated, 0.70 a.u., Libra), Venus (magnitude -4.9, 40.7", 26% illuminated, 0.41 a.u., Virgo), Mars (magnitude 0.0, 9.3", 86% illuminated, 1.01 a.u., Aquarius), Jupiter (magnitude -1.7, 31.1", 100% illuminated, 6.34 a.u., Scorpius), Saturn (magnitude +0.5, 15.2", 100% illuminated, 10.91 a.u., Sagittarius), Uranus (magnitude +5.7, 3.7", 100% illuminated, 19.29 a.u. on December 16th, Aries), Neptune (magnitude +7.9, 2.3", 100% illuminated, 30.10 a.u. on December 16th, Aquarius), and Pluto (magnitude +14.3, 0.1", 100% illuminated, 34.58 a.u. on December 16th, Sagittarius).
During the evening, Mars and Neptune can be found in the south, Saturn in the southwest, Uranus in the southeast. Uranus is in the west at midnight. In the morning, Mercury, Venus, and Jupiter are located in the southeast.
Memorable conjunctions of Mars and Neptune and Jupiter and Mercury occur this month on December 7th and December 21st respectively.
Mercury returns to the morning sky in a somewhat favorable apparition for observers in the northern hemisphere. Mercury has an angular diameter of nine arc seconds and is one-quarter illuminated on December 5th. It spans just seven arc seconds and is almost 50% illuminated on December 11th. Mercury is stationary in right ascension and in longitude on December 6th, is at its greatest heliocentric latitude north on December 9th, and is at greatest elongation west on December 15th. During the second half of the month, Mercury sinks farther into morning twilight. The speediest planet is located 0.9 degree north of Jupiter on the morning of December 21st, when it is just six arc seconds in apparent size and 76% illuminated, and six degrees north of Antares on December 22nd.
Venus reaches its greatest illuminated extent on December 2nd and shines brilliantly at magnitude -4.9. On the morning of December 3rd, the waning crescent Moon passes about five degrees to the north of the planet. Spica lies about seven degrees to the right of the pair. Venus departs Virgo and enters Libra on December 13th. On December 26th, the brightest planet is at perihelion. Venus fades slightly to magnitude -4.6 and shrinks to an angular diameter of 26.6 arc seconds but increases in illumination to 47% by December 31st.
Mars begins the month at a brightness of 0.0 magnitude and a rather tiny 9.3 arc seconds in apparent size. The Red Planet and Neptune come to an unusually close conjunction on December 7th. Mars is four degrees south of the nearly First Quarter Moon on the night of December 14th. It moves from Aquarius into Pisces on December 21st. As the year ends, Mars sets shortly before midnight local time and is located a few degrees southeast of the Circlet of Pisces asterism. It shines at magnitude +0.4, subtends 7.5 arc seconds, is illuminated 87%, and lies at a distance of 1.25 astronomical units.
Jupiter rises about one hour before the Sun on December 12th. It enters Ophiuchus at mid-month and passes five degrees from Antares on December 20th. Jupiter and Mercury are in conjunction on December 21st. Click on http://www.skyandtel...watching-tools/ 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 2018 issue of Sky & Telescope.
Saturn lies about ten degrees above the southwestern horizon forty-five after sunset on December 1st. On December 8th, Saturn is just seven degrees in altitude at that time. A two-day old waxing crescent Moon is located three degrees to the lower right of the Ringed Planet on that evening. Saturn disappears into the glare of the Sun by mid-December on its way to solar conjunction in early January.
Uranus exits Aries and enters Pisces on December 3rd. It sets after midnight local time. In early December, Uranus is positioned 1.6 degrees north-northeast of the fourth-magnitude star Omicron Piscium. The seventh planet lies 1.3 degrees north of that star at the end of the month. Uranus is 4.3 degrees north-northwest of the Moon on December 27th. Browse http://www.bluewater...anus_2018_1.pdf for a finder chart.
Neptune sets in the late evening. Neptune and Mars undergo an extremely close conjunction on December 7th. The two planets are separated by 3.6 degrees on December 1st. That distance decreases by approximately 0.6 degree daily. Neptune is positioned 23 arc minutes east-northeast of Mars on the evening of December 6th. At 9:08 a.m. EST on December 7th, Mars is just 2.2 arc minutes north of Neptune. On the evening of December 7th, Neptune lies 16 arc minutes southwest of the Red Planet. The sixth-magnitude star 81 Aquarii is 12 arc minutes to the north of Mars. The Moon passes three degrees south of the eighth planet on December 14th. Neptune passes 15 arc minutes due south of 81 Aquarii on the evening of December 24th. A finder chart is posted http://www.bluewater...tune_2018_1.pdf
Additional online finder charts for Uranus and Neptune can be found at http://www.nakedeyep....com/uranus.htm and http://www.nakedeyep...com/neptune.htm and also at https://www.skyandte...EB_UrNep18.pdf and on pages 48 and 49 of the September 2018 issue of Sky & Telescope.
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 46P/Wirtanen heads northeastward through Eridanus, Taurus, and Auriga during December. It will pass within 7.2 million miles of the Earth on December 16th and may reach a brightness of fourth magnitude, making it potentially visible to the unaided eye from a dark site. At the time of its closest approach, the periodic comet will be located between the bright open clusters Melotte 25 (the Hyades) and M45 (the Pleiades). Finder charts can be found online at http://www.cometwatc...t-46p-wirtanen/ and http://wirtanen.astr...s/Full_view.png and on page 50 of the November 2018 issue of Sky & Telescope. Comet 38P/Stephan-Oterma is situated approximately ten degrees from Castor and Pollux during the first half of the month. This periodic comet is closest to the Earth on December 17th and may reach ninth magnitude. Click on http://www.cometwatc...18/10/38p_2.jpg for a finder chart. Visit http://cometchasing.skyhound.com/ and http://www.aerith.ne...t/future-n.html for information on comets that are visible this month.
A list of the closest approaches of comets to Earth is posted at http://www.cometogra.../nearcomet.html
Asteroid 3 Juno glides northwestward the constellation of Eridanus this month. The main belt asteroid dims from magnitude +7.6 to magnitude +8.2 during December. Juno is a bit unusual in that its orbit is inclined 13 degrees to the ecliptic. Asteroid 6 Hebe makes its closest approach to the Earth on December 20th and shines at magnitude +8.4 when it reaches opposition on December 28th. The fifth brightest asteroid passes south of the open cluster NGC 2244 in Monoceros on December 20th and northeast of the binary star 8 Monocerotis on December 25th. A finder chart is featured on page 50 of the December 2018 issue of Sky & Telescope. Other bright asteroids reaching opposition this month include 433 Eros (magnitude +9.7) on December 7th in Camelopardalis and 40 Harmonia (magnitude +9.4) on December 8th in Taurus. 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.
Various events taking place within our solar system are discussed at http://www.bluewater...ed-4/index.html
The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in magnitude from +2.1 to +3.4, on December 3rd, 5th, 8th, 11th, 14th, 17th, 20th, 23rd, 26th, 28th, and 31st (UT dates). Algol is at minimum brightness for approximately two hours and is well-placed for observers in North America on the nights of December 2nd (centered at 9:53 p.m. EST), December 5th (centered at 6:42 p.m. EST), and December 22nd (centered at 11:36 p.m. EST). Consult page 51 of the December 2018 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...ars2/algol3.htm
Data on current supernovae can be found at http://www.rochester...y.org/snimages/
Information pertaining to observing some of the more prominent Messier galaxies can be found at http://www.cloudynig...ur-astronomers/
Author Phil Harrington offers an excellent freeware planetarium program for binocular observers known as TUBA (Touring the Universe through Binoculars Atlas), which also includes information on purchasing binoculars, at http://www.philharrington.net/tuba.htm
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 19, 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.