Post by Chicago Astronomer - Astro Joe on Dec 8, 2007 6:13:30 GMT -6
December 2007 Astronomical Data
12/1 Last Quarter Moon occurs at 12:44; Saturn is 2 degrees north
of the Moon at 13:00
12/4 Mercury is at the descending node today
12/5 A minimum lunar libration of 6.1 degrees occurs at 1:00
12/6 Venus is 7 degrees north of the Moon at 1:00; the Moon is at
apogee, subtending 29'33" from a distance of 406,235 kilometers, at
16:53
12/8 The earliest sunset of 2007 at 40 degrees north latitude
occurs today
12/9 New Moon (lunation 1051) occurs at 17:40; a maximum lunar
libration of 6.8 degrees occurs at 23:00
12/12 The Moon is 0.4 degrees south of asteroid 4 Vesta, with an
occultation taking place in most of South America and New Zealand, at
21:00
12/14 A minimum lunar libration of 6.4 degrees occurs at 12:00; the
peak of the Geminid meteor shower (100 per hour) occurs at 17:00;
Neptune is 0.7 degree north of the Moon, with an occultation taking
place in part of Antarctica, the southern tip of South America, and
South Africa, at 18:00
12/15 Mercury is at aphelion today
12/16 The Moon is 1.0 degree north of the asteroid 2 Pallas, with an
occultation taking place in northwestern Canada, the eastern portion
of Siberia, and Hawaii, at 1:00; Uranus is 2 degrees south of the
Moon at 18:00
12/17 First Quarter Moon occurs at 10:18; Mercury is in superior
conjunction with the Sun at 15:00
12/19 Mars is 88,165,000 kilometers from the Earth, its closest
approach until the year 2016, at 0:00; a maximum lunar libration of
6.8 degrees occurs at 4:00
12/20 Saturn is stationary at 12:00
12/21 Pluto is in conjunction with the Sun at 0:00; the Moon is 1.0
degree north of the bright open cluster M45 (the Pleiades) in Taurus
at 23:00
12/22 Venus is at its greatest heliocentric latitude north today; the
winter solstice occurs at 6:08; the Moon is at perigee, subtending
33'07" from a distance of 360,815 kilometers, at 10:14
12/23 The peak of the Ursid meteor shower (10 per hour) occurs at
1:00; a minimum lunar libration of 6.5 degrees occurs at 1:00;
Jupiter is in conjunction with the Sun at 6:00
12/24 The Full Moon (known as the Before Yule, Cold, Long Nights, and
Oak Moon) occurs at 1:16; Mars is 0.9 degree south of the Moon, with
an occultation taking place in northwestern Canada, Alaska, the
Arctic, northern Russia, eastern Europe, and northeastern Great
Britain, at 3:00; Mars (magnitude -1.6, apparent size 15.9") is at
opposition at 20:00
12/26 The Moon is 0.4 degree north of the bright open cluster M44
(the Beehive Cluster or Praesepe) in Cancer at 12:00
12/27 A maximum lunar libration of 7.0 degrees occurs at 14:00
12/28 The Moon is 0.6 degree south of the first magnitude star
Regulus (Alpha Leonis) at 5:00; Saturn is 3 degrees north of the Moon
at 22:00
12/30 Comet 8P/Tuttle passes within a degree of the spiral galaxy M33
in Triangulum at 5:00
12/31 Last Quarter Moon occurs at 7:51
The Moon occults the Pleiades before dusk on December 21, the longest
night of the year. See www.lunar-
occultations.com/iota/pleiades/1221pleiades.htm for additional
information on the occultation. A favorable libration on December 23
allows the summit of Mount Clementine, the most easily visible
feature on the farside of the Moon, to be seen for a total of four
nights. The Moon is 21.0 days old and is located in Leo on December
1 at 0:00 UT. It attains its greatest northern declination (+28
degrees) for the month on December 23 and its greatest southern
declination (-28 degrees) for the month on December 10. Times and
dates for the lunar crater light rays predicted to occur this month
are available at www.lunar-occultations.com/rlo/rays/rays.htm
Brightness, apparent size, illumination, distance from the Earth in
astronomical units, and location data for the planets and Pluto on
December 1: Mercury (-0.8 magnitude, 4.9", 97% illuminated, 1.4 a.u.,
Libra), Venus (-4.2 magnitude, 17.8", 66% illuminated, 0.9 a.u.,
Virgo), Mars (-1.3 magnitude, 15.1", 97% illuminated, 0.6 a.u.,
Gemini), Jupiter (-1.8 magnitude, 31.8", 100% illuminated, 6.2 a.u.,
Ophiuchus), Saturn (0.7 magnitude, 18.1", 100% illuminated, 9.2 a.u.,
Leo), Uranus (5.9 magnitude, 3.5", 100% illuminated, 20.2 a.u.,
Aquarius), Neptune (7.9 magnitude, 2.2", 100% illuminated, 30.6 a.u.,
Capricornus), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 32.4
a.u., Sagittarius).
Visibility of the classical planets at mid-month for observers at 40
degrees north: Mars is in the evening sky in the east, in the
southern sky at midnight, and in the west in the morning; Saturn is
in the east at midnight and the southwest in the morning; and Venus
in the southeast in the morning.
Since it reaches superior conjunction on December 17, Mercury is a
difficult target this month.
Venus rises just prior to 4:00 a.m. on December 1. The first
magnitude star Spica, Venus, and the Moon form a triangle in Virgo on
the morning of December 5. Venus enters Libra on December 12. It
lies between Alpha and Beta Librae on December 19. Venus shrinks in
apparent size from 18 to 15" while its disk waxes in illumination
from 66 to 76%.
Mars is very well placed for northern-hemisphere observers during
December. It's positioned within 20 degrees of the zenith, as far
north as it ever gets, every night for a minimum of two hours. Mars
is less than half a degree north of the third magnitude star Epsilon
Geminorum and shines with a brilliance of magnitude -1.4, as bright
as Sirius, on the night of December 3. The Martian northern-
hemisphere vernal equinox takes place on December 9. Due to its
highly elliptical orbit, the Red Planet is closest to the Earth on
December 18. Mars is less than three degrees north of the bright
open cluster M35 in Gemini from December 21 to December 28. On the
night of December 23, it's just 2.5 degrees north of M35. Mars
reaches opposition on the night of December 24 and thus rises at
sunset, transits the meridian at midnight, and sets at sunrise. On
the night of opposition, Mars has a declination of 26 degrees and 46
arc minutes and at midnight is thus almost 77 degrees above the
southern horizon. Since the Martian day, or sol, is 37.4 minutes
longer than a terrestrial one, Martian surface features appear to
move 9.11 degrees to the west each day. Mare Sirenum is visible at
the beginning of the month at midnight, followed by Solis Lacus (the
Eye of Mars) and Sinus Meridiani at mid-month, and Syrtis Major when
the planet reaches opposition. Mars travels eleven degrees westward
during December but retrogrades back into the constellation of Taurus
on December 30. See the Mars Profiler at
www.skyandtelescope.com/observing/objects/javascript/mars for
a hemispherical map of Martian surface features and
www.skyandtelescope.com/observing/objects/javascript/mars_moons
/index.html for the positions of the faint Martian moons Phobos and
Deimos.
Jupiter enters Sagittarius on December 2. It slips out of view by
the second week of the month as it heads toward conjunction on
December 23.
Saturn rises shortly before midnight on December 1, at approximately
10:30 p.m. EST at midmonth, and at approximately 8:00 p.m. EST by
month's end. It is at quadrature on December 1. Saturn's ring tilt
angle is now only seven degrees. Titan (magnitude 8.5) is due north
of the planet on December 4 and December 20. It is due south of
Saturn on December 12 and December 28. Saturn's curious two-faced
satellite Iapetus is due west of the planet by the listed separations
on the following dates: December 2 (24"), December 8 (34"), December
14 (36"), December 20 (30"), December 26 (17"), and December 30
(6"). For further information on the five brightest satellites of
Saturn, browse
skytonight.com/observing/objects/javascript/3308506.html
Uranus is located just east of 81 and 82 Aquarii. By the end of
December, the planet's eastward progress takes it to within two
degees of the fourth magnitude star Phi Aquarii.
Neptune's retrograde motion increases throughout December. It's
located about two degrees south of fourth magnitude Iota Capricorni.
Since Pluto is in conjunction with the Sun on December 18, it is not
visible this month.
The coma of Comet 17P/Holmes continues to expand to momumental
proportions as the comet travels through western Perseus. The
historic comet will pass approximately 1.5 degrees to the northwest
of the open cluster NGC 1245 on the night of December 2 and a bit
more than 2 degrees to the west of the cluster on December 13.
Another periodic comet, Comet 8P/Tuttle, passes through Cassiopeia
during December. It is near NGC 281 (the Pacman Nebula) on the night
of December 22 but will be compromised by strong moonlight. The
parent comet of the Ursid meteor shower passes close to M33 on the
nights of December 29 and December 30. Comet 8P/Tuttle starts the
month shining at ninth magnitude and may brighten to fifth magnitude
at its peak.