Sky & Telescope - December 2024 - 47

+30°
+40°
+10°
+20°
0°
-10°
Mercury
SCORPIUS
-30°
-40°
10 am
8 am
6 am
4 am
2 am
Midnight
Antares
LIBRA
Spica
Dec 26
23
CORVUS
HYDRA
CANIS
MAJOR
Fomalhaut
10 pm
LOCAL TIME OF TRANSIT
8 pm
6 pm
Dec 5
CAPRICORNUS
4 pm
SAGITTARIUS
2 pm
-30°
-40°
The Sun and planets are positioned for mid-December; the colored arrows show the motion of each during the month. The Moon is plotted for evening
dates in the Americas when it's waxing (right side illuminated) or full, and for morning dates when it's waning (left side illuminated). " Local time
of transit " tells when (in Local Mean Time) objects cross the meridian - that is, when they appear due south and at their highest - at mid-month.
Transits occur an hour later on the 1st and an hour earlier at month's end.
that February date, Mars reaches
opposition (on January 16th, at 3h UT),
when it's at its biggest and brightest for
the current apparition.
SATURDAY, DECEMBER 14
Late this evening, look high overhead
to catch a nifty, three-piece alignment.
Strung out in a line are Aldebaran (the
brightest star in Taurus, the Bull), Jupiter,
and the full Moon. The alignment
is most perfect shortly after 11 p.m. EST,
though the Moon moves slowly enough
that you don't need to be terribly exact
here. Jupiter is about 7° from Aldebaran,
and the Moon is a little more than
7½° from Jupiter. Nice. Regular readers
of this column may recall the October
installment in which I noted that when
the full Moon appears near an outer
planet, that planet must be near opposition.
And so it is this time - Jupiter
Dawn, Dec 27 - 29
30 minutes before sunrise
Moon
Dec 27
SCORPIUS
Mercury
Antares
Moon
Dec 29
Moon
Dec 28
reached opposition on December 8th,
less than a week ago. When the Moon
swings by the planet next month, it will
be a 90%-illuminated waxing gibbous.
If you continue to watch as the night
of the 14th transitions into the morning
of the 15th, you'll see the Moon
approach to within just 25′ (roughly one
Moon diameter) of 1.7-magnitude Beta
(β) Tauri. The gap between the star and
the northern edge of the lunar disk is at
its minimum at around 3 a.m. (on the
15th) EST. Binoculars are very helpful
for this conjunction, as the overwhelming
glare from the Moon makes seeing
the star a bit tricky.
WEDNESDAY, DECEMBER 18
The month's closest conjunction occurs
in the predawn hours today. That's
when the waning gibbous Moon glides
just north of ruddy Mars. They rise
near each other on the evening of the
17th and remain close all night. But
it's at around 4:36 a.m. EST that they're
at their very closest and separated by
about 17′ as seen from mid-northern
latitudes, though the exact amount
depends on your location. The farther
north you are, the smaller the gap. For
example, from Edmonton, Alberta, less
than 12′ separates the Red Planet from
the Moon's southern limb. And from
the high Arctic and Greenland, the conjunction
becomes an occultation.
Despite the glare from an 89%-illuLooking
Southeast
minated Moon, you'll have no trouble
seeing Mars. It's less than a month
away from opposition and its closest
approach to Earth, so it shines gamely
tonight at magnitude -0.9 - just a half
magnitude shy of its peak brightness for
this apparition. This is another of those
events that binoculars don't help you see
so much as appreciate. The optical boost
enhances the color contrast between
peachy-orange Mars and the stark,
silvery-gray of the lunar surface.
SATURDAY, DECEMBER 28
Our final highlight for the month is a
dawn double-feature. First, look to the
southeast to catch the 6%-illuminated
waning crescent Moon a mere 45′ right
of 1st-magnitude Antares, in Scorpius.
This is another one of December's
" occultation elsewhere " conjunctions -
observers in Polynesia and the southern
half of South America are the ones in
the right spot this time.
Our second feature is the chance
to sight Mercury during its best dawn
apparition of 2024. The innermost
planet is a bit more than 8° left of
Antares. Mercury reached its greatest
elongation (22° west of the Sun) on the
25th (at 3h UT) and achieves an altitude
of 11° above the east-southeastern
horizon half an hour before sunrise,
where the little world shines at magnitude
-0.4. If mornings aren't your
thing, you'll get another shot at sighting
Mercury during the peak of its dusk
apparition in March.
¢ Consulting Editor GARY SERONIK has
been fascinated by the comings and goings
of the planets since he was a child.
sk yand tele scope .o r g * DECEMBER 2024
47
16h
14h
HERCULES
BOÖTES
Arcturus
VIRGO
LEO
20
Regulus
Mars
Jupiter
CANCER
Betelgeuse
Procyon
ORION
Sirius
Rigel
ERIDANUS
EQUATOR
Neptune
CETUS
AQUARIUS
8
Saturn
Venus
AQUILA
TAURUS
12h
10h
8h
GEMINI
Castor
Pollux
6h
Dec
14 - 15
Pleiades
Uranus
10
PISCES
ARIES
4h
2h
0h
PEGASUS
+20°
+10°
0°
-10°
22h
RIGHT ASCENSION
CYGNUS
20h
+30°
+40°
Vega
DECLINATION
C
E
C
I
T
P
I
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Sky & Telescope - December 2024

Table of Contents for the Digital Edition of Sky & Telescope - December 2024