Sky & Telescope - December 2021 - 47

+30°
+40°
+10°
+20°
0°
-10°
LIBRA
Mars
Dec 30
SCORPIUS
-30°
-40°
10 am
8 am
6 am
4 am
2 am
Midnight
Antares
Spica
CORVUS
HYDRA
CANIS
MAJOR
10 pm
LOCAL TIME OF TRANSIT
8 pm
CAPRICORNUS
Fomalhaut
6 pm
4 pm
7 Venus
Mercury
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.
light. That's close enough that both
objects can be seen together in the field
of view provided by ordinary binoculars.
Interesting, sure. But worth braving the
chill air of a December night? Perhaps
not. However, your binos or (even better)
a small telescope might reveal a
bonus event. Look closely, and if your
timing is right, you may catch the glint
of 3.5-magnitude Eta (η) Leonis hovering
just off the dark lunar limb.
The specifics of what you have a
chance to see depend on where you are.
Skywatchers on the East Coast get to
witness a complete occultation. They'll
see the Moon's bright edge covering Eta,
and then later witness the star pop out
Dusk, Dec 31
45 minutes after sunset
Jupiter
δ
CAPRICORNUS
Saturn
α
β
Mercury
Venus
Looking Southwest
from behind the dark limb. For observers
in New York City, for example, the
stellar eclipse begins at 9:50 p.m. EST
and wraps up at 10:52 p.m. People at
locations in the central part of the
continent will miss the coverup but will
catch the star's reemergence. From Des
Moines, Iowa, Eta's return occurs at
about 9:48 p.m. CST. For those in the
western half of the U.S. and Canada,
you'll just get to see the star attractively
positioned to the right of the lunar disk.
TUESDAY, DECEMBER 28
At last, here's an event that has nothing
to do with the Moon. Instead, we can
appreciate the rise and fall of the two
innermost planets. The one gaining elevation
is Mercury, and the one losing
ground is Venus. At dusk today they're
at their closest. The two planets will be
separated by roughly 4¼° but are worlds
apart when it comes to brightness -
Mercury shines at magnitude -0.7, but
Venus is 33 times brighter, at magnitude
-4.5. If you're struggling to find
Mercury, simply wait a couple of nights.
On the 30th and 31st, its elevation will
match that of Venus, though they'll be
farther apart than on the 28th. This is
the last notable event of Venus's current
tThese scenes are drawn for near the middle
of North America (latitude 40° north, longitude
90° west). European observers should move
each Moon symbol a quarter of the way toward
the one for the previous date; in the Far East,
move the Moon halfway. The blue 10° scale bar
is about the width of your fist at arm's length.
For clarity, the Moon is shown three times its
actual apparent size.
evening apparition. Indeed, this might
be one of the last times you see it for a
while. Venus is in conjunction with the
Sun on January 9th, soon after which
it reappears at dawn in its guise as the
Morning Star.
FRIDAY, DECEMBER 31
Try getting up early to make the most of
the final day of 2021. Your efforts will
be amply rewarded with a pretty dawn
conjunction featuring the Moon (of
course), Mars, and Antares. The trio
form a pleasingly symmetrical triangle
in the southeast during morning
twilight, with the thin lunar crescent
sitting some 3½° from Mars and about
3° from Antares. The Red Planet, still
fresh from its October solar conjunction,
shines a relatively faint magnitude
1.5. That's slightly dimmer than nearby
Antares, but as the planet's apparition
progresses, it will slowly brighten. (The
next Mars opposition doesn't occur
until December 2022.) By mid-April,
Mars should be a good match for 1stmagnitude
Antares, but by then the
planet's eastward drift will have carried
it far from the star and into the constellation
Aquarius. For now, you can
appreciate their similar hues while the
peachy pair are near each other. You can
also see why the name Antares means
" like Ares " in ancient Greek, remembering
that Greek Ares = Roman Mars.
¢ Consulting Editor GARY SERONIK
enjoys each and every full Moon - even
the small ones.
sk yand tele scope .o r g * DECEMBER 2021
47
Sirius
Rigel
ERIDANUS
16h
14h
HERCULES
BOÖTES
Arcturus
VIRGO
27
LEO
Regulus
24
CANCER
Betelgeuse
Procyon
ORION
EQUATOR
Neptune
CETUS
Dec 10
AQUARIUS
Jupiter Saturn
AQUILA
TAURUS
12h
10h
8h
GEMINI
Castor
Pollux
Dec
18 - 19
Pleiades
ARIES
Uranus
14
PISCES
6h
4h
2h
0h
PEGASUS
+20°
+10°
0°
-10°
22h
RIGHT ASCENSION
CYGNUS
20h
+30°
+40°
Vega
DECLINATION
I
L
C
E
C
I
T
P

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Sky & Telescope - December 2021

Table of Contents for the Digital Edition of Sky & Telescope - December 2021