My first Magazine Sky & Telescope - 01.2019 | Page 46

JANUARY 2019 OBSERVING
Planetary Almanac
PLANET VISIBILITY Mercury: visible at dawn through the 3rd • Venus: visible at dawn
all month • Mars: visible at dusk, sets before midnight • Jupiter: visible at dawn all month •
Saturn: visible at dawn after the 23rd
Mercury
Jan 1
31
21
11
January Sun & Planets
Venus
Date
Declination Elongation Magnitude Diameter Illumination Distance
43.5 m –23° 04′ — –26.8 32′ 32″ — 0.983
20 h 52.0 m –17° 36′ — –26.8 32′ 28″ — 0.985
32.1 m –23° 09′ 16° Mo –0.4 5.2″ 89% 1.296
11 18 h 37.8 m –24° 10′ 12° Mo –0.6 4.8″ 95% 1.386
21 19 h 46.7 m –23° 00′ 6° Mo –0.9 4.7″ 99% 1.422
31 20 h 56.9 m –19° 25′ 2° Ev –1.5 4.8″ 100% 1.403
27.0 m –15° 15′ 47° Mo –4.6 26.3″ 47% 0.635
11 16 h 08.2 m –17° 31′ 47° Mo –4.5 23.5″ 53% 0.711
21 16 h 52.7 m –19° 25′ 46° Mo –4.4 21.2″ 57% 0.786
31 17 h 39.8 m –20° 43′ 45° Mo –4.3 19.4″ 62% 0.861
59.3 m –0° 24′ 80° Ev +0.5 7.4″ 87% 1.261
16 0 h 36.0 m +3° 54′ 75° Ev +0.7 6.7″ 88% 1.389
31 1 h 13.3 m +8° 03′ 69° Ev +0.9 6.2″ 89% 1.518
40.3 m –21° 32′ 28° Mo –1.8 31.8″ 100% 6.194
17 h 05.2 m –22° 13′ 53° Mo –1.9 33.6″ 99% 5.872
48.2 m –22° 29′ 1° Ev +0.5 15.0″ 100% 11.043
31 19 h 03.1 m –22° 11′ 26° Mo +0.6 15.2″ 100% 10.935
Uranus 16 1 h 46.2 m +10° 24′ 93° Ev +5.8 3.6″ 100% 19.783
Neptune 16 23 h 03.2 m –7° 07′ 49° Ev +7.9 2.2″ 100% 30.576
Sun
Mercury
31
Mars
Venus
1
16
Jupiter
Mars
31
Saturn
The table above gives each object’s right ascension and declination (equinox 2000.0) at 0 h Universal Time on selected dates,
and its elongation from the Sun in the morning (Mo) or evening (Ev) sky. Next are the visual magnitude and equatorial diameter.
(Saturn’s ring extent is 2.27 times its equatorial diameter.) Last are the percentage of a planet’s disk illuminated by the Sun and
the distance from Earth in astronomical units. (Based on the mean Earth–Sun distance, 1 a.u. is 149,597,871 kilometers, or
92,955,807 international miles.) For other dates, see skyandtelescope.com/almanac.
10"
PLANET DISKS have south up, to match the
view in many telescopes. Blue ticks indicate the
pole currently tilted toward Earth.
18 h
16 h
14 h
12 h
RIGHT ASCENSION
Vega
VIRGO
OPHIUCHUS
CANCER
25
LIBRA
–10°
Mercury
Saturn
Jan 1
31 Venus
SAGITTARIUS
SCORPIUS
–40°
10 am
28
GEMINI
4 h
2 h
Pleiades
EC
Spica
LI
I
PT
16
Betelgeuse
TAURUS
PEGASUS
Uranus
Mars
EQUATOR
Neptune
+40°
+30°
+20°
ERIDANUS
2 am
10 pm
–10°
10
–30°
Fomalhaut
8 pm
LOCAL TIME OF TRANSIT
6 pm
4 pm
2 pm
The Sun and planets are positioned for mid-January; 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). “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.
44
JA N UA RY 2 019 • SK Y & TELESCOPE
0°
CAPRICORNUS
CANIS
MAJOR
Midnight
CETUS
10°
AQUARIUS
Rigel
Jupiter
4 am
CYGNUS
ARIES
Sirius
CORVUS
HYDRA
6 am
22 h
13
ORION
C
0 h
PISCES
Jan
20– 21
Antares
8 am
6 h
Procyon
0°
–30°
Castor
Pollux
Regulus
+10°
AQUILA
8 h
LEO
Arcturus
HERCULES
+20°
10 h
BOÖTES
+30°
h
1
16
+40°
h
1
Saturn
Neptune
h
1
Jupiter
Uranus
h
1
31
16
h
1
1
h
1
31
16
Right Ascension
–40°