SKY THIS MONTH
Visible to the naked eye
Visible with binoculars
Visible with a telescope36 ASTRONOMY • DECEMBER 2019
December brings the
longest nights of the
year to people in the Northern
Hemisphere. Normally, that
would signal favorable condi-
tions for backyard observers.
But this year, all of the naked-
eye planets cluster near the
Sun in our sky, leaving a long
stretch of the night without any
bright solar system targets.
December’s highlight has to
be the dramatic lineup of plan-
ets in the early evening sky.
While Venus dominates the
view toward the southwest after
sunset, Saturn and Jupiter add
a lovely f lair to the scene early
this month. Uranus and
Neptune, which appear much
fainter than their closer cous-
ins, appear higher in the sky
and remain visible through the
late evening hours. Eventually,
the long nights end with fineviews of Mercury and Mars
before dawn.
Let’s start our tour soon
after the Sun sets December 1.
A quick look to the southwestreveals Jupiter, Venus, and
Saturn strung out across nearly
20° of sky. Jupiter hangs lowest,
standing just 7° above the hori-
zon 30 minutes after sundown.5°December 1, 1 hour after sunset
Looking southwestSAGITTARIUSJupiterSaturnVenusA delightful planetary alignment
Saturn, Venus, and Jupiter put on a stunning show in early December, though
the gas giants disappear within a few weeks. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLYDecember 2019
Gas giants bid a fond farewell
THE SOLAR SYSTEM’S CHANGING LANDSCAPE AS IT APPEARS IN EARTH’S SKY.
BY MARTIN RATCLIFFE AND ALISTER LINGIt still appears prominent
because it shines brightly at
magnitude –1.8. The giant
world sinks lower with each
passing day, however, and
disappears into the Sun’s glare
during December’s second
week on its way to solar con-
junction on the 27th.
Ve nu s fares far better. On
December 1, it shines at mag-
nitude –3.9 — seven times
brighter than Jupiter — from
a perch 8° to the giant planet’s
upper left. You’ll have to wait
for the sky to darken some
before you’ll be able to see
magnitude 0.6 Saturn, which
lies 11° to Venus’ upper left.
Ta rget Venu s w it h bi noc u-
lars December 2 and you’ll see
one of the sky’s finest globu-
lar clusters, 5th-magnitude
M22 in Sagittarius, less than
1° to the north. A telescopeA Geminid fireball
blazes through an
aurora’s glow above
Alaska’s Knik River
Area in 2017. This year,
the Geminid shower
peaks under a moonlit
sky. MATT SKINNER