TAURUSAldebaranPleiadesHyades
a¡Path of
Comet PANSTARRSJan 161116212631N2°EComet PANSTARRS (C/2016 R2)15"
January 10, 5:25 A.M. ESTJupiterIoEuropaSWJupiter’s moons on the verge of eclipse42 ASTRONOMY • JANUARY 2018
COMETSEARCH
Comet PANSTARRS (C/2016 R2)
shares the sky with dozens of
deep-sky gems sprinkled across
the winter Milky Way. It glides
past the head of Taurus the
Bull during January as it heads
north, and it remains on view for
most of the night.
A small ball of dust and ice,
PANSTARRS simultaneously is out
of place and at home. Visually it
appears much like a 10- or 11th-
magnitude elliptical galaxy, at
odds with the sparkling open
star clusters and amorphous gas
clouds in this area. Yet the fin-
gers of obscuring dust and gas in
the background are every bit like
the nursery that gave birth to our
solar system and its shell of com-
ets, the Oort Cloud.C/2016 R2 should be within
reach of 4-inch telescopes under
a dark sky. From the suburbs,
you’ll likely need a 10-inch scope
to spot it. On a positive note, it
should be compact and well-
defined, making it a good target
at medium or high power.
Astroimagers will want to
capture PANSTARRS in this pho-
togenic region near the Hyades
and Pleiades (M45) star clusters.
Deeper exposures also will record
the wisps of galactic dust and gas
that thread through the Milky
Way’s outer spiral arm. Imagers
should skip the first few days of
January and the month’s final
week when the Moon interferes.
Although the first few
months of 2018 don’t showA snowball in the winter sky
EVENING SKY MIDNIGHT MORNING SKY
Uranus (south) Uranus (west) Mercury (southeast)
Neptune (southwest) Mars (southeast)
Jupiter (south)
Saturn (southeast)
WHEN TO VIEW THE PLANETS
— Continued from page 37
world through a telescope. A
view at medium power reveals
Uranus’ 3.5"-diameter disk and
distinct blue-green color.
The rest of the visible plan-
ets congregate in the morning
sky. Mars already has begun its
long trek toward an outstand-
ing opposition in July. Or, more
accurately, Earth has started to
catch up to Mars as our planet
speeds around the Sun a bit
more quickly than its outer
neighbor. The Red Planet will
linger in the morning sky for
several months, at first growing
slowly in brightness and appar-
ent size as Earth draws closer.
The snail’s pace will pick up
this spring as Mars gets ready
for a spectacular summer show.
On January 1, Mars stands
2.6° west of Jupiter and the
from the Sun and invisible.
They haven’t been this close
and visible since January 1998.
A telescope shows both
planets in a single low-power
field of view. Mars spans 5"
compared with Jupiter’s 34".
Yet Jupiter lies three times far-
ther away, a testament to its
status as a giant planet.
Just four mornings after
this fine conjunction, a waning
crescent Moon joins the two in
a stunning predawn display.
On January 11, Mars stands
4.6° south of the Moon whilepair rises more than four
hours before the Sun. Mars
shines at magnitude 1.5 while
Jupiter dazzles at magnitude
–1.8. The two straddle Libra’s
second-brightest star, magni-
tude 2.8 Zubenelgenubi
(Alpha [α] Librae), which
itself is a fine double.
The planets shift eastward
relative to the background
stars during January, with
Mars moving faster in its inner
orbit. Watch every morning as
their positions change relative
to Zubenelgenubi and to each
other. On the 2nd, Mars passes
0.6° north of Alpha. And on
the 7th, the two solar system
worlds stand just 16' apart.
This is the closest they’ve been
since September 2004, but they
were then just a few degreesJupiter lies 2.1° west of the
Red Planet. Use binoculars
for a close-up view or just
enjoy the scene with your
naked eye.
Although the planets rise
earlier with each passing
morning, the gap between the
two grows wider. Slowpoke
Jupiter remains in Libra all
month, while Mars speeds
across that constellation and
enters Scorpius on the 31st.
Having brightened to magni-
tude 1.2, the Red Planet
stands 9° northwest of themuch promise for bright com-
ets, things should pick up this
summer. And if predictionshold, Comet 46P/Wirtanen
could become visible to the
naked eye next autumn.This first-time visitor to the inner solar system should glow around 10th
magnitude as it travels between the Hyades and Pleiades star clusters.On January 10, Io and Europa simultaneously disappear into Jupiter’s
shadow just a few minutes after the scene depicted here.