Astronomy - USA (2020-04)

April 15, 4:30 A.M. EDT 30"

W

S

Ganymede’s

shadow Ganymede

Io

Jupiter

2°

E

N

Path of Comet

PanSTARRS

May 1

26

21

(^1611)
6
April 1
IC 342
a
CAMELOPARDALIS
42 ASTRONOMY • APRIL 2020
Jupiter gets a black eye
COMET SEARCH I A comet floats amid spirals
COME ENJOY the unhurried
pace of the telescopic Comet
PanSTARRS (C/2017 T2). Arcing
toward its close approach to the
Sun in the first week of May, its
9th-magnitude glow is visible in
a 4-inch scope from dark country
skies. Wait until midmonth for the
Moon to slide out of the way.
If you are considering a
Messier marathon, put T2 in the
first half of the night so it is not
lost in the haze low on the north-
ern horizon later on — and throw
in the spiral galaxy IC 342 as well.
Both objects are located in the
less-visited constellation of
Camelopardalis, but if you visual-
ize folding the Little Dipper
across Polaris, you will land smack
on magnitude 4.6 Gamma (γ)
Camelopardalis, the signpost
labeled on the chart.
T2 is brighter than M109 (in Ursa Major) and likely more compact and, hence, well defined. Nearby
IC 342 contrasts starkly because that large nearly face-on spiral has a lower surface brightness. The
galaxy’s diffuse light fades as you go to higher power, but T2 will keep giving and likely reveal a nearly
stellar core, with a dense shroud of dust enveloping the invisible nucleus beneath.
Comet PanSTARRS (C/2017 T2)
Jupiter. At magnitude 14.8, the
famous dwarf planet is a dif-
ficult challenge — within
reach of imagers but beyond
visual observers.
Jupiter’s appearance
through a telescope is stun-
ning. The broad disk spans 37"
at the start of the month and
grows to 41" by the end. It’s
only three months to opposi-
tion, and ardent Jupiter watch-
ers will want to record video
frames to capture the best
views of the planet. Visual
observers can easily catch the
dark equatorial belts strad-
dling the equator. Subtle dark
belts lie to their north and
south, along with smaller fea-
tures such as dark and white
spots that are carried along
with the strong winds in
Jupiter’s atmosphere. The
Great Red Spot makes regular
appearances as well.
Some of the most engaging
events in the night sky are the
repeated occultations and
eclipses of Jupiter’s four giant
moons: Io, Europa, Ganymede,
and Callisto. Here’s a sampling
of those you can catch — there
are many more each month.
Ganymede, the largest of
the four, casts its shadow onto
the northern regions of Jupiter
on April 15. The event is
already underway as Jupiter
rises, and ends at 5:52 a.m.
EDT. You can catch Europa
crossing in front of Jupiter on
April 19 beginning at 5:17 a.m.
EDT, and ending nearly three
hours later (after sunrise on
the eastern seaboard but still
under cover of darkness farther
west). The following morning,
April 20, Io’s shadow treks across
the jovian cloud tops starting at
4:43 a.m. EDT. The moon fol-
lows at 6 a.m., and it can be
tracked in darkness across the
western half of the U.S.
Sometimes two events occur
within minutes of each other,
adding to the excitement.
April 26 finds Ganymede reap-
pearing from behind Jupiter’s
southeastern limb soon after
5:20 a.m. EDT, just as
Europa’s shadow begins its
transit at 5:18 a.m. EDT at the
northeastern limb. Ganymede
takes over six minutes to fully
reappear, by which time
Europa’s shadow is easily vis-
ible as well.
As mentioned earlier,
Saturn rises with Mars on
April 1 at 4 a.m. local daylight
time, and nearly two hours
earlier April 30. It lies in west-
ern Capricornus and shines at
magnitude 0.7, brightening by
one-tenth of a magnitude by
April 30. Saturn stands 2°
north of a Last Quarter Moon
on April 15.
A telescope will easily
reveal the bright ring system
that dominates the view of the
planet. Their widest span at
SKY THIS MONTH
WHEN TO
VIEW THE
PLANETS
EVENING SK Y
Venus (west)
Uranus (west)
MORNING SK Y
Mercury (east)
Mars (southeast)
Jupiter (southeast)
Saturn (southeast)
Neptune (east)
— Continued from page 37
3 
easily visible asteroids traipse through Taurus
this month: Vesta, Metis, and Hygiea.
This visitor from the distant Oort Cloud could reach 8th magnitude this month as it
traverses the dim backdrop of Camelopardalis.
Observers get a great chance to see this gas giant’s moons in action during
April. You can watch Ganymede’s shadow traverse Jupiter’s northern cloud
tops on the 15th.