WHEN TO
VIEW THE
PLANETS
EVENING SKY
Mercury (west)
MORNING SKY
Venus (east)
Mars (southeast)
Jupiter (south)
Saturn (south)
Uranus (east)
Neptune (southeast)Path of
Comet PanSTARRSNEJune 151719212325
27M (^1062) °
NGC 4449
γ
11
(^75)
1
3
67
65
60
59
58
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Y
M 109
URSA MAJOR
CANES
VENATICI
42 ASTRONOMY • JUNE 2020
Iapetus
Hyperion
Titan
Dione Rhea
Tethys Enceladus
Saturn
June 1 , 2 : 00 A.M. EDT 1 '
W
S
Iapetus at its brightest
COMET SEARCH I PanSTARRS pairings
THE FANTASTIC PHOTO OPS
of comet and deep sky continue,
and timing with the New Moon
couldn’t be better. In case you
didn’t get last month’s issue, on
May 22 and 23 Comet PanSTARRS
(C/2017 T2) joined the great
galaxies Messier 81 and 82. By
chance, during the Full Moon on
June 5, the comet floats through
the uninteresting bowl of the Big
Dipper, then it poses less than a
degree from M109 on the night
of the 16th. The Moon doesn’t
even rise until twilight begins —
what good luck.
T2 has just passed its peak
brightness but should still be
roughly 8th magnitude as it
shares the field with the grand
and picturesque bright spiral gal-
axy M106 on the night of the
23rd. Since you’re taking advantage of mild summer conditions by observing all night on the weekend of
the 27th, see the comet near NGC 4449 after moonset.
Visually these galaxy-comet duos deserve prolonged inspection. Notice how their shapes are differ-
ent. The galaxies are symmetrical ovals, whereas the comet will be quite lopsided with its bright, round-
edged coma on one side and a flat, diffuse fan of a tail on the other. Take your time, push the power past
150x on a 6-inch and 300x on a 12-inch scope. Although it makes the view darker, the larger image scale
allows your averted vision to pick out structure in both objects.
Imagers will be delighted by the difference between T2’s green coma and the pink-red color of the
galaxies’ star-forming regions. But will the comet’s white dust tail be long enough to drape across the
distant starlight of these island universes? Let us know.
Comet PanSTARRS (C/2017 T2)
axis widens to 41.6" by June 30,
nearly three times the minor
axis. Skirting the outer edge of
the rings is Enceladus, orbiting
every 1.4 days. At magnitude
11.9, it is tricky to spot against
the brilliance of the rings.
Farther from the rings are
Tethys, Dione, and Rhea, shin-
ing between 10th and 11th mag-
nitude, and orbiting with
periods from 1.9 to 4.5 days.
Titan, the brightest moon, orbits
every 16 days and shines at
magnitude 8.8. You’ll find it due
north of Saturn June 14 and 30,
and due south June 6 and 22.
More distant Iapetus varies
in brilliance between eastern
and western elongations. It’s
brightest (magnitude 10.2) 9'
due west of Saturn on June 1,
just a day after its western elon-
gation. At this position the
brighter of Iapetus’ two hemi-
spheres faces Earth. Throughout
June it tracks closer to Saturn
and reaches superior conjunc-
tion June 20, 54" north of
Saturn and near magnitude 11.
Mars rises soon after 2 A.M.
local time on June 1 and an
hour earlier by June 30. It’s
located in Aquarius, brighten-
ing from magnitude 0 to –0.5 in
the pre-dawn sky this month.
The Red Planet is now only four
months away from opposition.
The best time to view it is in the
hour before dawn. At 4 A.M.^
local time, Mars stands only 20°
high on June 1, but 30° high at
the same time on June 30 —
higher than its 2018 opposition.
Mars tracks rapidly east
across eastern Aquarius this
month. On June 1, it is less than
3° southeast of Lambda (λ)
Aquarii and crosses into south-
ern Pisces June 25, south of the
Great Square of Pegasus. A
waning Last Quarter Moon lies
near Mars June 12/13.
Mars begins June at 9" in
apparent diameter, and grows to
11" by June 19. Telescopes reveal
a distinctive gibbous disk 84
percent lit. Visually, its features
remain a challenge, requiring
8- to 10-inch scopes under good
conditions. Video-frame capture
opens Mars observing to smaller
instruments, as does boosting
the magnification with a Barlow
lens. In the hour before dawn
during June’s first two weeks,
you may spot the Tharsis ridge
volcano region and the Mariner
Valley. By late June, the distinc-
tive dark Syrtis Major is evident.
Neptune is also in Aquarius
and stands 1.8° due north of
Mars on June 12. Observers can
easily swing to Neptune with a
scope and spy its 2.3" bluish
disk, which lies 30 times farther
than Mars (which is at 0.9
astronomical unit from Earth,
or nearly 84 million miles).
The outer planet lingers
while Mars drifts past over a
few days. At magnitude 7.9,
Neptune can be picked out
SKY THIS MONTH — Continued from page 37
By mid-June, comet C/2017 T2 passes out of the Big Dipper’s bowl to flirt
with some stunning deep-sky objects: M109, M106, and NGC 4449. Take
your time and compare the comet’s shape to those of these much more
distant wonders as it slides past.