SKY THIS MONTH
Visible to the naked eye
Visible with binoculars
Visible with a telescope36 ASTRONOMY • JUNE 2020
All seven major
planets are visible
during June’s short summer
nights. Mercury is a fine eve-
ning object, while Venus pops
up in the morning sky after its
inferior conjunction. The solar
system’s two dominant planets,
Jupiter and Saturn, stand
near each other in our skies
all summer. They are nearing
their peak and best seen in the
morning hours. Mars is grow-
ing in brilliance and apparent
size, gaining altitude in the
pre-dawn sky. The trend hints
at what should be a superb
apparition in late 2020. Both
Uranus and Neptune are within
reach of binoculars, completing
the rich planetary stage.
Mercury is well placed for
U.S. observers during the first
two weeks of June as it climbs to
its June 4 greatest eastern elon-
gation (24°), set against the
backdrop of Gemini the Twins.
In twilight, the twins’ brightest
stars, magnitude 1 Castor and
Pollux, stand out an hour after
sunset when you look west.
On June 1, Mercury shines
at magnitude 0.1 and fades to
1.4 by June 13, when it stands
11° below Pollux. On June 4,
Mercury sets nearly two hours
after the Sun, providing ample
opportunity to view the inner-
most planet. Try to spot the tiny
8"-wide disk in your telescope
— it’s challenging at the planet’slow altitude (7° one hour after
sunset for latitudes near 40°
north). The disk is 36 percent lit
and drops to a 19 percent illu-
minated crescent by June 13.
That narrowing crescent
increases in angular size, reach-
ing 10" on the same date.
Mercury fades and sets ear-
lier each evening, making itprogressively harder to spot in
mid-June. It dims to 2nd mag-
nitude and is just 3° high 45
minutes after sunset on June 16.
Jupiter and Saturn rise
within 17 minutes of each other,
around midnight on June 1.
They straddle the border of
Sagittarius the Archer and
Capricornus the Sea Goat. Both
are approaching a July opposi-
tion and move in a retrograde
(westerly) direction. Jupiter, by
virtue of its relative nearness
compared with Saturn, moves
farther west than its ringed
counterpart. A waning gibbous
Moon lies near the two planets
on June 8 and 9.
On June 1, Jupiter lies 4.8°
west of Saturn. By June 30, that
gap has increased to 6°. Jupiter
begins the month at magnitude
–2.6 and brightens to –2.7 by
June 30. Soak in the remarkable
view through 7x50 binoculars.
The scene captures not only the
solar system’s two largest plan-
ets, but also M75, a globular
cluster 68,000 light-years away
and orbiting our Milky Way
Galaxy. It’s a faint, fuzzy object
shining at magnitude 9.5 and
lying 1.5° south of the line join-
ing Jupiter and Saturn.
The best views of both plan-
ets occur in the hours before
dawn, when they stand about
30° high from a latitude of 40°
north. By the end of June, they’re
well above the horizon an hour
or two after local midnight.
Telescopic views reveal
Jupiter’s 45"-wide disk, which
grows to 46.6" by the end of the
month. If the atmosphere above
your observing site is steady,
you’ll be treated to spectacular
views of its belts and zones, and
occasionally the Great Red Spot.
All features rotate in under 10
hours, so changes in appearance
are noticeable over a 15-minute
period. Jupiter’s brilliance canSaturn
JupiterCORONA
AUSTRALISCAPRICORNUSSAGITTARIUSSCUTUMJune 15 , 1 hour before sunrise
Looking south-southwest10 °Giant planets dazzle before dawn (^)
The solar system’s largest planets, Jupiter and Saturn, stand roughly 5° apart
at midmonth. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY
THE SOLAR SYSTEM’S CHANGING LANDSCAPE AS IT APPEARS IN EARTH’S SKY.
BY MARTIN RATCLIFFE AND ALISTER LING
JUNE 2020
Jupiter
and Saturn
shine together
This shot from
Forsyth, Georgia,
captures the moment
just before the Moon
occulted Venus in
December 2015. On
June 19, observers in
the northwestern
half of Europe and
northern and eastern
Canada, as well as
parts of Maine and
Massachusetts, will
see a similar show.
STEPHEN RAHN