Late June, 10 P.M.
Looking southeastSAGITTARIUSOPHIUCHUSAQUILASCORPIUSAntaresSaturn10°Saturn at its peak (^)
36 ASTRONOMY • JUNE 2018
Visible to the naked eye
Visible with binoculars
Visible with a telescope
MARTIN RATCLIFFE and ALISTER LING describe the
solar system’s changing landscape as it appears in Earth’s sky.
June 2018: Saturn takes center stage
SKYTHIS
MONTH
O
ur great run of spring
and summer planets
continues this month
as Saturn comes to
opposition and peak
visibility. Meanwhile Jupiter, a
month past its own opposition,
lights up the sky from evening
twilight until the wee hours.
And Mars, which will reach
opposition in July, stands out
from late evening until dawn.
sunset. Mercury lies 7° high
and should be fairly easy to
spot in the twilight with your
naked eyes, because it shines
brightly at magnitude –0.8.
That same evening, the planet
forms a skinny triangle with
Gemini’s twins, Castor and
Pollux. These bright stars stand
side by side 10° above Mercury.
As the month progresses,
Mercury’s visibility improves as
it climbs away from the Sun. Its
ascent coincides with Gemini’s
descent, and on June 27, the
planet sits in line with Castor
and Pollux. Mercury (now at
magnitude –0.3) appears on
the left with Pollux 7° to its
right and Castor 4.5° beyond it.
The trio stands 10° high a half-
hour after sundown.
Mercury typically appears
as a blurry disk through a tele-
scope because its light has to
pass through a lot of Earth’s
turbulent atmosphere. On
June 19, the planet spans 5.6"
and shows an 81-percent-lit
phase. By the 27th, it appears
6.3" across and 66 percent
illuminated.
But the planetary delights
begin with splendid appear-
ances by the two inner planets
shortly after sunset. We’ll
start our tour with innermost
Mercury as it climbs into
view after midmonth.
Your first good chance to
spot this world comes June 19.
Scan the area above your
west-northwestern horizon
starting 30 minutes after
As you gaze at Mercury,
you no doubt will notice a
much brighter object higher
in the west. Venus brightens
from magnitude –3.9 to –4.1
during June and is by far the
brightest point of light in the
sky. As the month opens, the
dazzling object lies in central
Gemini 9° below Pollux. By
June 11, it stands 6° to the left
of this 1st-magnitude star.
Although it appears near
Gemini’s brightest star on the
11th, it actually crosses into
neighboring Cancer that same
day. A waxing crescent Moon
joins it June 15 and 16. On the
15th, Luna hangs 7° below the
planet; on the 16th, our satel-
lite climbs 8° to Venus’ upper
left. On this latter evening,
the superb Beehive star clus-
ter (M44) stands midway
between the planet and the
Moon. Once the sky grows
dark, grab your binoculars
for some amazing views of
Venus, the cluster, and the
Moon bathed in earthshine.
Venus skirts the northern
edge of M44 on the 19th, pass-
ing just 44' from the cluster’s
center. This presents a golden
photo opportunity. The stun-
ning jewels of the Beehive are
a favorite target for astroimag-
ers, and Venus’ brilliant light
adds a nice touch.
The planet continues east-
ward through the rest of June,
crossing into Leo on the 29th
and ending the month 10° shy
of the Lion’s brightest star,
1st-magnitude Regulus.
Surprisingly, Venus hangs a
bit lower in the evening sky as
June wraps up. It stood 16°
high an hour after sunset in
early June, but its altitude
drops to 15° by month’s end.
And by the time it reaches
With Saturn looming large and the rings wide open, this month promises exquisite views of the planet’s ring
structure, including the broad Cassini Division and thin Encke Gap. NASA/ESA/THE HUBBLE HERITAGE TEAM (STSCI/AURA)
The ringed planet shines brightest in late June, when it remains visible all
night against the backdrop of Sagittarius. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY