10°SCORPIUSAQUILAAQUARIUS
CAPRICORNUSSAGITTARIUSSaturnMarsAltairLate July, 10 P.M.
Looking southeastMars at its peak (^)
36 ASTRONOMY • JULY 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.
July 2018: The Red Planet’s revival
SKYTHIS
MONTH
J
uly features the finest
views of Mars in 15 years.
But that’s just one high-
light in a month full of
them. The five planets
known since antiquity span
the evening sky: Mercury
and Venus appear in twilight,
Jupiter and Saturn remain vis-
ible until after midnight, and
Mars is a showpiece all night.
As if to underscore the Red
Planet’s peak, a total eclipse of
the Moon visible from most of
the Eastern Hemisphere occurs
near Mars on the night of July
27/28. Binoculars will show
Uranus and Neptune as they
climb high before dawn, and a
telescope reveals Pluto sliding
past a bright star. It’s a great
month to watch the night sky,
so let’s get started.
Evening twilight hosts both
Mercury and Venus. Mercury
planet from the Sun shines at
magnitude –4.1 in early July
and brightens to magnitude
–4.3 by month’s end. Venus
spends July among the back-
ground stars of Leo, passing
1° north of 1st-magnitude
Regulus on the 9th.
A waxing crescent Moon
slides 2° to the planet’s right
July 15. The stunning duo
stands 15° high in the west
45 minutes after sundown. The
conjunction provides a nice
photo opportunity. Shoot the
twilight scene before 9:30 p.m.
local daylight time and you’ll
also capture Regulus to the
lower right and Mercury closer
to the horizon. Point a tele-
scope at Venus this evening
and you’ll see an 18"-diameter
disk that appears nearly two-
thirds illuminated.
As Venus and the Moon slip
close to the horizon, shift your
gaze to their left and you’ll
encounter Jupiter, Saturn, and
then Mars. Jupiter appears
about 30° high in the south-
west while Saturn stands 20°
crosses from Cancer into Leo
this month, passing within 1°
of the Beehive star cluster
(M44) July 3 and 4. The
innermost planet glows at
magnitude 0.0 and should be
easy to spot with your naked
eye, though you’ll need bin-
oculars and a transparent sky
to see M44. The two stand 7°
high 45 minutes after sunset.
Mercury dims and dips
closer to the horizon as July
progresses. It crosses into Leo
on the 14th, when a slender
crescent Moon passes 2° above
it. Use binoculars to best view
the pair. A telescope reveals
Mercury’s 8"-diameter disk,
which appears 38 percent lit.
Evening twilight swallows the
planet within another week.
As you search for Mercury,
you can’t help but see Venus
to its upper left. The second
high in the south-southeast.
And Mars pokes above the
southeastern horizon around
9:30 p.m. local daylight time.
The solar system’s two gas
giants are on view every clear
evening. Jupiter lies in Libra,
2° northwest of Zubenelgenubi
(Alpha [α] Librae). Saturn
resides in northern Sagittarius,
not far from several deep-sky
gems. Jupiter shines at magni-
tude –2.2 in mid-July, nearly
10 times brighter than magni-
tude 0.1 Saturn. Both remain
within 0.1 magnitude of these
values all month.
Catch Jupiter first while it
is still high in the sky. The
giant planet’s equator spans
41" in early July and 38" late in
the month. Despite its dwin-
dling size, Jupiter remains a
fine object through telescopes
of all sizes. Any instrument
shows its two dark equatorial
belts, one on either side of a
noticeably brighter zone.
Jupiter’s dynamic atmo-
sphere can provide hours of
enjoyment, but it’s also worth
Mars puts on its best show in 15 years this month. The Red Planet spans
24.3" in late July, when telescopes should show an impressive array of
surface features. NASA/ESA/THE HUBBLE HERITAGE TEAM (STSCI/AURA)/J. BELL (ASU)/M. WOLFF (SSI)
The Red Planet shines at magnitude –2.8 when it reaches opposition in late
July among the dim stars of Capricornus. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY