SAGITTARIUS13July 1
3
5
7
9
11Path of Pluto0.025°EN500.5°OPHIUCHUS^31July 1
6
11
16
21
26Path of Vesta51525844jNEVesta comes to the fore (^)
Pluto makes a close pass
GET DAILY UPDATES ON YOUR NIGHT SKY AT http://www.Astronomy.com/skythisweek.
WWW.ASTRONOMY.COM 43
The second-largest object in
the asteroid belt, 4 Vesta, is the
brightest. Not only does Vesta
orbit closer to the Sun (and thus
Earth) than dwarf planet Ceres,
but its surface reflects more
sunlight. Vesta should be easy
for beginners to track through
binoculars from the suburbs,
and a challenge for seasoned
observers to follow with their
naked eyes from a dark site.
Vesta fades from magni-
tude 5.6 to magnitude 6.3 this
month as it crosses one of the
legs of Ophiuchus the Serpent-
bearer. With binoculars, start at
magnitude 2.4 Eta (η) Ophiuchi
and then drop south one field
to magnitude 4.4 Xi (ξ) Oph.
Our target lies a little to the left
(east) of Xi. Before you head
out, make a sketch of the
brighter anchor stars using the
chart below. Once you’re under
the stars, add the ones near
Vesta’s position. Return a cou-
ple of nights later to see which
one has moved.
Experienced skywatchers
are familiar with the Prancing
Horse dark nebula just west of
our galaxy’s nucleus. During
the New Moon weekend of
July 14, Vesta crosses the dusky
steed’s front shoulder. The
contrast between asteroid
and cloud should help veteran
observers spot Vesta without
optical aid.
LOCATINGASTEROIDS
Spotting the easiest asteroid of all
around 10 p.m.). The ruddy
world then rises around sunset
and peaks in the south shortly
before 1 a.m.
When viewing detail on
Mars’ surface through a tele-
scope, it all comes down to
angular size. It’s a small planet
to begin with, so the weeks
surrounding opposition are
special. Mars spans 20.9" on
July 1 and grows to 24.3" by
month’s end.
A day on Mars lasts 37 min-
utes longer than on Earth. This
means if you observe at the
same time each night, mark-
ings appear to shift westward
9.1° per day, so you can view
the entire planet during the
course of the month. Features
appear best when they lie near
the central meridian — the line
joining Mars’ north and south
poles that passes through the
disk’s center — though they
remain visible for a couple of
hours on either side.
Both Syrtis Major, a promi-
nent dark feature with a trian-
gular shape, and the bright
Hellas Basin cross the central
meridian around 2 a.m. EDT
on July 12 and 13. Don’t con-
fuse Hellas with the brighter
south polar cap on the planet’s
limb. The bright Elysium plain
takes center stage at 2 a.m.
EDT on July 21. At the same
time on the night of opposition,
Mare Sirenum appears on the
central meridian.
Less than 24 hours after
Mars reaches opposition, the
Full Moon plunges through
Earth’s shadow. Observers
across most of Europe, Asia,
Africa, and Australia will see
a total lunar eclipse, with the
eclipsed Moon hanging 7°
north of Mars. Totality runs
from 19h30m to 21h13m UT
on July 27 (before dawn on
the 28th for people in eastern
Asia and Australia). The
103 minutes of totality makes
this the longest total lunar
eclipse since 2000.
After the thrilling sight of
Mars, July’s final two planets
might be a letdown. But
Neptune and Uranus deserve
a few moments of your time.
Neptune lurks in eastern
Aquarius, rising around mid-
night on the 1st and two hours
earlier by month’s end. The
distant world glows at magni-
tude 7.8, so you’ll need bin-
oculars or a telescope to spot
it. Wait until it climbs high in
the south before dawn and
then zero in on 4th-magnitude
Phi (φ) Aquarii. Neptune lies
west-southwest of Phi all
month; it is 0.9° from the star
on the 1st and 1.4° away on
the 31st. A telescope reveals
the planet’s blue-gray disk,
which measures 2.3" across.
Plan to target Uranus
shortly before twilight begins.
The magnitude 5.8 planet then
lies reasonably high in the east
and should be easy to find
through binoculars. It lies in
southwestern Aries some 12°
south of 2nd-magnitude Alpha
Arietis. A few 6th-magnitude
stars lie in the planet’s vicinity,
so you’ll need a telescope to
confirm a Uranus sighting.
Only the planet shows a dis-
tinct blue-green color and a
3.5"-diameter disk.
Martin Ratcliffe provides plane-
tarium development for Sky-Skan,
Inc., from his home in Wichita,
Kansas. Meteorologist Alister
Ling works for Environment
Canada in Edmonton, Alberta.
Spying this 14th-magnitude dwarf planet is a bit easier than normal when
it skims just north of 6th-magnitude 50 Sagittarii during July’s first week.
The sky’s brightest asteroid should be an easy target as it wanders
southwest against the backdrop of Ophiuchus the Serpent-bearer.