Looking westMay 17, 1 hour after sunsetVenus
MoonBetelgeuseCapellaProcyonPollux CastorORIONTAURUSAURIGAGEMINI10°NE1°Path of Ceres31262116116May 1oigh¡CANCERLEOCatch a bright dwarf planetThe Moon passes Venus (^)
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If you’ve never seen a dwarf
planet before, May offers a
perfect opportunity. Ceres, the
largest object in the asteroid
belt between Mars and Jupiter,
slides past magnitude 4.5
Kappa (κ) Leonis on the evening
of the 18th. Point your tele-
scope at Kappa and then look
for a magnitude 6.8 star half
the Full Moon’s diameter to the
south-southwest. Magnitude 8.5
Ceres lies between the two and
slightly closer to Kappa. You
can see the dwarf planet move
in under an hour as a nearly
straight line becomes crooked.
If it’s cloudy on the 18th,
don’t despair — Ceres soon
crosses a field conducive to star-
hopping, with plenty of unusual
patterns containing unequal
stars. Those are easy to sketch
quickly, providing a framework
that makes Ceres’ night-to-night
movement noticeable. You can
see it shift positions in a single
evening again on the 24th,
when it passes a crooked line
of three fainter stars.
Viewing Ceres in the first half
of May won’t be as easy. Still, a
3-inch scope under suburban
skies will pull it in. Your best bet
is to start at Kappa and hop over
the border into Cancer. Just be
patient so as not to get lost in
the abundance of field stars.
LOCATINGASTEROIDS
Passing through the Lion’s den
Mars rises shortly before
1:30 a.m. local daylight time as
May opens. It then lies in east-
ern Sagittarius, 15° east of
Saturn. Unlike Saturn, how-
ever, the Red Planet moves
eastward quickly. It passes 0.3°
south of the 9th-magnitude
globular cluster M75 on the
14th; by the next morning, it
has crossed into Capricornus.
It will remain in the Sea Goat
until late August. The planet’s
eastward journey partially
compensates for the Sun’s own
easterly motion, and Mars still
rises after midnight in late May.
Your best views through a
telescope come shortly before
twilight begins. By then, Mars
has climbed about 25° high in
the south-southeast. (It
appears higher the farther
south you live.) The planet’s
visible hemisphere changes
little from one night to the
next because Mars rotates just
a bit slower than Earth. If you
observe the Red Planet at the
same time each morning, the
longitude at the center of the
disk shifts only 9.1° each day.
For observers in North
America on May’s first few
mornings, the dark, wedge-
shaped feature known as Syrtis
Major stands at the center of
the martian disk. A week later,
the dark, fingerlike Mare
Cimmerium takes center stage.
The volcanic Tharsis region
rotates into view on mornings
in mid-May. And by the 21st
and 22nd, Solis Lacus appears
quite prominent.
The remaining planets
cluster low in the east before
sunrise. Neptune rises at the
break of dawn in early May
but becomes a much easier
target late in the month. On
the 31st, it rises around 2 a.m.
local daylight time and climbs
20° high in the east-southeast
as twilight commences.
Glowing at magnitude 7.9,
it’s an easy binocular object
set against the backdrop of
Aquarius. Look for it 1.0°
west of 4th-magnitude
Phi (φ) Aquarii.
Uranus pops into view at
the end of May. After a five-
year stint among the back-
ground stars of Pisces, the
distant planet now resides in
Aries. You can find it through
binoculars 10° due south of
3rd-magnitude Beta (β)
Arietis and 3° northeast of
4th-magnitude Omicron (ο)
Piscium. Uranus shines at
magnitude 5.9 and shows
up quite easily through
binoculars.
Our final planet never
escapes morning twilight
this month for observers at
mid-northern latitudes.
Mercury reached greatest
western elongation April 29,
and it remains low in the east
before dawn in early May.
On the 1st, it stands 4° high
30 minutes before sunrise. It
then shines at magnitude 0.3
and should be visible through
binoculars if you have an
unobstructed eastern horizon.
If you’re ambitious, you can
follow Mercury for another
week or two. Although the
innermost planet slowly loses
altitude, it also brightens. On
the 15th, it appears 3° high a
half-hour before sunup and
shines at magnitude –0.3.
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.
A waxing crescent Moon teams up with brilliant Venus to form a stunning
pair in the western sky after the Sun sets May 17.
Although Ceres fades from magnitude 8.4 to 8.7 this month, it should be
easy to find as it crosses from Cancer into Leo.