AQUARIUSqNeptuneMercuryVenusrs s
sNE1°1°BOÖTESArcturuspdoPath of PallasApril 1611162126May 1NEPallas slides north through Boötes
Venus points the way to Neptune
GET DAILY UPDATES ON YOUR NIGHT SKY AT http://www.Astronomy.com/skythisweek.WWW.ASTRONOMY.COM 43Like spotting a lone sheep in a
grassy field, it should be easy to
find the 8th-magnitude asteroid
2 Pallas this month. It scoots
within 5° of the sky’s fourth-
brightest star, magnitude 0.0
Arcturus, the luminary of Boötes
the Herdsman. Although this
area remains visible all night, it
climbs highest soon after mid-
night local daylight time.
We even get a prominent
stepping-stone with magnitude
2.7 Eta (η) Boötis. On the eve-
ning of April 10, one night after
it reaches opposition, Pallas
slides just 2' east of Eta. You
should be able to detect its
motion in as little as 30 minutes.
Another good chance to see
Pallas shift positions comeswhen it approaches a wide pair
of 9th-magnitude stars April 29.
On other nights, use the
chart below to figure out where
Pallas will be and then swing
your scope to that spot. The
field will be otherwise empty
from April 3–8 and 14–23.
Because Pallas currently lies far
from the Moon’s path, Luna’s
light won’t interfere with your
asteroid hunting this month.
When Heinrich Olbers dis-
covered Pallas in March 1802,
it was just the second asteroid
known. (Giuseppe Piazzi spot-
ted the first, Ceres, in January
1801.) Astronomers initially des-
ignated both objects planets,
netting both discoverers con-
siderable fame.LOCATINGASTEROIDS
Strolling with the celestial Herdsman
competition comes when a
waning gibbous Moon appears
less than 3° west of the planet
April 25.
Any telescope reveals Saturn
as the showpiece of the solar
system. Its spectacular rings
span 38" and tilt 24° to our line
of sight in mid-April. They sur-
round a yellowish globe that
measures 17" across. As with
Jupiter, sharper views come as
it climbs higher before dawn.
Saturn’s brightest moons
are always on display. Because
they orbit near the gas giant’s
equatorial plane, which coin-
cides with the plane of the
rings, they all pass well north
or south of the planet’s disk.
Titan shines at 8th magnitude
and shows up through any
telescope. You can find it 1.1'
south of Saturn on April 2
and 18, and the same distance
north of the planet April 10
and 26.
A trio of 10th-magnitude
moons — Tethys, Dione, and
Rhea — circle Saturn inside
Titan’s orbit. You’ll need a
4-inch scope to pick them out.
A similar instrument should
bring in distant Iapetus. This
enigmatic moon, with one
hemisphere as bright as snow
and the other as dark as coal,
stands 1.1' south of Saturn on
April 7. It then glows at 11th
magnitude because we see
roughly equal parts of each
hemisphere. As the moon
moves west of Saturn after-
ward, its brighter side rotates
into view. It brightens to 10th
magnitude by the time it
reaches greatest elongation
April 28, but it then lies 9'
from the planet and will be
harder to identify.
Twilight begins before the
next bright planet appears.
Venus rises in the east
around 5:30 a.m. local day-
light time April 1 and a half-
hour earlier by month’s end.
Unfortunately, the Sun also
comes up earlier in late April,
and Venus then appears
deeper in twilight. Still, the
inner planet shines brilliantly
at magnitude –3.9 and stands
out in the brightening sky.
You can use Venus to
track down Neptune on
April 10. The two then appear
0.3° apart and lie in the same
field of view through a tele-
scope at low power. You’ll
need an exceptionally clear
sky to spot 8th-magnitude
Neptune, however, because
it’s low and in twilight. From
mid-northern latitudes, the
pair stands 7° high a half-
hour before sunrise.
Conditions improve mark-
edly the farther south you
live; from mid-southern lati-
tudes, the planets stand15° high as twilight begins.
Don’t confuse Neptune with
the 4th-magnitude star Phi (φ)
Aquarii, which lies 5' south
of the outer planet.
Sharp-eyed observers also
should see Mercury through
binoculars. The innermost
planet shines at magnitude 0.3
5° east of the Venus-Neptune
pair. Mercury reaches greatest
elongation April 11, when itlies 28° west of the Sun but
climbs only 4° high a half-
hour before sunrise. Once
again, Southern Hemisphere
viewers have better views.Martin Ratcliffe provides
planetarium development for
Sky-Skan, Inc., from his home in
Wichita, Kansas. Alister Ling,
who lives in Edmonton, Alberta,
has watched the skies since 1975.The brightest planet guides you to the dimmest one shortly before dawn
April 10. The two worlds appear higher in a darker sky from farther south.
The second asteroid discovered reaches opposition April 9, though
the 8th-magnitude object remains a tempting target all month.