10°SAGITTARIUS
CEPHEUS
PEGASUS
CYGNUS
AQUILA
LYRA
HERCULES
CAPRICORNUS
OPHIUCHUS
VegaDenebAltairJupiter
SaturnRadiantApril 22, 4:30 A.M.
Looking eastWWW.ASTRONOMY.COM 33
RISING MOON I A heartfelt sunrise
THE SEA OF SERENITY’S dark floor is strewn
with pits, bumps and ridges when the Moon
appears sliced in half. On the 17th, the snaking
Serpentine Ridge captures our attention with
its long play of light and dark across this huge
impact basin just north of the lunar equator.
By the following night, the Sun has risen
over the western half of Serenity’s ancient
lava-filled bowl, bringing to light some compar-
atively young craters. Strung out in a line from
north to south are Linné G, H, F, B and A, with
F and B the biggest at 3 miles (1.6 kilometers)
across.
The Valentine Dome is a gentle volcanic pro-
trusion tucked against the western flank of
Serenity, visible only at the lowest of Sun angles.
Timed perfectly for the 18th, its somewhat heart-
shaped swelling crests less than 400 feet
(122 meters) above the floor. You won’t be able
to miss the handful of older peaks sticking above
the dome. One Earth night later (the 19th),
the shade of the gentle slopes has dis-
appeared under the higher Sun, leav-
ing but a trace of the tiny tops.
The low angle returns at lunar
sunset, when the Sun is shining
from the Moon’s west. This aptly
named “reversed light” occurs about
two weeks earlier on April 3, and again
on May 2.improves next month as they
glide past the Pleiades star clus-
ter (M45).
Mars lies high in the west-
ern sky after sunset, joining
the stars of Taurus the Bull.
It shines at magnitude 1.3
on April 1 and fades to 1.6
by the end of the month.
Compare the Red Planet’s sig-
nature orange-colored glow
to Aldebaran, the Bull’s
magnitude 0.9 star. Aldebaran,
a glowing star emitting its own
light, appears reddish due to its
“cool” surface temperature
around 6,700 degrees
Fahrenheit. But Mars is a cold,
rocky planet and has no light
of its own. Instead, its ruddy
color occurs because it ref lects
sunlight preferentially in the
red part of the spectrum, due
to the makeup of its rusty sur-
face material.
Mars tracks slowly through
Taurus. Between April 12 and
13, it passes between the two
stars marking the horns of the
Bull — Alheka (Zeta [ζ] Tauri)
and Elnath (Beta [β] Tauri).
The planet crosses into Gemini
April 24, then early on the 27th
passes delightfully 0.5° north
of M35, a fine open cluster in
Gemini with a few colored
stars. Grab a pair of bin-
oculars to soak in this
stunning sight, as well as
pick up an additional tar-
get: Located just 0.5°
southwest of M35 is an
The Valentine Dome
— Continued on page 38
METEOR WATCH I A springtime show
THE SPRINGTIME LYRID meteor
shower is like a welcome friend
returning with the warmer weather.
This annual shower is active from
April 14 to 30 and peaks the morn-
ing of April 22. The radiant, located
in the compact constellation Lyra
the Harp, rises in the late evening
and stands about 20° high at local
midnight. A 10-day-old Moon will
affect observations until it sets
around 4 A.M. local time, offering an
hour of dark skies before twilight
begins. This early morning hour is
the best time to view the shower,
which can generate an average of
up to 18 meteors per hour when
the radiant is overhead. Most
meteors are best seen from dark
sites, well away from streetlights,
and with dark-adapted eyes, which
allow fainter members of the
shower to be observed.Lyrid meteor shower
The heart-shaped Valentine Dome is a bit
tricky to spot, but well worth the effort.
CO NSO LI DATED LU NAR ATL A S/UA/LPL. INSET: NASA/GSFC/ASUThe Lyrids’ radiant will reach 80° altitude
around 4:30 A.M., slightly attenuating the
shower’s maximum rate.LY R ID ME TEORS
Active dates: April 14–30
Peak: April 22
Moon at peak: Waxing gibbous
Maximum rate at peak:
18 meteors/hourLinnéNEMARS is the only planet visible
most of the night. On April 25, it
passes 0.5° north of M35, with
NGC 2158 also visible nearby.OBSERVING
HIGHLIGHT
Valentine DomeGHFAB