Spy the zodiacal lightThe ghostly ring of LamontWWW.ASTRONOMY.COM 37METEORWATCH
The annual calendar of meteor
showers suffers a lull between
early January’s Quadrantids and
the Lyrids of late April. Observers
under a dark sky typically can see
a half dozen or so meteors per
hour shortly before morning twi-
light begins.
But the tiny dust particles that
cause these sporadic meteors also
permeate the inner solar system.
These fine grains show up as a
cone-shaped glow in the west on
dark February evenings. Because
the dust hugs the solar system’s
plane, or ecliptic, the glow aligns
with the zodiacal constellations and
astronomers call it the “zodiacal
light.” It appears best on evenings
in February and March because
the ecliptic then makes a steep
angle to the western horizon.Catch the zodiac’s
mysterious glow
— Continued on page 42Saturn line up along the eclip-
tic — the Sun’s apparent path
across our sky that the planets
follow closely. They form a
beautiful wintery scene once
Saturn, the last to rise, clears
the horizon by 5 a.m. local
time. But the most stunning
vistas come when the trio
becomes a quartet as a wan-
ing Moon slides past from
February 7 to 11.
Jupiter is the first to rise.
It pokes above the horizon
shortly before 2 a.m. local
time in early February and
nearly two hours earlier by
month’s close. It lies in Libra,
a constellation that climbs 30°
high by 5 a.m. The brilliant
orb dominates the predawn
sky throughout February,
brightening from magnitude
–2.0 to –2.2 during the month.
The Last Quarter Moon
passes 4° to Jupiter’s upper
right on the 7th.
The giant planet’s disk
spans 37" in mid-February and
offers an observational treat to
anyone who targets it through
RISINGMOON
The waxing crescent Moon not
only thrills neophyte viewers,
but it also delights veteran sele-
nophiles. Late winter and early
spring are the best times to view
this lunar phase because the
ecliptic — the apparent path of
the Sun across our sky that the
Moon and planets follow closely
— makes a steep angle to the
western horizon after sunset.
Thus, the waxing crescent Moon
appears higher in the sky than it
does at other times of year.
Let’s focus on Luna the eve-
ning of February 20, less than
three nights before First Quarter
phase. The 25-percent-lit Moon
stands more than 40° high in the
southwest an hour after sunset
and remains on view well past10 P.M. local time. Aim your tele-
scope toward Earth’s satellite
and focus your attention just
north of the equator. On the
western shore of Mare
Tranquillitatis (Sea of
Tranquility), you’ll find a zone
rife with sinewy ridges adorning
the mare’s frozen face.
Literally buried under
Tranquility’s mostly north-south
ridges is a ghostly ring named
Lamont. Astronomers think this
was a fairly normal impact crater
in the Moon’s youth. But lava
welling up from beneath the
surface flooded the crater to its
rim a few billion years ago, leav-
ing behind the ghostly ring. A
second ring, about twice
Lamont’s size and concentricImpacts that disturb a tranquil sea
Mare Tranquillitatis’ western shore harbors sharp-rimmed Arago just
northwest of ghostly Lamont. CO NSO LI DATED LU NAR ATL A S/UA/LPL; INSET: NASA/GSFC/ASUNEAragowith it, is trickier to see under
less-than-ideal conditions.
Long after Lamont formed, a
smaller impactor carved out the
16-mile-wide crater Arago to its
northwest. Look just north of
Arago and you’ll see a modestbump, which is the largest of
a family of volcanic domes in
this neighborhood. The rings
and domes have such gentle
slopes that they disappear
under the higher Sun angle
the following evening.Mare TranquillitatisLamontThe soft, pyramid-shaped glow of the zodiacal light stands above the
western horizon after darkness falls during February’s first half. JEFF DAIA partial solar eclipse occurs over southern South America and
parts of Antarctica on February 15.OBSERVING
HIGHLIGHTLook for this soft glow under a
dark sky from February 2 to 16,when the Moon is out of the
early evening sky.