10°January 4, 4 A.M.
Looking east-northeastDRACOURSA MINOR URSA MAJORBOÖTESCORONA
BOREALISHERCULESRadiantVegaArcturusQuadrantid meteor showerWWW.ASTRONOMY.COM 37— Continued on page 424th-magnitude Lambda (λ)
Aquarii. On the 1st, the planet
lies 0.5° southeast of Lambda.
By the 31st, Neptune stands
1.1° due east of the star. While
binoculars reveal the world as
a dim pinpoint, a telescope
shows the planet’s blue-gray
disk, which spans 2.2".
Uranus shines brighter
and lies farther east, against
the backdrop of eastern
Pisces. Although the planet
is an easy binocular object at
magnitude 5.8, Pisces has few
bright stars to guide you. Your
best bet is to home in on 5th-
magnitude Mu (μ) Piscium.
Uranus remains nearly sta-
tionary during January some
3° north of the star. And no
other object in the area shines
so brightly.
Uranus stands nearly 60°
above the southern horizon as
darkness falls. That’s the best
time to target the distant
Theophilus, Cyrillus, and CatharinaRISINGMOON
If there’s a best face to the Moon,
the thick waxing crescent phase
has to be it. Large waves seem to
swell across smooth seas, big cra-
ters take your breath away, and
small impacts stand out by casting
long shadows. On the evening of
January 22, the Serpentine Ridge
grabs your attention as a couplet of
light and darkness snaking across
Mare Serenitatis (Sea of Serenity)
north of the equator. Although it
looks like a frozen wave rippling
through the lava, it’s actually a
compression feature formed when
the mare lavas contracted.
Scanning southward, you’ll
cross Mare Tranquillitatis (Sea of
Tranquility) before running into
the crater Theophilus. This
60-mile-wide, sharp-edged impact
feature presents a complex jumble
of central peaks and slumped ter-
races on the rim’s inside slopes.
Just to its south lies Cyrillus.
Although this crater is the samesize as Theophilus, its softer edges
imply an older age.
Still farther south rests ancient
Catharina. Its lower, rounded rim
signifies a longer history of pum-
meling. The impact that created
Theophilus spread a rugged
debris apron north into the Sea
of Tranquility. Selenographers
named this bleak landscape Sinus
Asperitatis (Bay of Roughness).
The unusual double crater
Torricelli lies in this bay. Planetary
scientists think its weird shape
arose from a single glancing blow
instead of two unrelated events.
A fraction of a second after the
initial impact, what was left of the
projectile blasted through the
back wall of the developing main
crater. Torricelli — named after
the Italian scientist who invented
the mercury barometer — sits
off-center in a low-profile, bat-
tered bowl filled to the brim with
solidified lava.Reading ages from a crater’s structure
This trio of lunar craters on the waxing crescent Moon tells a tale
of advancing age, from Theophilus in the north to Catharina in
the south. CO NSO LI DATED LU NAR ATL A S/UA/LPL; INSET: NASA/GSFC/ASUNETorricelliSinus AsperitatisCyrillusTheophilusMETEORWATCH
Although the Quadrantids rank
among the year’s strongest show-
ers, the 2018 edition likely won’t
be memorable because of the
January 1 Super Moon. At the peak
before dawn on the 4th, bright
moonlight will wash out faint
meteors and make the brighter
ones less impressive. The hourly
rate can top 100 meteors in good
years, but observers may be lucky
to see 20 this year.
Observers shouldn’t give up,
however. Bright meteors still show
up through moonlight, and the
nice planet grouping before dawn
makes an early morning observing
session all the more worthwhile.The Super Moon’s
unwelcome impact
Quadrantid meteors
Active Dates: Dec. 28–Jan. 12
Peak: January 3/4
Moon at peak: Full Moon
Maximum rate at peak:
110 meteors/hourCatharinaThe Full Moon on January 31 slides deep into Earth’s shadow,
bringing a total eclipse to observers from North America to Asia.OBSERVING
HIGHLIGHTBright moonlight mars the peak
of January’s best meteor shower,
rendering it less impressive than
in most years.