10°Jan. 3, 4 A.M.
Looking northeastRadiantCORONA
BOREALISBOÖTESDRACOCYGNUSHERCULESDenebVegaLY R ARasalgethiAlpheccaWWW.ASTRONOMY.COM 33RISING MOON I Ports in a storm
THERE’S NO HIDING the crater
Kepler! The youthful impact scar
stands out on the Moon’s equator,
a veritable island in Oceanus
Procellarum, the large basin on
the eastern flank of our satellite.
Kepler is a smaller version of the
prominent Copernicus, which lies
closer to the Moon’s center.
Kepler is a round, sharply
defined deep bowl. On the 13th,
the low Sun angle highlights the
rough skirt of debris that spread
out during the impact event that
created it. A bit to the
south lies Encke, simi-
lar in size to Kepler,
but its older, bom-
barded rims are
softer and, more
importantly, it is
filled with Kepler’s
rubble.
Return in the next couple of
evenings to see how a higher Sun
angle transforms the roughnessreaches greatest elongation east
(19° from the Sun) Jan. 7, then
shining at magnitude –0.5.
Saturn and Mercury appear
closest on the evenings of
Jan. 12 and 13, separated by
3.4°. Mercury has dipped in
brightness to magnitude 0.4 by
the 14th, and matches Saturn’s
brilliance the next evening. The
smaller planet fades further as
it begins a brisk inward path to
its Jan. 23 inferior conjunction.
By Jan. 17, it has dimmed to
magnitude 1.7 and become
much harder to spot in bright
twilight. Mercury sets within
an hour of sunset.
Saturn falls in altitude each
evening as well. On Jan. 4,
catch the Moon and Saturn
side by side, separated by about
5°. Saturn becomes lost in the
solar glow a few days after
Mercury and is no longer easily
observable. It’s only 5° high 30
minutes after sunset on Jan. 20
and, at magnitude 0.7, it’s easily
lost in twilight.
Jupiter maintains its visibil-
ity throughout the month. It’s a
fine object in late twilight in the
first week of January and is the
brightest of the evening planets
after Venus leaves the scene. On
Jan. 1, Jupiter stands roughly 30°
high in the southwest an hour
after sunset. On Jan. 5, Jupiter is
5° north of the crescent Moon,
now just over 3 days old.
Jupiter’s disk spans 35" and
easily shows off its dusky orange
Kepler and Encke
and shadows into a bright
apron with rays. The lava of
Procellarum is thinner here,
which permitted the impact to
gouge out lighter-hued rockfrom below. To the south,
Encke has all but disappeared.
Typically, the older the crater,
the less it is visible under a
high Sun.— Continued on page 38METEOR WATCH I A fine New Year’s show
THE QUADRANTIDS, which
originate in what is now the
northern region of Boötes, are
active between Dec. 28 and
Jan. 12. The narrow peak ofactivity (six hours, according
to the International Meteor
Organization) occurs Jan. 3.
With the Moon near New, if
the weather cooperates, theQuadrantid meteor shower
chances are good for a fine view. The
predawn hours are always the best
time to view meteor showers, and
the Quadrantids are no exception.
The radiant rises late in the evening
and by 4 A.M. local time, it’s about 40°
high. Expect about 25 to 30 meteors
per hour if the peak occurs during
the dark window of your observing
site, corresponding to a zenithal
hourly rate of 100 to 120. Look also
for the occasional fireball known to
occur with this shower.
The Quadrantids’ parent object,
2003 EH 1 , was discovered in 2003 by
Brian Skiff at Lowell Observatory.
The former comet nucleus now car-
ries a typical asteroid designation
and its orbital parameters closely
match those of Quadrantid meteors.The impact craters Copernicus, Kepler, and Encke are easy to
find on Luna’s face. CO NSO LI DATED LU NAR ATL A S/UA/LPL. INSET: NASA/GSFC/ASUThe Quadrantids’ radiant is highest before dawn in January. It lies in
the now-defunct constellation Quadrans Muralis.QUADRANTID METEORS
Active dates: Dec. 28–Jan. 12
Peak: Jan. 3
Moon at peak: Waxing crescent
Maximum rate at peak:
120 meteors/hourCopernicusNEMERCURY and SATURN mingle
close together the evenings
of Jan. 12 and 13, when the two
sit 3.4° apart.OBSERVING
HIGHLIGHT
KeplerEncke