10°AQUILA OPHIUCHUSSCORPIUSSAGITTARIUSShaulaAltairVenusMid-February, 45 minutes before sunrise
Looking southeast0.5°ζTAURUSMarch 1Path of HerculinaFeb 15913172125NE M1^114Perched on the Bull’s southern hornVenus reaches greatest brilliancy (^)
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February’s first few mornings.
During February’s final week,
the conspicuous dark feature
Syrtis Major dominates the
planet’s central region. Also
look for Mars’ white north
polar cap. Although the cap
is now waning — summer
begins in the northern
hemisphere February 14 —
it should stand out because
the planet’s north pole tips in
our direction.
Saturn pokes above the
horizon roughly two hours
after Mars. The ringed planet
lies against the backdrop of
Libra the Balance. It shines
at magnitude 0.5, two full
magnitudes brighter than
any of Libra’s stars. Saturn’s
southerly position this year
means that it won’t climb high
for observers at mid-northern
latitudes. For the best views in
February, wait until an hour
or so before dawn. Even a
small telescope reveals the
planet’s 17"-diameter disk
encircled by a ring system that
spans 39" and tilts 23° to our
line of sight.
For amateur astronomers,
Saturn offers more moons to
view than Jupiter does. None
rises to the brightness of Jupi-
ter’s four largest, however.
Only 8th-magnitude Titan
shows up through the smallest
scopes. Simply look for the
brightest point of light near
the planet. You’ll find Titan
south of Saturn on February
2/3 and 18/19 and north of the
planet February 11 and 27.
Saturn’s outermost major
moon, two-faced Iapetus, var-
ies in brightness by a factor of
five as it orbits the planet. The
best time to look for it this
month comes February 16
when it passes 2.2' due north
of the ringed world. It then
glows at 11th magnitude and
should show up easily through
a 6-inch scope.
Three other moons appear
through 4-inch instruments.
Tethys, Dione, and Rhea glow
at 10th magnitude and all
orbit inside Titan. It is worth
the effort to view the trio
when they lie near one
another before dawn February
11 and 21. On the 11th, the
three form a 44"-long line
west of Saturn; on the 21st,
they make an even tighter
triangle east of the planet.
By the time twilight
begins, Venus dominates the
sky. The brilliant world rises
some two hours before the
Sun in early February, when it
shines at magnitude –4.8. The
morning “star” grows even
more prominent as the month
progresses and it climbs
higher before dawn. Venus
reaches greatest brilliancy
(magnitude –4.9) February 15
before fading back to magni-
tude –4.8 by month’s end,
when it comes up 2½ hours
before our star.
The view of Venus through
a telescope changes dramati-
cally during February. On the
1st, Earth’s neighbor spans 51"
and shows a thin crescent just
13 percent lit. By the 28th,
Venus’ apparent diameter has
shrunk to 33", but the Sun
then illuminates 36 percent
of the disk.
You’ll find a crescent
Moon nearby February 25 and
26 (with a phase of 20 percent
and 11 percent, respectively).
Mercury also appears in
the morning sky late in the
month, but it presents more
of a challenge than it did on
early February evenings. On
the 27th, the innermost planet
shines at 1st magnitude some
9° to the lower left of the wan-
ing crescent Moon. Binocu-
lars offer you the best chance
to spy the elusive planet.
February provides a golden
opportunity for observers to
spot a high-numbered asteroid.
On the 5th, point your tele-
scope at 3rd-magnitude Zeta
(ζ) Tauri, the southern horn of
Taurus the Bull. The closest
point of light in your eyepiece
will be asteroid 532 Herculina.
This main-belt asteroid remains
a short hop away on other early
February nights. While you’re in
the area, stop by the Crab Neb-
ula (M1). A 4-inch instrument
will reveal this supernova rem-
nant’s diffuse form.
German astronomer Max
Wolf discovered Herculina on
April 20, 1904, by noticing its
displacement on images taken
a few nights apart. You can use
a similar technique to identify
the space rock by making a
quick sketch of the field and
returning a night or two later to
see which dot changed place.
Herculina reaches 10th mag-
nitude only when its orbit car-
ries it close to Earth. It happens
this year and next, but after that
not until 2019. Herculina spans
nearly 130 miles, which places it
around 20th in size among all
asteroids. It doesn’t reflect as
much light as typical asteroids,
however, which is why astrono-
mers discovered many smaller
ones before Herculina.
LOCATINGASTEROIDS
Herculina on display in Taurus the Bull
The brightest planet peaks at magnitude –4.9 in mid-February, when
observers under dark skies might see it cast a shadow. ASTRONOMY: ROEN KELLY
Although Herculina wasn’t among the first 500 asteroids discovered, it’s
bright enough this month to spy through a small scope. ASTRONOMY: R O EN K EL LY