SOUTHERN SKY BY MARTIN GEORGE
March 2020
Venus at its evening best
The March evening
sky harbors just one
naked-eye planet, but what a
planet it is: Venus brightens
from magnitude –4.3 to –4.5
this month, shining nearly
10 times brighter than any
other point of light in the sky.
You can find the brilliant world
gleaming in the northwest soon
after sunset. Venus reaches
greatest elongation March 24,
when it lies 46° east of the Sun
and stands some 15° high a
half-hour after sundown.
It doesn’t climb higher
because the ecliptic — the
apparent path of the Sun across
the sky that the planets closely
follow — makes a shallow angle
to the western horizon after
sunset from the Southern
Hemisphere at this time of year.
By the end of March, Venus
crosses from Aries into Taurus
and pulls within 3° of the glori-
ous Pleiades star cluster.
Despite its low altitude,
Venus looks grand when
viewed through small tele-
scopes. (Try to view it during
twilight, when the contrast
between sky and planet is less.)
By March 27, the planet’s diam-
eter swells to 24" while its phase
wanes to 50 percent lit.
After Venus sets, we have to
wait several hours for more
planets appear. Still, it’s worth
getting up early to see Mars,
Jupiter, and Saturn. During
the first half of March, the trio
appears against the backdrop of
Sagittarius, strung out in a line
from upper left (Mars) to lower
right (Saturn).All three worlds move east-
ward relative to the background
stars at different rates. Mars,
being closest to the Sun, travels
fastest. It passes 0.7° south of
Jupiter on March 20 and 0.9°
south of Saturn on the 31st.
The latter conjunction occurs
in Capricornus; Saturn crossed
the border into the Sea Goat on
the 21st while Mars followed
on the 30th.
Mars remains a disappoint-
ing telescopic sight. With an
apparent diameter of only 6", it
reveals few, if any, details. The
best day to view Mars, at least if
you live in far southern South
America, is March 18, when a
31-percent-lit waning crescent
Moon occults the planet. From
Punta Arenas, Chile, Mars dis-
appears behind the Moon’s
bright limb at 6h44m UT and
reappears from behind the dark
limb at 7h39m UT.
Jupiter ranks as the bright-
est of the morning planets. The
giant world shines at magni-
tude –2.0 in mid-March and
appears far brighter than any
other point of light in the pre-
dawn sky. When viewed
through a telescope, Jupiter
spans 35" and shows a wealth
of detail in its dynamic atmo-
sphere. Also watch the four
bright Galilean satellites as
they shift position from night
to night.
While you have your tele-
scope out, be sure to nudge it
eastward to Saturn. If any-
thing, this magnitude 0.7
planet looks better than Jupiter.
Even the smallest scope revealsthe planet’s 16"-diameter disk
surrounded by a spectacular
ring system than spans 36" and
tilts 21° to our line of sight. You
also should see 8th-magnitude
Titan, Saturn’s biggest and
brightest moon.
The morning show doesn’t
end with Saturn. Mercury
climbs away from the Sun on
its way to greatest elongation
March 24. The magnitude 0.2
planet then lies 28° west of the
Sun and appears 15° high in the
east an hour before sunrise.
Compare that with Venus’
lower evening altitude despite
its greater elongation. The rea-
son: The ecliptic angles nearly
straight up from the eastern
horizon on March mornings.
At greatest elongation, a
telescope reveals Mercury’s
7"-diameter disk and roughly
half-lit phase. But the best time
to view the innermost planet
comes during the first half of
March, when it displays a
noticeably larger disk and a
pretty crescent shape.The starry sky
When it comes to constella-
tions, none is bigger than
Hydra the Water Snake. Its
shape extends roughly 100°
from head to tail, stretching
across the March evening sky
from nearly due north to slight-
ly south of due east. Don’t con-
fuse Hydra with its smaller
cousin, Hydrus the Little Water
Snake, which lies deep in the
southern sky.
Most people are unaware
that a feline once appearedwithin the modern confines of
Hydra. French Astronomer
Jérôme Lalande (1732–1807)
invented the constellation Felis
the Cat from a group of faint
stars centered about 10° south-
east of ruddy 2nd-magnitude
Alphard, Hydra’s brightest star.
Felis made it into several
19th-century star atlases, most
notably Johann Bode’s 1801
Uranographia. In describing
Felis, Bode wrote: “This con-
stellation has been only recently
proposed by de la Lande to fill
an empty space that existed in
the middle of the neck of
Hydra.” Of course, no part of
the sky is truly empty, but Felis’
brightest star glows dimly at
5th magnitude — so even a
small amount of light pollution
makes this part of the sky
appear devoid of stars.
British author Alexander
Jamieson included Felis in his
1822 Celestial Atlas. Jamieson
depicted Felis as a somewhat
happier cat than the one Bode
portrayed, which appears to be
annoyed or angry.
Although Felis has long
fallen into disuse, a rather
delightful commemoration
of the constellation took place
in 2018. That’s when the
International Astronomical
Union approved naming the
extinct constellation’s brightest
star, 5th-magnitude HD 85951,
Felis. Whenever I gaze at this
star, I’m reminded that a fourth
cat once existed among the
constellations, joining Leo the
Lion, Leo Minor the Little Lion,
and Lynx the Lynx.