SOUTHERN SKY
November 2019
Mercury transits the Sun
Four planets adorn the
western evening sky
early this month. The constella-
tion Scorpius the Scorpion
joins the scene, looking like it
wants to devour a pair of them
as it dives toward the horizon.
The brighter of the two
lower planets is Venus, which
shines at magnitude –3.8 and
looks like a beacon in the twi-
light. The planet’s eastward
motion this month sets up a
series of nice conjunctions. On
November 4, it passes midway
between Beta (β) and Delta (δ)
Scorpii. It then slides 4° north
of Antares on the 9th and 1.4°
south of Jupiter on the 24th.
Venus remains disappointing
when viewed through a tele-
scope, however, showing an
11"-diameter, nearly full disk.
Mercury serves as Venus’
companion in early November.
On the 1st, the innermost
planet shines at magnitude 0.5
from a perch 3° to the lower left
of its neighbor and a healthy 9°
above the horizon 45 minutes
after sunset. A telescope reveals
Mercury’s beautiful crescent
shape on a disk that spans 9".
The inner world disappears
in twilight within a week as it
heads toward inferior conjunc-
tion on the 11th. But it brief ly
reappears that day when it
passes directly in front of the
Sun for the first time since May- You’ll need a telescope to
view this transit, but make sure
to protect your eyesight by
placing a safe solar filter over
your instrument’s front end.
Mercury appears just 10" across
and looks tiny on the Sun’s
1,939"-diameter disk. Obser vers
in South America can witness
the entire transit, while those
in Africa get to see the initial
stages before sunset. The tran-
sit runs from 12h35m UT to
18h04m UT.
Look higher in the western
sky after sunset and you can’t
miss Jupiter. The giant world
shines at magnitude –1.9 against
the background stars near the
Ophiuchus-Sagittarius border.
It makes a striking pair with
brilliant Venus for a few days
centered around November 24.
Jupiter always looks great
through a telescope. Its disk
measures 32.7" across the equa-
tor and 30.5" through the poles
in mid-November. This polar
f lattening — a result of the
planet’s rapid rotation — is easy
to notice once you know to
look for it. You also should see
two parallel dark cloud belts
that sandwich a brighter zone
coinciding with the equator.
Above the cloud tops, Jupiter’s
Galilean moons dance around
the planet, changing positions
noticeably from night to night.
Scan 20° to Jupiter’s upper
right and you’ll encounter
Saturn. The golden-colored
planet shines at magnitude 0.6
in eastern Sagittarius, a con-
stellation whose brightest stars
appear noticeably fainter than
the ringed world.
Like Jupiter, Saturn shows
distinct polar flattening. At
midmonth, its equatorial diam-
eter of 15.7" is 1.3" greater than
its polar diameter. But the realreason to point a telescope at
Saturn is to view its gorgeous
rings. They currently span 36"
and tip 25° to our line of sight.
This large tilt makes now an
ideal time to see ring structure.
Look for the dark Cassini
Division that separates the
outer A ring from the brighter
B ring. Any telescope also
reveals the 8th-magnitude
moon Titan; a 10-centimeter
instrument brings in three
more 10th-magnitude satellites.
The waxing crescent Moon
adds a sparkle to the western
evening sky during November’s
final week. Luna appears
slightly below Jupiter on the
28th and stands midway
between Venus and Saturn
the following evening.
Mars returns to view before
dawn during the second half of
November. By the 30th, it rises
about 90 minutes before the
Sun and climbs 6° above the
eastern horizon an hour before
sunup. You may need binocu-
lars to see the magnitude 1.7
planet against the twilight.The starry sky
Several years ago, I had a pleas-
ant trip to Cape Town, South
Africa. A highlight was a cable-
car ride to the summit of Table
Mountain overlooking the city.
I was rewarded with spectacu-
lar views of the city and sur-
rounding ocean.
While I was looking down, I
ref lected on the fact that I was
standing atop the only geo-
graphical feature after which a
constellation is named. Mensathe Table Mountain resides
deep in the southern sky,
between declinations of about
–70° to –85°, so it is visible
throughout the night at all
times of the year. French
astronomer Nicolas Louis de
Lacaille introduced this con-
stellation in the 18th century.
Table Mou nt a i n played a
pivotal role in 18th-century
earth sciences, leading to the
erroneous conclusion that our
planet is pear-shaped. Lacaille
sought to measure the distance
over which a particular differ-
ence in latitude occurred, a
technique used to determine
Earth’s curvature. But the grav-
itational attraction of Table
Mountain affected his observa-
tions. Decades later, astrono-
mer Thomas Maclear redid
Lacaille’s measurements and
showed they were off, returning
Earth to a spherical shape.
The constellation’s main
claim to fame is that part of the
Large Magellanic Cloud (LMC),
the Milky Way’s largest satellite
galaxy, occupies its northern
section. Several nice deep-sky
objects — especially star clus-
ters — lie in that direction.
The rest of this little constel-
lation is far from exciting, save
for a curious object located 6°
from the South Celestial Pole.
The 11th-magnitude globular
cluster NGC 1841 is an LMC
outlier and visible as a tiny
patch of light through 15-cm
and larger telescopes. To find it,
start at 6th-magnitude Xi (ξ)
Mensae and then star-hop 1.6°
to the south-southwest.