Sky & Telescope - January 2021 - 46

JANUARY 2021 OBSERVING
Sun, Moon & Planets by Gary Seronik
To find out what's
visible in the sky from
your location, go to
skyandtelescope.org.

Goodbye Jupiter and Saturn (and Mars)
A trio of prime telescopic planets reaches notable milestones.
FRIDAY, JANUARY 1
Going, going, going . . . . As the month
opens, Jupiter and Saturn remain
tightly paired low in the southwest
at dusk, but they're slowly drifting
apart while they set earlier and earlier.
The duo is separated by just 1¼° this
evening and are going to be a particularly striking sight in binoculars or a
small, low-power telescope, both of
which should add a couple of Jupiter's
moons to the scene. (Look for Callisto,
and perhaps Ganymede and Io, to the
planet's left.) The gas giant pair will
remain within 2° of each other until
the 8th.

MONDAY, JANUARY 4
This date marks a signiﬁcant milestone
in the current Mars apparition. For
the ﬁrst time since last June, the Red
TX These scenes are drawn for near the
middle of North America (latitude 40° north,
longitude 90° west); European observers
should move each Moon symbol a quarter of
the way toward the one for the previous date.

Planet's disk will span less than 10″. So
what? Although it's largely an arbitrary
distinction, most Mars-watchers regard
crossing the 10″ threshold as the point
at which signiﬁcant surface detail is no
longer readily visible in moderate-size
telescopes. In many respects this event
marks the conclusion of the 2019-20
Mars season for all but the most dedicated planetary observers. And given its
decline in prominence - Mars is just
one-tenth as bright as it was at its peak
last October - the winding down of the
planet's remarkable run is obvious even
to the naked eye.
Although it's a diminished telescopic
target, Mars isn't going away anytime
soon. It will continue to adorn the
evening sky through July but won't be in
conjunction with the Sun until October
- that's when the current apparition

ﬁnally concludes and a new one begins.
We'll have to wait until September 2022
before the Martian disk once again
exceeds 10″.

SATURDAY, JANUARY 9
Very low in the west-southwest during evening twilight there's a planetary
three-for-one, as Jupiter and Saturn
are joined by Mercury to form a tight
right triangle. Mercury is a bit more
than 1½° from Saturn, which itself is
roughly 2¼° from Jupiter. Given their
very low altitude, it's likely you'll need
binoculars (and a very clear sky) to see
all three objects, with Saturn being
the faintest and most difﬁcult to pick
out. On the following night (the 10th),
Mercury will be halfway between the
other two planets, and then on the 11th
it will pull up alongside Jupiter.

Dusk, Jan 9

Dawn, Jan 9 -11

30 minutes after sunset

30 minutes before sunrise

Moon
Jan 9

Dusk, Jan 1
45 minutes after sunset

SCORPIUS

CAPRICORNUS
Moon
Jan 10

10°

Antares

CAPRICORNUS
Jupiter
Saturn

Mercury

Looking Southwest

46

JANUARY 2 021 * SK Y & TELESCOPE

Moon
Jan 11

Jupiter
Saturn

Looking West-Southwest

Venus

Looking Southeast
http://www.skyandtelescope.org
Sky & Telescope - January 2021

Table of Contents for the Digital Edition of Sky & Telescope - January 2021
