Sky & Telescope - December 2019 - 47

tudes fainter than Venus), and Venus,
Saturn, and Pluto ﬁt together within a
circle just 2½° in diameter.

December
solstice

Earth

EVENING

Uranus

Neptune is at its highest in the south
as evening twilight is ending and
starts setting before midnight. Uranus is highest around mid-evening
and doesn't set until a few hours after
midnight. Finder charts for locating
Neptune and Uranus are in the September issue and can also be accessed at
https://is.gd/urnep.

Sept.
equinox

March
equinox

Jupiter
Neptune
Saturn

Mercury

Sun

Venus

Mars

June
solstice

ORBITS OF THE PLANETS
The curved arrows show each planet's movement during December. The outer planets don't
change position enough in a month to notice at this scale.

EARLY MORNING
AND DAWN
Mars rises less than 3 hours before
the Sun as December opens but more
than 3 hours before the Sun at month's
(and year's) end. Mars brightens a bit
- from magnitude 1.7 to 1.6 - this
month, but its disk is only about 4″
wide. As December begins, Mars is
almost 20° high in the east-southeast
at mid-twilight and shines about
halfway between high Spica and low
Mercury. As the month ends, the Red
Planet is still in Libra, but is nearing
the head of Scorpius.
Mercury was at greatest western
elongation on November 28th but con-

tinues with a ﬁ ne morning apparition
into the opening weeks of December.
Mercury is bright, at magnitude -0.6,
but its rise-time gets rapidly later. As
December starts, the hot little world
rises about 1½ hours before the Sun
but by the 16th only about an hour.
December 16th is also the day that
Mercury, in Scorpius, is 5° northeast
of 1st-magnitude Antares, though the
red supergiant will be hard to see in
the morning twilight. After December 17th, Mercury will be too low in
bright twilight to see.

Dusk, Dec 27- 29

Dawn, Dec 31

30 minutes after sunset

1 hour before sunrise

LIBRA

Moon
Dec 29

α Cap

Venus

β Cap

Moon
Dec 28

Moon
Dec 27

Mars

β Sco

δ Sco

Antares
Saturn

Looking Southwest

Looking Southeast

SUN AND MOON
The Sun reaches the December solstice
at 11:19 p.m. EST on December 21st.
This is the shortest day and the beginning of winter in the Northern Hemisphere and the longest day and the start
of summer in the Southern Hemisphere.
The Sun undergoes an annular
eclipse visible from the Middle East,
India, and Indonesia, with partial
phases visible from most of Asia, northern and western Australia, and parts of
the Paciﬁc (see page 49 for more information on this event).
The Moon is full on December 12th,
largely washing out the peak of the
Geminid meteor shower the next few
nights (but see page 48). On December 22nd the waning lunar crescent is
some 8° to 9° above Mars, the next
morning 5° to 6° lower left of it. On
December 24th, low in the southeast
about 45 minutes before sunrise, a
very thin Moon is several degrees left
or upper left of Antares. On December
27th the very thin waxing Moon is
about 5° upper left of Saturn, which
may be hard to ﬁnd in bright evening
twilight. On the next evening, December 28th, the lunar crescent is spectacularly close to Venus, a bit more than
2° below the planet.
¢ FRED SCHAAF teaches astronomy
at both Rowan University and Rowan
College in Gloucester County, southern
New Jersey.
sk yandtele scope.com * D EC E M B E R 2 019

https://www.is.gd/urnep http://www.skyandtelescope.com

Sky & Telescope - December 2019

Table of Contents for the Digital Edition of Sky & Telescope - December 2019