Sky & Telescope - USA (2020-01)

skyandtelescope.com • JANUARY 2020 47

Algedi) and then entering Aquarius,
where it has a very close encounter with
Neptune. Almost 12 magnitudes fainter
than Venus, Neptune’s tiny disk is just
2.2′′ wide and should be discernible in
telescopes in good seeing conditions.
That little aqua blip is only about 10′
lower right of Venus at nightfall on
January 27th for viewers along the
East Coast, with a little more distance
separating the two planets for viewers
farther west in North America.
Uranus, two magnitudes brighter
than Neptune, is high in the south in
Aries at nightfall. Detailed fi nder charts
for Uranus and Neptune are in the
September 2019 issue and can also be
accessed at https://is.gd/urnep.
Mercury goes through superior con-
junction with the Sun on January 10th.
It begins to come into view extremely
low in the southwest about 30 min-
utes after sunset in the fi nal days of
the month. As January ends, Mercury
shines at magnitude –1.0 and sets about
70 minutes after the Sun.

PRE-DAWN AND DAWN
Mars rises about three hours before the
Sun in January and cuts an interesting
path through Scorpius and Ophiuchus
during the month. Mars begins the
month and year some 4° to 5° upper
right of the wide double star Beta (β)
Scorpii (Graffi as). The highlight of
Mars’s trek through the stars this month
occurs on the mornings of January 17th

and 18th, when it passes less than 5°

northwest of Antares, the heart of Scor-

pius. At this conjunction of the orange-

gold planet and orange-gold star, Mars

shines at magnitude 1.5, a half-magni-

tude dimmer than Antares. Mars bright-

ens and grows slightly during January,

but even at month’s end its 93%-lit disk

in telescopes is only 4.8′′ wide.

Jupiter passed directly behind the

Sun’s disk at superior conjunction on

December 27, 2019, and is only a few

degrees from the Sun, lost in the solar

glare, as 2020 begins. Not until the

second week of January does Jupiter

become visible to the naked eye before

sunrise. Magnitude –1.9 Jupiter comes

up more than 1½ hours before the Sun

as January ends.

Saturn makes a rare passage directly

behind the Sun’s disk on January 13th,

reaching conjunction with the Sun just

two hours after Pluto does. Saturn,

shining at magnitude 0.6, may be visible

to exceptionally well-placed binocular

observers at month’s end, rising about

an hour before sunup.

EARTH AND MOON

Earth arrives at perihelion, a minimum

of 0.9832 a.u. from the Sun, at 8h UT

on January 5th.

The Moon is waxing gibbous and

3° to 4° left or upper left of Aldeba-

ran at nightfall on January 7th. The

Moon undergoes a penumbral eclipse,

mostly visible in the Eastern Hemi-

sphere on January 10th (see page 50 for

details), and rises only a few degrees

lower right of Pollux at nightfall that

evening across North America. On the

American morning of January 20th, the

waning lunar crescent forms a com-

pact pattern with Mars and Antares. At

nightfall on January 27th, the waxing

lunar crescent is some 6° below Venus,

and the next night approximately the

same distance upper left of Venus.

¢FRED SCHAAF had the 10-mile-wide

asteroid 7065 Fredschaaf named after

him in November 2016.

Jupiter

Saturn

Uranus

Neptune Mercury

Venus

Earth

Mars

March

equinox

June

solstice

December

solstice

Sept.

equinox

Sun

ORBITS OF THE PLANETS

The curved arrows show each planet’s movement during January. The outer planets don’t

change position enough in a month to notice at this scale.

Dusk, Jan 10

45 minutes after sunset

Fomalhaut

Venus

Looking Southwest

b Cap

Dusk, Jan 26 – 28

30 minutes after sunset

Fomalhaut

Mercury

Venus

Moon

Jan 26

Moon

Jan 27

Moon

Jan 28

Looking Southwest