Sky & Telescope - January 2021 - 50

JANUARY 2021 OBSERVING
Celestial Calendar

Shortly after Jupiter occults
44 Capricorni on April 2nd, the
star passes just 0.5″ north of
the Jovian moon Io, as seen
in this simulation.

JANUARY 2 021 * SK Y & TELESCOPE

the third full Moon in a season that
contains four. This is the original (and
largely forgotten) deﬁnition of the Blue
Moon as outlined in the Maine Farmers'
Almanac.
September 14: Neptune is at opposition.
November 4: Uranus is at opposition.
November 19: A near-total lunar
eclipse occurs this morning, visible

Minima of Algol
29
30

PERSEUS
38

Algol

TRIANGULUM

S Perseus is positioned at the zenith during
evening hours in January. Every 2.87 days, Algol (Beta Persei) dips from its usual magnitude
2.1 to 3.4 and back. Use this chart to estimate
its brightness in respect to comparison stars of
magnitude 2.1 (Gamma Andromedae) and 3.4
(Alpha Trianguli).

Dec.
3
6
9
11
14
17
20
23
26
29
31

UT
6:54
3:43
0:32
21:21
18:10
14:59
11:49
8:38
5:27
2:16
23:05

Jan.
3
6
9
12
15
18
21
23
26
29

UT
19:55
16:44
13:33
10:22
7:12
4:01
0:50
21:39
18:29
15:18

These geocentric predictions are from the
recent heliocentric elements Min. = JD
2445641.554 + 2.867324E, where E is any
integer. For a comparison-star chart and
more info, see skyandtelescope.org/algol.

STELL A RIU M

the early morning hours.
July 11: The thin, waning crescent
Moon shines 5° right of Venus and
Mars, which are separated by 1° low in
the western sky at dusk. On the 12th,
Venus and Mars are a scant ½° apart
and shine at magnitudes of -3.9 and
1.8, respectively.
August 2: Saturn is at opposition.
August 12: The Perseid meteor
shower peaks in the predawn hours.
The waxing crescent Moon won't spoil
the view because it sets around 10 p.m.
local daylight time on the 11th. There
might be a few extra meteors visible,
courtesy of Comet Chacornac (C/1852
K1). On August 12th around 4:22 UT,
the Earth will pass very close (15,000
km) to the comet's dust tail. The radiant
for the resulting meteors lies in southeastern Cetus near the star Pi Ceti.
August 18: The variable star Mira
(Omicron Ceti) will be at or near its
maximum brightness of magnitude 3.
August 19: The waxing gibbous Moon
occults Nunki (Sigma Sagittarii) for
observers in the southernmost U.S.,
Central America, and northern South
America.
August 19: Jupiter is at opposition.
August 22: This morning features
a Seasonal Blue Moon, that is,

from the Americas, northern Europe,
east Asia, Australia, and the Paciﬁc. A
full 97.4% of the Moon will dip into
Earth's umbral shadow. The remaining
2.6% of the southern limb will glow
brightly, giving the Moon the appearance of Mars with a polar cap. First
umbral contact is at 2:19 a.m. EST (7:19
UT); greatest eclipse is at 4:03 a.m.; and
the Moon exits the umbra at 5:47 a.m.
November 27: Ceres is at opposition
and shines at magnitude 7.0 in Taurus.
The asteroid spends November crossing
the Hyades and on the night of November 4-5 passes just a few arcminutes
south of Aldebaran.
December 5: Jupiter, Saturn, Venus,
and the Moon form a spectacular 50°long line in the western sky in twilight.
Over the following three evenings, the
Moon will visit each planet in turn.
Towards the end of December, Mercury
joins the gathering.
December 14: The Geminid meteor
shower peaks around 2 a.m. EST
(7 UT), which is nearly ideal for North
American viewers. Unfortunately, the
waxing gibbous Moon (80% illuminated) will spoil the show until it sets
at around 3 a.m. local time. For a few
hours before morning twilight, there
should be some excellent, moonfree
meteor watching.

http://www.skyandtelescope.org/algol

Sky & Telescope - January 2021

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