Sky & Telescope - December 2020 - 46

DECEMBER 2020 OBSERVING
Sun, Moon & Planets by Fred Schaaf
To find out what's
visible in the sky from
your location, go to
skyandtelescope.org.

A Very Rare Jupiter and Saturn Pairing
The gas giant planets are at their closest since 1623.

O

n the evening of December 21st,
Jupiter and Saturn have their closest conjunction in almost 400 years,
and their closest viewable pairing in
nearly 800 years. The giant planets
are less than 1° apart for most of the
month and high enough at dusk for
reasonable views.
In addition to a far-south total
eclipse of the Sun and favorable Geminid meteor shower, in December Mars
is high after nightfall and remains
above the 10″-diameter threshold for
one final month. Finally, long after
Mars sets, brilliant Venus rises in the
morning sky.

DUSK TO EARLY EVENING
Jupiter and Saturn set about 3½ hours
after the Sun as December begins, and
about 1¾ hours after sunset as the

Dusk, Dec 4
45 minutes after sunset

` Cap

_ Cap

month ends. The two planets cross the
border from Sagittarius into Capricornus - first Saturn (on the 15th) followed by Jupiter (on the 18th).
Jupiter and Saturn begin December a
little more than 2° apart and are within
1° of each other from the 12th through
the 29th. But the big event occurs on
the evening of the 21st. That's when
Jupiter and Saturn are separated by a
mere 6′. For observers at mid-northern
latitudes, the two planets will stand
roughly 14° above the southwest horizon 45 minutes after sunset on that
date. Jupiter is at magnitude -2.0 and
33″ wide, while Saturn shines at magnitude +0.6 and 15″ across, with its rings
spanning 35″. At their closest, the two
planets appear separated by less than
12 Jupiter widths. Through a telescope
at moderate magnification, you can fit
WTX 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.

both gas giants and their brighter satellites all together in a single view.
How rare is this month's conjunction? According to calculator extraordinaire Steve Albers, the last Jupiter/Saturn pairing that was closer and readily
observable (49° from the Sun) occurred
in 1226. The closest of all planetary
conjunctions is a mutual occultation, in
which the disk of one planet passes in
front of the other. Albers has turned up
a few mutual occultations of Jupiter and
Saturn, with the most "recent" one he's
found occurring about 8,000 years ago.
Does the 7 BC triple conjunction of
Jupiter and Saturn (during which the
planets passed near each other three
times) account for the Star of Bethlehem? In recent decades, many researchers (including me) have come to favor
the triple conjunction of Venus and

Dawn, Dec 11 - 13
30 minutes before sunrise

Dawn, Dec 6 -7

10°

1 hour before sunrise

Saturn
Jupiter

Moon
Dec 12

LEO

Venus

S A G I T TA R I U S

Moon
Dec 7

Regulus

Looking Southwest

46

DECEMBER 2 02 0 * SK Y & TELESCOPE

Sickle
β Sco
Moon
Dec 6

Looking Southwest, high in the sky

Moon
Dec 13

Looking Southeast

Moon
Dec 11


http://www.skyandtelescope.org

Sky & Telescope - December 2020

Table of Contents for the Digital Edition of Sky & Telescope - December 2020

Contents
Sky & Telescope - December 2020 - Cover1
Sky & Telescope - December 2020 - Cover2
Sky & Telescope - December 2020 - 1
Sky & Telescope - December 2020 - Contents
Sky & Telescope - December 2020 - 3
Sky & Telescope - December 2020 - 4
Sky & Telescope - December 2020 - 5
Sky & Telescope - December 2020 - 6
Sky & Telescope - December 2020 - 7
Sky & Telescope - December 2020 - 8
Sky & Telescope - December 2020 - 9
Sky & Telescope - December 2020 - 10
Sky & Telescope - December 2020 - 11
Sky & Telescope - December 2020 - 12
Sky & Telescope - December 2020 - 13
Sky & Telescope - December 2020 - 14
Sky & Telescope - December 2020 - 15
Sky & Telescope - December 2020 - 16
Sky & Telescope - December 2020 - 17
Sky & Telescope - December 2020 - 18
Sky & Telescope - December 2020 - 19
Sky & Telescope - December 2020 - 20
Sky & Telescope - December 2020 - 21
Sky & Telescope - December 2020 - 22
Sky & Telescope - December 2020 - 23
Sky & Telescope - December 2020 - 24
Sky & Telescope - December 2020 - 25
Sky & Telescope - December 2020 - 26
Sky & Telescope - December 2020 - 27
Sky & Telescope - December 2020 - 28
Sky & Telescope - December 2020 - 29
Sky & Telescope - December 2020 - 30
Sky & Telescope - December 2020 - 31
Sky & Telescope - December 2020 - 32
Sky & Telescope - December 2020 - 33
Sky & Telescope - December 2020 - 34
Sky & Telescope - December 2020 - 35
Sky & Telescope - December 2020 - 36
Sky & Telescope - December 2020 - 37
Sky & Telescope - December 2020 - 38
Sky & Telescope - December 2020 - 39
Sky & Telescope - December 2020 - 40
Sky & Telescope - December 2020 - 41
Sky & Telescope - December 2020 - 42
Sky & Telescope - December 2020 - 43
Sky & Telescope - December 2020 - 44
Sky & Telescope - December 2020 - 45
Sky & Telescope - December 2020 - 46
Sky & Telescope - December 2020 - 47
Sky & Telescope - December 2020 - 48
Sky & Telescope - December 2020 - 49
Sky & Telescope - December 2020 - 50
Sky & Telescope - December 2020 - 51
Sky & Telescope - December 2020 - 52
Sky & Telescope - December 2020 - 53
Sky & Telescope - December 2020 - 54
Sky & Telescope - December 2020 - 55
Sky & Telescope - December 2020 - 56
Sky & Telescope - December 2020 - 57
Sky & Telescope - December 2020 - 58
Sky & Telescope - December 2020 - 59
Sky & Telescope - December 2020 - 60
Sky & Telescope - December 2020 - 61
Sky & Telescope - December 2020 - 62
Sky & Telescope - December 2020 - 63
Sky & Telescope - December 2020 - 64
Sky & Telescope - December 2020 - 65
Sky & Telescope - December 2020 - 66
Sky & Telescope - December 2020 - 67
Sky & Telescope - December 2020 - 68
Sky & Telescope - December 2020 - 69
Sky & Telescope - December 2020 - 70
Sky & Telescope - December 2020 - 71
Sky & Telescope - December 2020 - 72
Sky & Telescope - December 2020 - 73
Sky & Telescope - December 2020 - 74
Sky & Telescope - December 2020 - 75
Sky & Telescope - December 2020 - 76
Sky & Telescope - December 2020 - 77
Sky & Telescope - December 2020 - 78
Sky & Telescope - December 2020 - 79
Sky & Telescope - December 2020 - 80
Sky & Telescope - December 2020 - 81
Sky & Telescope - December 2020 - 82
Sky & Telescope - December 2020 - 83
Sky & Telescope - December 2020 - 84
Sky & Telescope - December 2020 - Cover3
Sky & Telescope - December 2020 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/newtrack/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com