Sky & Telescope - September 2021 - 48
Star magnitudes
NEPTUNE / TRITON MONTAGE: NASA / JPL /
USGS; PALLAS PAIR: ESO / VERNAZZA ET AL
SEPTEMBER 2021 OBSERVING
Celestial Calendar by Bob King
Neptune
and Pallas
Pal Up at
Opposition
The big blue planet and a big
asteroid put on a show.
N
eptune reaches opposition on
September 14th in the star-sparse
wilds of eastern Aquarius, near the Circlet
of Pisces. Despite being more than
4.3 billion kilometers (2.7 billion miles)
away, the solar system's most remote
major planet shines at magnitude 7.8,
which means you can claim it with
10×50 binoculars from any reasonably
dark location.
As if to avoid the astronomical
paparazzi, the distant blue world stays
clear of any bright stars that could
easily give away its location as it slowly
treks westward in retrograde motion.
As the chart opposite shows, only a
couple of 6th-magnitude stars mark its
path during the current apparition. I
recommend trying to catch
Neptune on the night of
September 23-24 when
it glides just 1.6′ south of
6.3-magnitude HD 221148.
One of my favorite Neptunian
observing activities
is tracking down its largest
These high-resolution images
of the north (top) and south (bottom)
hemispheres of Pallas were
made with the SPHERE imager
on the Very Large Telescope in
2020. Numerous craters in both
hemispheres give the asteroid a
dimpled appearance, making it
resemble a giant golf ball.
48 SEPTEMBER 2021 * SKY & TELESCOPE
In this computer-generated montage made from Voyager 2 images, Triton (foreground)
and Neptune appear as they might through the window of an approaching spacecraft.
The dark streaks across Triton's south polar cap are thought to be due to recent, geyserlike
eruptions that spewed dust and ice across the moon's surface.
moon, Triton. It's the only large satellite
that orbits backwards (in retrograde)
around its host planet. That oddity and
a composition similar to Pluto's suggest
that Triton may be a captured dwarf
planet from the Kuiper Belt. When it's
at its greatest elongation from Neptune,
the 13.5-magnitude moon is readily
seen in 10-inch or larger telescopes
used at magnifications around 200×.
Triton's distance from Neptune varies
this season from about 9.5″ to 17.0″. To
locate it, use the online Triton Tracker,
found in the Tools section at
skyandtelescope.org.
From Neptune it's a short
hop northwest to 2 Pallas.
As its designation would
suggest, Pallas was the second
asteroid discovered, and
it's the third largest, with a
mean diameter of roughly
513 kilometers. Pallas comes
to opposition on the night
of September 10-11, when
it shines at magnitude 8.5
- within range of 10×50
binoculars under a dark
sky. Pallas begins Septemω
λ
0°
ι
κ
Path
of
2 Pallas
AQUARIUS
Path of
Neptune
-10°
0h 00m
23h 30m
φ
ψ ψ1
2
23h 00m
τ
ber 1.6° south-southwest of 3.7-magnitude
Gamma (γ) Piscium and ends
the month 2.9° north-northeast of
3.7-magnitude Lambda (λ) Aquarii.
At this year's opposition, Pallas
beckons from a relatively remote 320.5
million kilometers away. During closer
oppositions it can reach magnitude 6.6,
which means that under exceptional
skies it's bright enough to see without
optical aid. We'll next get that chance
in March 2028.
If Pallas has whetted your asteroid
appetite, you have an excellent shot at
λ
θ PISCES
γ
2
3
4
5
6
http://www.skyandtelescope.org
Sky & Telescope - September 2021
Table of Contents for the Digital Edition of Sky & Telescope - September 2021
Contents
Sky & Telescope - September 2021 - Cover1
Sky & Telescope - September 2021 - Cover2
Sky & Telescope - September 2021 - 1
Sky & Telescope - September 2021 - Contents
Sky & Telescope - September 2021 - 3
Sky & Telescope - September 2021 - 4
Sky & Telescope - September 2021 - 5
Sky & Telescope - September 2021 - 6
Sky & Telescope - September 2021 - 7
Sky & Telescope - September 2021 - 8
Sky & Telescope - September 2021 - 9
Sky & Telescope - September 2021 - 10
Sky & Telescope - September 2021 - 11
Sky & Telescope - September 2021 - 12
Sky & Telescope - September 2021 - 13
Sky & Telescope - September 2021 - 14
Sky & Telescope - September 2021 - 15
Sky & Telescope - September 2021 - 16
Sky & Telescope - September 2021 - 17
Sky & Telescope - September 2021 - 18
Sky & Telescope - September 2021 - 19
Sky & Telescope - September 2021 - 20
Sky & Telescope - September 2021 - 21
Sky & Telescope - September 2021 - 22
Sky & Telescope - September 2021 - 23
Sky & Telescope - September 2021 - 24
Sky & Telescope - September 2021 - 25
Sky & Telescope - September 2021 - 26
Sky & Telescope - September 2021 - 27
Sky & Telescope - September 2021 - 28
Sky & Telescope - September 2021 - 29
Sky & Telescope - September 2021 - 30
Sky & Telescope - September 2021 - 31
Sky & Telescope - September 2021 - 32
Sky & Telescope - September 2021 - 33
Sky & Telescope - September 2021 - 34
Sky & Telescope - September 2021 - 35
Sky & Telescope - September 2021 - 36
Sky & Telescope - September 2021 - 37
Sky & Telescope - September 2021 - 38
Sky & Telescope - September 2021 - 39
Sky & Telescope - September 2021 - 40
Sky & Telescope - September 2021 - 41
Sky & Telescope - September 2021 - 42
Sky & Telescope - September 2021 - 43
Sky & Telescope - September 2021 - 44
Sky & Telescope - September 2021 - 45
Sky & Telescope - September 2021 - 46
Sky & Telescope - September 2021 - 47
Sky & Telescope - September 2021 - 48
Sky & Telescope - September 2021 - 49
Sky & Telescope - September 2021 - 50
Sky & Telescope - September 2021 - 51
Sky & Telescope - September 2021 - 52
Sky & Telescope - September 2021 - 53
Sky & Telescope - September 2021 - 54
Sky & Telescope - September 2021 - 55
Sky & Telescope - September 2021 - 56
Sky & Telescope - September 2021 - 57
Sky & Telescope - September 2021 - 58
Sky & Telescope - September 2021 - 59
Sky & Telescope - September 2021 - 60
Sky & Telescope - September 2021 - 61
Sky & Telescope - September 2021 - 62
Sky & Telescope - September 2021 - 63
Sky & Telescope - September 2021 - 64
Sky & Telescope - September 2021 - 65
Sky & Telescope - September 2021 - 66
Sky & Telescope - September 2021 - 67
Sky & Telescope - September 2021 - 68
Sky & Telescope - September 2021 - 69
Sky & Telescope - September 2021 - 70
Sky & Telescope - September 2021 - 71
Sky & Telescope - September 2021 - 72
Sky & Telescope - September 2021 - 73
Sky & Telescope - September 2021 - 74
Sky & Telescope - September 2021 - 75
Sky & Telescope - September 2021 - 76
Sky & Telescope - September 2021 - 77
Sky & Telescope - September 2021 - 78
Sky & Telescope - September 2021 - 79
Sky & Telescope - September 2021 - 80
Sky & Telescope - September 2021 - 81
Sky & Telescope - September 2021 - 82
Sky & Telescope - September 2021 - 83
Sky & Telescope - September 2021 - 84
Sky & Telescope - September 2021 - Cover3
Sky & Telescope - September 2021 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202501
https://www.nxtbook.com/nxtbooks/aas/st_202412
https://www.nxtbook.com/nxtbooks/aas/st_202411
https://www.nxtbook.com/nxtbooks/aas/st_202410
https://www.nxtbook.com/nxtbooks/aas/st_202409
https://www.nxtbook.com/nxtbooks/aas/st_202408
https://www.nxtbook.com/nxtbooks/aas/st_202407
https://www.nxtbook.com/nxtbooks/aas/st_202406
https://www.nxtbook.com/nxtbooks/aas/st_202405
https://www.nxtbook.com/nxtbooks/aas/st_202404_qr
https://www.nxtbook.com/nxtbooks/aas/st_202404
https://www.nxtbook.com/nxtbooks/aas/st_202403
https://www.nxtbook.com/nxtbooks/aas/st_202402
https://www.nxtbook.com/nxtbooks/aas/st_202401_aus
https://www.nxtbook.com/nxtbooks/aas/st_202401
https://www.nxtbook.com/nxtbooks/aas/st_202312_aus
https://www.nxtbook.com/nxtbooks/aas/st_202312
https://www.nxtbook.com/nxtbooks/aas/st_202311
https://www.nxtbook.com/nxtbooks/aas/st_202310
https://www.nxtbook.com/nxtbooks/aas/st_202309
https://www.nxtbook.com/nxtbooks/aas/st_202308
https://www.nxtbook.com/nxtbooks/aas/st_202307
https://www.nxtbook.com/nxtbooks/aas/st_202306
https://www.nxtbook.com/nxtbooks/aas/st_202305
https://www.nxtbook.com/nxtbooks/aas/st_202304
https://www.nxtbook.com/nxtbooks/aas/st_202304_qr
https://www.nxtbook.com/nxtbooks/aas/st_202303
https://www.nxtbook.com/nxtbooks/aas/st_202302
https://www.nxtbook.com/nxtbooks/aas/st_202301
https://www.nxtbook.com/nxtbooks/aas/st_202212
https://www.nxtbook.com/nxtbooks/aas/st_202211
https://www.nxtbook.com/nxtbooks/aas/st_202210
https://www.nxtbook.com/nxtbooks/aas/st_202209
https://www.nxtbook.com/nxtbooks/aas/st_202208
https://www.nxtbook.com/nxtbooks/aas/st_202207
https://www.nxtbook.com/nxtbooks/aas/st_202206
https://www.nxtbook.com/nxtbooks/aas/st_202205
https://www.nxtbook.com/nxtbooks/aas/st_202204
https://www.nxtbook.com/nxtbooks/aas/st_202203
https://www.nxtbook.com/nxtbooks/aas/st_202202
https://www.nxtbook.com/nxtbooks/aas/st_202201
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/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