Sky & Telescope - January 2024 - 56

JANUARY 2024 OBSERVING
Suburban Stargazer
2
1
3
4
5
6
7
8
9
5h 10m
5h 00m
ORION
1637
µ
68
β
τ
ψ
β
Rigel
λ
47
Σ636
Σ649
63
LEPUS
ι
-12°
ν
κ
λ
Zaurak
Hind's Crimson Star
53
R(c)
pWINDING RIVER Eridanus flows in a sinuous fashion east and southeast away from Orion and toward the south horizon. This month's tour will
guide you to several colorful double stars, including an exotic triple system that features tandem red and white dwarf stars. At the south end of the
fishing expedition is a prize catch - the bright planetary nebula NGC 1535.
(λ) Eridani. Lambda is a stepping stone
to a double called Struve 649 (Σ649),
13′ to the west-northwest. The purewhite
primary of Σ649 is magnitude
5.8, and the distinctly reddish-orange
secondary sun 21.3″ northeast is magnitude
9.0. From Σ649, a 13′ nudge due
west captures a much tighter binary
designated Σ636. Its 7.1- and 8.5-magnitude
pinpoints, just 3.7″ apart, resolve
faintly yet cleanly in my refractor at
100×. The compact components of Σ636
are pristine in the reflector.
A meandering star-hop gets us to
the next fishing hole on my Eridanus
angling trip. First, we hop northward
back to Cursa. At Cursa, we head west
3¾° to 4.3-magnitude Omega (ω), then
go northwest almost 3° to 4.0-magnitude
Mu (μ), then west again for 2¼°
to 3.9-magnitude Nu (ν), and finally 7°
southwest to 4.0-magntiude Omicron1
56 JANUARY 2024 * SKY & TELESCOPE
(ο1) Eridani. The total trip westward to
Omicron1 is about 14°, but you'll find
the route easy to follow in an optical
finder. If your sky is better than mine,
you can star-hop the whole way using
your bare eyes and a red-dot (or similar)
aiming device.
Observe Omicron1 Eridani in a
finderscope, or in a wide-field telescope
at low magnification, and you'll
discover it's flanked by 5.4-magnitude
37 Eridani, 1
in the water slaking its thirst. Celestial
mythology is never short of tall tales.
Astronomers know Omicron2 as
/3° roughly westward, and
4.4-magnitude Omicron2 Eridani, a
bit more than 1° to the southeast. The
threesome forms a shallow triangle that
resembles the constellation Aries. In
Arabic star lore, the two Omicrons were
named Beid (the Eggs) and Keid (the
Egg Shells). According to legend, the
eggy Beid and Keid belonged to a couple
of lanky ostriches - one relaxing on the
riverbank, the other standing knee-deep
40 Eridani. Just 16.3 light-years away,
40 Eridani displays significant proper
motion across the sky, shifting approximately
4″ per year. Moreover, 40 Eridani
is an exotic multiple system. The yellowy
primary, 40 Eri A, sports a wide,
9.3-magnitude attendant, 40 Eri B,
82.7″ eastward. That 9.3-magnitude dot
is actually the combined light of two
stars: a 9.5-magnitude white dwarf, 40
Eri B, and an 11.2-magnitude red dwarf,
40 Eri C. Currently, the red and white
siblings stand 7.9″ apart - essentially
their greatest separation in over two
centuries. The diminutive duo is perfect
in my reflector at 135×. In my apochromat
at 200×, the white dwarf shines
easily through the city murk (it's the
most accessible white dwarf for back-14°
γ
64
1535
ERIDANUS
39
BM
-10°
ο2
40
Keid
-8°
66
1700
Cursa
ω
-6°
Beid
ο1
37
1600
ν
ξ
-4°
4h 50m
4h 40m
51
4h 30m
4h 20m
4h 10m
35
4h 00m
-2°
Star magnitudes

Sky & Telescope - January 2024

Table of Contents for the Digital Edition of Sky & Telescope - January 2024