Sky & Telescope - March 2019 - 55

JIM MISTI

eyes. NQ Gem exhibits low-amplitude
brightness variations caused by intrinsic
pulsations of the star and interactions
with its white dwarf companion.
Resting north-northwest of Delta
(δ) Gem, the ﬂat galaxy NGC 2357 is
a challenging target. Flat galaxies are
disk-like galaxies that have little or no
central bulge and are seen edge-on from
our vantage point, making them look
very slender. My 10-inch reﬂector at
299× shows a very faint needle of light
with a slightly brighter center and a
13th-magnitude star perched north of
its north-northwestern end. It's easier
to capture with my 15-inch scope at
216× but still dim enough to be best
studied with averted vision. It's hard to
tell exactly where the needle's tips fade
into the background sky, but I'd put
the length at at least 2′. NGC 2357 has
hosted two supernovae: One peaked at
magnitude 14.0 in the year 2015 and
the other at magnitude 15.3 in 2010.
8h 00m

N
E

p Most amateur scopes reveal the central
region of the bipolar planetary nebula NGC
2371/72; the outer arcs are difficult to see and
call for more aperture. Look for the bright knot
of gas - likely a jet - in the northwest end of
the southwest lobe of the nebula. A similar but
less vivid knot lies in the southeast end of the
northeast lobe. An O III filter can help.

The planetary nebula NGC 2392
sits east-southeast of Delta Gem and is
easily recognized in the 130-mm scope
at 37×. It's small, bright, and bluish,
with its central star plainly visible. At

7h 30m
Castor

W
S

7h 00m

θ

6h 30m
2274

α ρ

IC 2199

+30°

ι

Pollux

β
+25°

2487
2481

τ

2371/72

σ

2331
2266

υ
GEMINI

κ

ε

Star magnitudes

"Two faint of an equal size, both small
within a minute of each other; each has
a seeming nucleus, and their apparent
atmospheres run into each other." The
halves received consecutive numbers in
the New General Catalogue of Nebulae
and Clusters of Stars (NGC).
In the 130-mm scope at 102×, NGC
2371/72's oblong mist shines brighter
in the southwest. At 164× I can just
tell that the nebula is bipolar and a
little less than 1′ long. Adding a narrowband ﬁlter brings out a bright spot
in the northwest end of the southwest
lobe. Through my 14.5-inch scope
at 276×, the lobes are detached with
faint nebulosity between them and
some ﬂuff to their sides. The nebula is
brightest around the southwest lobe's
spot. Although not as bright, there's a
corresponding spot in the southeast end
of the northeast lobe, such that a line
between the two spots would run diagonally across the nebula and through
the dim central star. Images display
outrigger arcs bracketing the main body
of NGC 2731/32, making the nebula
resemble a candy in a cellophane twistwrap. Visually I see a short piece of the
northwest arc, and with a narrowband
ﬁlter I can glimpse a bit of the southeast arc with difﬁculty. The lobe's spots
stand out very well with an O III ﬁlter.
The bright spots in NGC 2371/72
are knots of gas ejected by the central
star, which is growing ferociously hot
as it collapses to eventually become a
white dwarf, its surface currently blazing about 23 times as hot as our Sun's.
As with most planetary nebulae the
distance is poorly known, but recent
estimates give about 4,000 or 5,000
light-years.
West of Kappa (κ) Geminorum, the
carbon star NQ Gem offers us a nice
color comparison with HD 60336 (HIP
36883), a normal red giant star 44′ to
its east-southeast. Seen in the same
ﬁeld of view through the 130-mm scope
at 37×, the "red" giant is only orange,
while NQ Gem is distinctly red-orange.
A carbon star's atmosphere is rich in
carbon-bearing molecules that absorb
the shorter wavelengths of visible light,
leaving only ruddy colors to reach our

1
2
3
4
5
6

NQ
2357

δ
+20°

2420

ζ

2392

ν

2342
2339
2418

λ
γ

+15°
2355
Abell 21

2395

ξ
+10°

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Sky & Telescope - March 2019

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