Sky & Telescope - March 2021 - 63

Star magnitudes

2
3
4
5
6
7

HD 65390

HD 63332

CAM

+55°
7

PuWe 1 δ

JnEr 1

2 HD 43352

+50°

LYNX
AURIGA
8h

Capella

+45°

S MANY MONIKERS The complex processes that sculpt planetary nebulae often give rise to intricate shapes. Everyday objects inspire observers, professionals and amateurs alike, to bestow creative nicknames upon these ethereal targets. And thus JnEr 1 is also known as the Headphone
Nebula. Look some 2.5° northwest of 27 Lyncis to locate this planetary. You'll need a nebula filter and low power to see its faint disk.

STEFA N BINNE WIES / CA PELL A OBSERVATORY

The Elusive Three
The spring sky contains a number of planetary nebulae that
are very challenging. Three of them are presented here to
round out our tour and provide the most adventurous readers
a chance to test their observing skills - only a limited number of successful sightings have ever been reported.
K 2-2 in Monoceros presents a large, extremely faint disk.
Czech astronomer Luboš Kohoutek discovered it on a National
Geographic Society - Palomar Observatory Sky Survey (POSS)
plate in 1963. You'll ﬁnd it 2.8° east of 15 Monocerotis, the
brightest star in NGC 2264, the Christmas Tree Cluster.
Look for a triangle of bright stars: HD 51104 (magnitude
5.9), HR 2555 (6.3), and HD 50005 (6.8), with sides a little
more than a degree in length that show well in the ﬁnder.
The western side of the triangle is bordered by HR 2555 to the
north and HD 50005 to the south. K 2-2 is located along the
line between them about a third of the way from HD 50005.
You'll need low power and a nebula ﬁlter to spy this elusive
disk. Try sweeping across the ﬁeld to detect the subtle change
in brightness as you cross the rim of the planetary.
Even more difﬁcult, perhaps, is PuWe 1 in Lynx. Austrian astronomers Alois Purgathofer and Ronald Weinberger
discovered this planetary in 1980 also on a POSS plate. In
apparent angular size it's the largest planetary known and has
extremely low surface brightness. It's about 1,400 light-years
away and located 3.2° northeast of Delta (δ) Aurigae and 1.2°
southwest of the 5.5-magnitude RR Lyncis. The 15.3-magnitude central star of PuWe 1 is extremely hot and hydrogenrich. PuWe 1 was once considered one of the rare examples of

a triple-star system producing a planetary nebula. However,
two of the stars are now understood to be at a different distance to the nebula and unrelated to its formation. The closest I've come to detecting this huge target was with a 30-inch
f/4.5 Dob. I recorded only a " suspected glow " at 111× with an
Ultra-High Contrast ﬁlter. I've heard from other observers,
however, who have reported a more conﬁdent detection. Give
it a try and if you succeed, I hope you'll let me know.
Another catch logged by only a few observers is LoTr 5.
It, too, was discovered in 1980, by British astronomers
Andrew J. Longmore and Susan B. Tritton. Using an 18-inch
Dob, Jay McNeil (of McNeil Nebula fame) made one of the
earliest documented visual observations - perhaps the very
ﬁrst with an amateur-size instrument - at the 1999 Texas
Star Party. LoTr 5 is located in Coma Berenices 6.8° east of
Collinder 256, the naked-eye open cluster that represents
Berenice's " hair. " The central star of LoTr 5 is the variable star

ζ
GEMINI

+20°

ν
J 900

γ
+15°

ORION

ξ
HR 2555

+10° HD 51104

K 2-2

Star magnitudes

located in Lynx about 2.5° northwest of the 4.8-magnitude
star 27 Lyncis. The planetary only becomes apparent when
viewed at low power through a nebula ﬁlter and appears as
a large faint disk. According to planetary nebula aﬁcionado
Kent Wallace, S&T Contributing Editor Steve Gottlieb and
fellow observer Jack Marling made the ﬁrst known visual
sightings of this object in 1985. But it was Prairie Astronomy
Club members David Knisely and Rick Johnson who bestowed
its nickname the Headphone Nebula.

HD 50005

MONOCEROS
7h 00m

6h 40m

3
4
5
6
7

6h 20m

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Sky & Telescope - March 2021

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