Sky & Telescope - December 2022 - 21

HFG 1: NICO GEISLER / FRANK IWASZKIEWICZ; HUBBLE 12: NASA / ESA /
ACKNOWLEDGEMENT: JOSH BARRINGTON; ABELL 82: JERRY MACON
Her celestial majesty holds a pleasing selection
of planetary nebulae that you can enjoy all in
one winter's evening.
T
oward the end of the year, we find Cassiopeia, the
Seated Queen, high overhead shortly after sundown.
Under my rural skies the constellation's distinct W
blazes in front of a fairly bright section of the Milky Way. By
area, it's the 25th-largest constellation and adorned in copious
open star clusters. Which, as you might imagine, makes
it a great constellation for perusing with binoculars.
Recently, though, I was surprised to learn that Cassiopeia
also contains a wealth of planetary nebulae. The authoritative
Strasbourg-ESO Catalogue of Galactic Planetary Nebulae
lists 26 objects as " true or probable " planetaries in Cassiopeia.
I suspect that most observers pass them over because
the brighter ones are nearly stellar while the larger examples
are quite faint. In fact, only one of the 26 was actually discovered
visually!
Out West
On this tour, we'll visit Cassiopeia's 13 brightest planetary
nebulae, which I viewed using nothing larger than my vintage,
10-inch Schmidt-Cassegrain telescope. To make sure
you have time to get to them all comfortably, start in the
west and work your way east.
While our first target isn't the easiest to find, it compensates
by being the brightest. Known as Hubble 12, it's visible
in my 12×60 binoculars as a faint " star " 5.5° west-southwest
of Beta (β) Cassiopeiae (familiarly known as Caph) or about
3.5° south of the elegant open cluster M52. At 94× in my
10-inch, the nebula remains starlike, and a 12.3-magnitude
star lies 1′ east-northeast. In fact, even at 520× on steady
nights, the planetary remains stellar for me!
However, using his 18-inch at 807×, S&T Contributing
Editor Steve Gottlieb has seen a very small and faint 2″ halo
surrounding the 13.8-magnitude central star. So, without
enough magnification, I'm just seeing the faint central star
immersed in a tiny nebula, which is nearly two magnitudes
brighter. It was - you guessed it! - Edwin Hubble who discovered
Hubble 12 as well as four other planetary nebulae a
little more than a century ago. Today, we know it to be at an
early stage of evolution with a rare, nested bipolar hourglass
structure. Interactions between the two components of a presumed
binary central star may be instrumental in sculpting
its intriguing shape.
Next up is Abell 82, which lies 3.7° southwest of Beta
Cassiopeiae or 1.6° west-northwest of the rich open cluster
NGC 7789. American astronomer George Abell made
numerous discoveries during his prolific career, most notably
of galaxy clusters and planetary nebulae. We'll encounter
several of the latter here. He unearthed Abell 82 in his
examination of the National Geographic Society - Palomar
FARAWAY GEM Abell 82 is often likened to the well-known
Ring Nebula (M57) in Lyra due to its similar apparent extent, but
it's much fainter. Also, while the Ring Nebula lies at a distance
of around 2,500 light-years, Abell 82 is more than twice as far at
around 5,800 light-years.
sk yand tele scope .o r g * DECEMBER 2022 21
BILLOWING BUTTERFLY One of several planetary nebulae that
Edwin Hubble visually confirmed, Hubble 12 lies in western Cassiopeia.
It's a striking example of a bipolar nebula, i.e., it displays two
symmetrical lobes on either side of the central object, which in this
case is likely a binary star.
https://skyandtelescope.org/
Sky & Telescope - December 2022

Table of Contents for the Digital Edition of Sky & Telescope - December 2022
