Object of the Week, August 10, 2014 – The Propeller Nebula, AKA Simeis 57 = DWB 111 =

[Paul Alsing]

Object of the Week, August 10, 2014 – The Propeller Nebula, AKA Simeis 57 = DWB 111 = MRSL 479

CYGNUS
RA: 20 16 17
Dec: +43 43 00

Type: PN Emission Nebula, HII region
Size: about 20' overall, brightest parts smaller
Mag: ~15V?

Before writing up my OOTW articles I always do a little research on the object or objects, in order to hopefully appear a little smarter than I really am. :D For years I thought this object was only known as DWB 111, or #111 on the 1969 193-object list of Dickel, Wendker, and Bieritz. I was therefore surprised to find out that a 2002 paper about this object, found here...

http://arxiv.org/pdf/astro-ph/0211428v1.pdf

... tells me that this object is more correctly called Simeis 57, and is comprised by no less than (3) DWB objects, as delineated in this photo, where several other DWB objects in the area are indicated as well...

1332

During this research I also found a reference for another designation, MRSL 479, the MRSL catalogue having been authored by a Czechoslovakian astronomer. It is a compilation catalogue of previously known objects.

I first learned of this object some years ago via a negative observing report someone posted back in 2004, and thought I would give it a try myself, using my 25" f/5 Obsession. I downloaded the DSS overlay in Megastar and stretched the image a little to show the extents of the nebulosity, and to have a good reference at the eyepiece. There are 2 brighter areas, these being the northeastern (DWB 119) and the southwestern (DWB 111). My newly-found labeled photo says that DWB 118 is also in there, but I never saw that. Observing with a mixture of eyepieces and filters, all I really saw were the 2 brighter previously mentioned sections, and only when using the H beta filter. DBW 119 and DWB 111 were initially perceived as parallel but offset bars. After many minutes of observing, I finally teased out the curves at the south end of DWB 119 and the north end of DWB 111, finally suggesting the "S" shape so prominent in photos. I was in the Anza-Borrego desert east of San Diego and the night was just average for seeing and transparency at this location.

There are a couple of pretty multiple stars in the vicinity. This chart I created shows their location, magnitudes and separations...

1333

Fox 252 is a nice wide double that have a one magnitude difference, and ADS 13611 has 6 components, ranging in magnitude between 8.4 and 13.5. I didn't see all 6, but I remember I thoroughly enjoyed trying to do so!

This is a very dim object, but I read that it has been glimpsed in apertures down to 10" by experienced observers. As always...

"GIVE IT A GO AND LET US KNOW"

[reiner]

Hi Paul,

this is a really nice pick as OotW!

I have observed the propeller several times, though not in the past years. My observations were with my 14 and 22" Dobs. The field can be easily identified due a distinct superimposed star pattern. The nebula responds well to H-beta filter, though it is too large to fit into the field with my instruments. I therefore had to sweep the field to see the entire nebula. Both northern and southern wing of the propeller were quite well visible.

The southern part could be observed farther out than the northern part, which is not obvious from images as it does not appear brighter. It is probably a superimposed dark cloud on the southern part, that allowed me to perceive some kind of contrast.

There is further filamentous nebulosity beyond the Propeller in the direction away from Gamma Cygni, that is evident from widefield imaging. I have tried to see these faint filaments several times, but they are considerable more difficult. I have no notes on these observations, but I think I was never successful in seeing these filaments definitely.

[Steve Gottlieb]

The Propeller Nebula is a pretty well known imaging target, but hardly known as a visual target. Perhaps others will give it a try now that its an OOTW!

Like Paul, I also found it enhanced with an H-beta filter. Here are my notes from several years back (using the designations mentioned by Paul)

18" (9/15/07): the Propeller Nebula was viewed at 73x using an H-beta filter. Although very faint, two sections of this elongated "S" shaped emission strip were visible. The most prominent section (DWB 119) is at the north end and consisted of a 5'x2' strip elongated N-S. Just north of this strip are mag 8.8 and 10.5 stars and the nebulosity extending south from these stars for roughly 5' in the direction of a bright isosceles right triangle of mag 7.5-8 stars (sides 4.5', 4.5' and 6') including the double star Fox 252 (8.9/10.4 at 19"). Two nearby mag 10 stars complete a pentagon. The middle section of the Propeller (to the west of the pentagon) was extremely weak or likely missing, but at the south end a smaller 3'x2' piece (DWB 111), elongated N-S, was faintly visible to the SSE of ∑2659 = 8.4/9.5 pair at 20".