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Cosmic Challenge: Emission Nebula Simeis 57
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Cosmic Challenge: September 2019Emission Nebula Simeis 57
Phil Harrington
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Target |
Type |
RA |
DEC |
Constellation |
Magnitude |
Size |
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Simeis 57 |
Emission nebula |
20h 16.2m |
43° 41.2' |
Cygnus |
-- |
23'x4' |
Simeis 57 is one of the most intriguing emission nebulae in the late summer
sky, yet it is almost unknown to visual observers. Photographers,
however, know it as a pair of opposing arcs of reddish light, one extending to
the north, the other to the south, that appear to be spinning symmetrically
away from a common center. Its unusual appearance has led to its two
nicknames: the Propeller Nebula or the Garden Sprinkler Nebula.
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Above: Summer star map. Credit: Map adapted from Star Watch by Phil Harrington |
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Above: Finder chart for
this month's Cosmic Challenge. |
The entire complex was assigned Simeis 57 when it was discovered in the early
1950s by G.A Shajn and V.E. Hase at the Crimean Astrophysical Observatory at
Simeis, Russia. Their results were published in the observatory's Bulletin
of the Crimean Astrophysical Observatory (in Russian, Izvestiya Krymskoi
Astrofizicheskoi Observatorii), although they did not become widely known
outside of the Soviet Union at the time, probably due to the Cold War raging at
the time.
Later, portions of Simeis 57 were assigned separate designations in various
catalogs. The propeller's southern blade is listed as DWB 111, after a 1969 article detailing the Cygnus X region, written by H.
R. Dickel, H. Wendker, and J.H. Bieritz that appeared in the journal Astronomy
& Astrophysics (A&A, vol. 1, p. 270 - 280). The same article
listed the northern blade as DWB 119. Fainter sections were assigned
other DWB numbers, although for our purposes here, we will concentrate on
trying to see the propeller itself. That's tough enough. (Sidebar:
For a more up-to-date review of the physics behind Simeis 57, read The
peculiar nebula Simeis 57-I. Ionized gas and dust extinction, also
published in Astronomy and Astrophysics [A&A vol. 398, p.
1063-1071].)
As with so many emission nebulae (or hydrogen-II regions, if you prefer), the
Propeller Nebula is very difficult to see by eye alone. That's because
its primary emissions lie in the red portion of the visible spectrum, where our
eyes are all but blind under dim light conditions. And they don't come
much dimmer than Simeis 57.
The blades of the propeller span about 20', so in order to squeeze both into
the same view, select an eyepiece with a real-field coverage of at least half a
degree. A modern, ultra-wide design with an 80°-plus apparent field is
better than, say, a more conventional Plössl, since their wide apparent fields
also produce a higher magnification for the given real field. That's
important consideration, since higher magnification will generate better image
contrast.
To boost contrast further, experiment with various nebula filters. Not to
plant any preconceived prejudices in your mind, but narrowband (UHC-type) and
O-III filters seem to offer little positive effect on the Propeller. On
the other hand, a Hydrogen-Beta (Hβ) filter, which rarely seems to help
objects beyond the Horsehead Nebula, usually proves to be the top choice
here. But again, try each filter in your cadre and see which produces the
best results.
The Propeller is 5° southwest of Deneb [Alpha (α) Cygni], and just to the
west of a right triangle the 7th-magnitude stars SAO 49403, 49413, and
49418. While that triangle is obvious in the 8x50 finderscope attached to
my 18-inch, the Propeller itself takes better skies than I can hope for from my
suburban observatory. Under naked-eye limiting magnitude 6.5 skies,
however, the 18-inch at 94x and with an Hβ filter in place reveals a very
soft glow after a concentrated search.
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Above: Simeis 57 as seen through the author's 18-inch (46cm) reflector |
Of the two blades, the northern component, DWB 119, impresses me as slightly
more obvious. It lies just northwest of the triangle. My notes
recall the softest of glows, a gentle, concave arc opening toward the
west. Two close-set 12th-magnitude stars appear centered along the length
of the arc, while an 11th-magnitude star marks its northern tip.
The southern blade (DWB 111) is a tougher catch. Look for a close pair of
9th-magnitude stars just to its west; they make a handy reference marker in
much the same way as 52 Cygni does for the NGC 6960 segment of the Veil
Nebula. DWB 111 is a mirror image of DWB 119, with its curve opening to
the east, more or less toward the right triangle of stars.
Interested in hunting for more Simeis objects? CN'er ngc4565adam started
a thread in the Deep Sky forum some years back asking for a
source of the catalog. A pair of Steves (Saber and Gottlieb) posted
replies. The former Steve (Saber) shared a link to SIMBAD that gives 231 entries, while the latter
(Gottlieb) offered a second link listing some pertinent Simeis publications.
The thread and links are all worth visiting.
Until next month, remember that half of the fun is the thrill of the
chase. Game on!
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About the Author: |
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Phil Harrington's Cosmic Challenge is copyright 2019 by Philip S. Harrington. All rights reserved. No reproduction, in whole or in part, beyond single copies for use by an individual, is permitted without written permission of the copyright holder. |
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- Dave Mitsky, okiestarman56, John O'Hara and 2 others like this
6 Comments
I don't own a scope in this size class, but I have buddies who do that will be coming to the Black Forest Star Party later this month. More to come!
"a Hydrogen-Beta (Hβ) filter, which rarely seems to help objects beyond the Horsehead Nebula,"??? Oh, Phil, where have you been? :-)
USEFUL TARGETS FOR THE H-BETA FILTER
While the H-Beta is probably one of the less-used nebula filters, the commonly expressed idea that it works only on a handful of objects is not necessarily true. Here is a list of *some* of the more prominent objects that the H-Beta may be at least somewhat useful on. Some may require larger apertures (and some may be slightly better in other filters), but a few have been seen from a dark sky site by just holding the filter up to the unaided eye and looking at the sky. Some of these will also be helped by a narrow-band filter like the Lumicon UHC.
1. IC 434 (HORSEHEAD NEBULA)
2. NGC 1499 (CALIFORNIA NEBULA, naked eye and RFT)
3. M43 (part of the Great Orion Nebula)
4. IC 5146 (COCOON NEBULA in Cygnus)
5. M20 (TRIFID NEBULA, main section)
6. NGC 2327 (diffuse nebula in Monoceros, part of the Seagull)
7. IC 405 (the FLAMING STAR NEBULA in Auriga)
8. IC 417 (diffuse Nebula in Auriga)
9. IC 1283 (diffuse Nebula in Sagittarius)
10. IC 1318 GAMMA CYGNI NEBULA (diffuse nebula in Cygnus)
11. IC 2177: SEAGULL NEBULA (Diffuse Nebula, Monoceros)
12. IC 5076 (diffuse nebula, Cygnus)
13. PK64+5.1 "CAMPBELL'S HYDROGEN STAR" Cygnus (PNG 64.7+5.0)
14. Sh2-157a (small round nebula inside larger Sh2-157, Cassiopeia)
15. Sh2-235 (diffuse nebula in Auriga).
16. Sh2-276 "BARNARD'S LOOP" (diffuse nebula in Orion, naked eye)
17. IC 2162 (diffuse nebula in northern Orion)
18 Sh2-254 (diffuse nebula in northern Orion near IC 2162)
19. Sh2-256-7 (diffuse nebula in northern Orion near IC 2162)
20. vdB93 (Gum-1) (diffuse nebula in Monoceros near IC 2177)
21. Lambda Orionis nebular complex (very large, naked-eye)
22. Sh2-273 "Cone" Nebula portion south of nebulous cluster NGC 2264
In addition, a number of the brighter nebulae like NGC 7000 or M42 will respond to H-Beta use for revealing certain specific detail, although other filters may provide a somewhat better view overall. Clear skies to you.
David,
Of the objects listed above, which, if any, would you consider H-Beta to be the best option? I've also long believed that the H-Beta was primarily for the California and Horsehead nebulae, and have never made the plunge to purchase one, despite being a deep-sky observer for 40 years. My scopes range in size from 2.4" to 12.5". Sound's like it's high time I take the plunge.
Thanks,
John
The California Nebula is certainly the most prominent with the H-Beta, as I have held it up to my eye and seen it using just the filter and no other optical aid. The Trifid's main section looks larger in the H-Beta than in almost any other filter, yet appears to be kind of weird looking with that filter, as it kills the nebulosity right around the central double star, as well as killing off the reflection nebulosity next door. The IC 1318 Gamma Cygni nebular complex also responds well to the H-Beta, although it is faint and you do need a richest-field instrument to really get much of it in the field of view. The "propeller" nebula is adjacent to the Gamma Cygni complex, so it isn't surprising that the H-Beta filter would help it most. Clear skies to you.
Dear Phil,
Thanks for recommending this challenge object as I thought under my Bortle 8 skies and modest equipment this object was certainly out of reach. But using my Orion ED80 with an Astronimik CCD CLS filter and ZWO ASI174mc cooled camera, this image is the result of a clear New Jersey night, 35 90sec. images stacked and only put through DSS.
Avid follower,
Daryl L.
I was wondering if this would be mentioned.