Object of the Week, July 21, 2024 - Knot Cataloged

[Clear Skies]

Now, I've never really thought of Cygnus as a summer constellation. Even when the constellation's Alpha star features prominently in the so-called "Summer Triangle" we all have read about ad nauseum (seriously: one more article featuring that term and I will scream).

Maybe it's because astronomical twilight is only now returning to my latitude and that always being a prime reason for me, personally, for little to no observing as of mid-May. Also, August is approaching fast, yet the Swan does not transit until well after midnight. It's that time of night, when objects are near their highest elevation, when I do the bulk of my observations. The less atmosphere to interfere with photons, the better. It's therefore that I consider the Swan to be a late summer constellation, at best. It favors the evening skies of September and remains positioned favorably well into October. True, September still counts as summer, but by then the leaves will be changing color quite soon, at least in the northern hemisphere.

Regardless, this ensures you have plenty of nights remaining in the months ahead to tackle this week's OotW. Which is a little knot of a nebula.

A little knot that is - to the best of my knowledge - uncataloged. That, however, does not mean it has not been recognized before. It has, but the only reference to it I have been able to find is a single entry in SIMBAD.

The other day I was doing some nebula work in Cygnus. There's a lot going on over there. Up to my armpits in Hubble, McDonald, Cederblad, Minkowski, Courtès, Gaze-Shajn, Simeis, Sharpless and Herbig nebulae, I reached a piece of sky that is west of the Pelican. West-southwest of that famous cloud is faint and elongated Courtès 70; you may until now have only known it as Lynds (LBN) 334. Don't worry: the veil on this catalog and the beforementioned ones will be lifted soon. Downloading imagery and scrolling through Aladin Lite, a bright little fella stood out amidst the many fainter nebulae of the region, half a degree north-northwest of the Courtès.

The position is 20:45:38 +44:15:00. This is what it looks like (all images 15', 1/4 of a degree):

DSS POSS2 Red

15red2.jpeg

DSS POSS2 Blue

15blue2.jpeg

SDSS

15SDSS.jpg

PanSTARRS

15panstarrs.jpg

2MASS

152mass.jpg

allWise

15allWISE.jpg

It's small. It's faint. It's irregular. Its center is ring-shaped. It's about 2.5' in size. In the middle, there's a mag. 14.7 star, on the north-northwestern edge is a mag. 10.5 one.

Nature of the object? I am going to go with emission nebula... but I am not sure. It does look a lot brighter in the red imagery than it does in the blue.

Designation? As said, there's only SIMBAD and that's where it goes by GAL 084.0+00.8. That page tells us there's also a radio source at that position, identified by Felix. J. Lockman: 83.941+00.781 on page 476 of this paper. Likely to be a match for 3C 423. At or near the position an IR star cluster was identified, too, but when it comes to nebulosity, I have been unable to obtain any more information. That is quite a surprise, as this is a piece of sky that has been photographed at least once or twice.

Is it in reach of moderately large amateur apertures? I cannot (yet) speak from experience, but I suspect 12 inches and a filter ought to do it under good skies.

Here's the observing guide that will help you to pinpoint it.

DSF OotW 2024-29 - GAL 084.0+00.8 Cyg_1.jpeg DSF OotW 2024-29 - GAL 084.0+00.8 Cyg_2.jpeg

Give it a go, be sure to report back, and if you have any further information on this knot: let us know..!

[carlomuccini]

Thanks a nice subject to shoot.

Thanks again

Carlo

[Steve Gottlieb]

Nice choice for OOTW! This nebula is also in Neckel and Vehrenberg's Atlas of Galactic Nebulae as GN 20.43.9 (though SIMBAD doesn't include the alias).

I haven't looked for it, but Sue French mentioned it in her September 2013 Deep Sky Wonders column and even reported a sighting in a 5.1-inch scope at 117x.

[Clear Skies]

Thanks Steve and Carlo! Also Steve for the GN designation. Using that for a Google search did produce some results. As I understand it, the GN 20.43.9 designation is only mentioned in a 1980's era book that exists only in print. Pity that information and designation is not readily available in this digital day and age. Also makes one wonder what other information it may contain. I hope it will be digitized and shared with the whole wide world sooner rather than later.

[ScottH]

Nice choice for OOTW! This nebula is also in Neckel and Vehrenberg's Atlas of Galactic Nebulae as GN 20.43.9 (though SIMBAD doesn't include the alias).

I haven't looked for it, but Sue French mentioned it in her September 2013 Deep Sky Wonders column and even reported a sighting in a 5.1-inch scope at 117x.

How the heck did you dig that up? Do you have a list of objects Sue has covered during all her years??

Scott

[Steve Gottlieb]

I don't have a complete index from her articles, but entered this object in my database of observed and 'planning to observe' DSOs at that time or perhaps earlier if I ran across it in a journal paper.

Here's what Sue wrote in Deep Sky Wonders:

Next we'll call on the little-known blob of emission nebulosity GN 20.43.9. The "GN" in this name indicates that the nebula is listed in the Atlas of Galactic Nebulae (Thorsten Neckel and Hans Vehrenberg), and 20h 43.9m is its right ascension for equinox 1950.0. The nebula sits 1.3° southeast of Deneb and 49' west-northwest of 5th-magnitude 56 Cygni. My 130-mm scope at 117x shows a 5'-tall kite of 10th- to 12th-magnitude stars flying north-northwest. A very faint drop of nebulosity dangles from the kite's brightest star, the one at its western corner. The drop is about 1 1/3' long, and a dim star lies just off its southeastern end.

GN 20.43.9 contains the young star cluster DBCL23, which is visible in narrowband infrared images. The cluster stars have blown out a cavity in the nebula, whose glowing walls now surround it.

In fact, there was a short thread on CloudyNights on July 31, 2013 with replies from David Knisely, Reiner Vogel and myself, but I don't believe anyone posted observations afterwards.

[carlomuccini]

VIXEN FL80S WT
Filter Ha Baader Planetarium
ZWO ASI 294MM
2x900s
22/07/2024 23:34 UT
WCO237 osservatorio
Montecatini Terme - Toscana - Italia

I also took a 15 minute photo with the Baader IRcut filter but the object is barely visible.


Carlo


[DSF OotW 2024-29] GAL 084.0+00.8 [Cyg].jpg

[Steve Gottlieb]

Thanks Steve and Carlo! Also Steve for the GN designation. Using that for a Google search did produce some results. As I understand it, the GN 20.43.9 designation is only mentioned in a 1980's era book that exists only in print. Pity that information and designation is not readily available in this digital day and age. Also makes one wonder what other information it may contain. I hope it will be digitized and shared with the whole wide world sooner rather than later.

The 3-volume atlas was available in digital format (PDF) on DVD at one time by the publisher. This thread on CloudyNights for 2022 has more information and links. Owen Brazell may have something to add on this.

As far as the designations, the reflection nebulae in the atlas are included (with Neckel/Vehrenberg designations) in Magakian's Merged Catalog of Reflection Nebulae and that is available on Vizier here.

[kisspeter]

Very interesting object! I'll hopefully be able to try it in August.

Jeff Kanipe devotes a couple of pages to this little nebula in the Annals of the Deep Sky vol. 8 from page 132: "Interlude: A Mystery Flea in the Sky".
Also, Guide 9 plots it as GN 20.43.9

[Clear Skies]

"the Flea"

That's a fitting nickname!