Object of the Week, December 29, 2024 – Sharpless 2-264, the Lambda Orionis Ring

[Uwe Glahn]

Sharpless 2-264 (Lambda Orionis Ring, "Angelfish Nebula")
Constellation: Orion
Type: HII region (molecular cloud)
RA: 05h 35m
Dec: +09° 56’
Diameter: ~ 6°

Deep Sky challenges don't need telescopes at all and it all begins with our naked eye and simple binoculars. Don't motivated to bring out the telescope in the winter cold - today's OOTW is the right solution for that.

The history begins with a question. Was it possible to see the nebula with the naked eye in times without any light pollution but a very accurate observation of the night sky? In this case the meaning of Orion's head became a new dimension.
Finally, Steward Sharpless includes the large nebula in his second and final vision in 1959 by scanning the Palomar Sky Surveys.

From the physically aspect, Sh 2-264 belongs to the Orion molecular cloud complex (OMCC). It is connected to the more famous Orion Nebula and the large arc of Barnard's Loop. Lambda Orionis and its eleven B-stars of the young cluster Collinder 69 (the head of Orion) are responsible for the ionization of the surrounding material. The cloud is around 1100 light-years away. The shock front of an early supernova, one million years ago, drift the nebula apart. The more prominent north-western edge is shaped by dark nebulae, particularly by Barnard 30. Simbad listed the object also as "lam Ori Molecular Ring". Looking to infrared images [WISE], a ring structure is actually visible

But how about to see the often photographed angelfish visually?
Starting with the naked eye, under rural skies I could not spot it without filters. UHC brings out a faint but clearly visible glow around lam Ori. The glow seems smaller than expected. Barnard's Loop is easier to see. Switching to Hß filters, the glow around Col 69 is prominent and not much more difficult than Barnard's Loop. I would guess the size to around 4°-5° size. Smaller than the nebula is for real, perhaps because of the missing of the fainter eastern size?
Best instrument could be the new opera glasses, equipped with nebula filters in the front, but I have not experience with those instruments.
A normal binocular or small telescopes needs at least around 2° degrees field to sweep the brighter edges. To frame the whole nebula, the glasses needs around 8° field. My Nikon 8x30 with its 9° field was nearly perfect. Equipped with front filters (Hß), the whole nebular was visible in the field. An outstanding view.
But now it is your turn. What are your experiences, used telescopes and results?

image: Rainer Mannoff (200mm f/3.6; Canon 6Da, IDAS NB12)
SH2-264_Angelfish_2023.jpg

sketch: Uwe Glahn (8x30 binocular, Hß filters)
Sh2-264.jpg

As always - Give it a go and let us know! And may the New Year bring you lots of health and of course clear skies.

[wvreeven]

Very nice choice, Uwe! I have tried to observe some of these large emission nebulae from dark locations in Chile. On March 17, 2023, I tried the Lambda Orionis Ring with my 20" from the Rio Hurtado valley a few km south of the mountain tops hosting Rubin Observatory and Gemini South. My notes don't say if I tried naked eye and I am sure I didn't bring binoculars. Anyway, my notes read:

"With 31 mm and UHC some broad arc visible near Bellatrix. Nothing else. Too low in the sky?"

I remember that I saw it between the star Lambda Orionis and Bellatrix. Certainly worth a revisit.

[Clear Skies]

This region - a term I have come to use for, well, regions that are too large to simply call a group of nebulae - was first cataloged in 1951 by Georges Courtès as nr. 128 on his list. Gaze & Shajn included it in their third paper (1952, 71st entry) as Simeis 153 and again their fifth and final paper (1955, 64th entry). It was not until 1959 when Sharpless included in his second paper.

DSF OotW 2024-52 - Courtes 128 Ori.jpeg

Here it is in pdf.

Several nebulae that are part of this region were, individually, cataloged at earlier dates. There is quite a lot going on here.

The northernmost part was one of the first surveyed by Struve & Elvey, chalked up in 1938 as McDonald 4. In 1950 by Courtés as his nr. 121. Two years later Sharpless & Osterbrock added it to their list as nr. 4 and a year after that Gaze & Shajn tagged it as Simeis 139. Part of it was cataloged as nr. 41 on his list by Strohmeier in 1950, 3 years before Gaze & Shajn cataloged it as Simeis 140. But that's not all: on the southern edge of this part is a reflection nebula that goes by Barnard 122; Cederblad added it to his monumental work in 1946, as nr. 51. Gaze & Shajn listed is a the 52nd entry in their third paper, Herbig added is as his nr. 4 in 1960, it made it to Bernes' list as nr. 89, it's the 25th entry by Rojkovskij & Kuchakov and nr. 29 on Parsamian & Petrosyan's list.

South of McDonald 4 are nebula that form the westernmost part of the region. It's there we find Simeis 136, Simeis 137 and Strohmeier 42: together these 3 form Courtés 120.

Centrally are the open cluster Collinder 69 and nebula Cederblad 54, the "Lambda Orionis Cluster & Nebula", respectively.

The east-northeastern part goes by Simeis 154. South-southeast thereof is a smaller part that is Simeis 304, involving dark nebula Barnard 35 and the well-known "FU Orionis Nebula" (McDonald 64).

I remember that I saw it between the star Lambda Orionis and Bellatrix.

That would have been Simeis 136: the southwestern part of Courtés 120.

[j.gardavsky]

The Lambda Orionis Nebula Sh2-264

is my typical glactic DSO for the X.mas Season, and otherwise an indicator for the transparency of the night skies. Seen the last time with unaided eyes and through the binoculars on Dec. 25th, and 26th, 2024.

An older documentary sketch, showing this nebula together with the Barnard's Loop, is https://www.cloudynights.com/gallery...-2021-phase-i/

gallery_316833_14415_14227.jpg

The only filamentary structure, my eyes have resolved beyond doubt, is the Gaze Shajn filament [GS 55]63.

The photographic survey of the nebula is here, http://www.simg.de/nebulae3/ori-06.html

Wishing you a happy and prosperous New Year 2025,
Jiri

[j.gardavsky]

Hello Victor,

and thank you very much for the dissection of the Lambda Orionis Nebula in your post #3,

Jiri

[akarsh]

I looked at the lambda Orionis nebulosity last winter from Death Valley using my 18" telescope. I had a 31mm Nagler on it, which gives about 7mm exit pupil and was using an H-Beta filter. I just marked several random patches of nebulosity (not exhaustive) that I sensed in my logbook as seen below:

lambda_Ori.jpg.jpeg

[Clear Skies]

@ Jiri: Thanks!

@ Akarsh: What you marked with a question mark, suspecting Sharpless 2-263 is indeed correct, albeit that the nebula's primary ('historically first') designation is Cederblad 44, a.ka. the "Strawberry Nebula". It's appearance in blue and red light differs greatly, which explains why the southwestern part carries the designation Barnard 223.