Object of the Week September 24, 2023 – The Heart and Soul Complex

Heart Nebula, IC 1805, Running Dog Nebula, Sharpless 2-190
Constellation: Cassiopeia
Type: Emission Nebula
RA: 02h 33m 22s
Dec: +61°26’36”
Mag: 6.5
Size: 150' x 150'

Soul Nebula, Westerhout 5, Embryo Nebula, Sharpless 2-199, LBN 667, IC 1848 (open cluster)
Constellation: Cassiopeia
Type: Emission Nebula, Open Cluster
RA: 02h 55m 24s
Dec: +60°24’36”
Mag: 6.5
Size: 150' x 75'

Stein 368
Constellation: Cassiopeia
Type: Double Star
RA: 02h 32m 49s
Dec: +61°27’00”
Mag: 8.0, 10.1
Size: 10”

The constellation Cassiopeia is home to a large number of open clusters. There are over two dozen open clusters that are readily visible in amateur telescopes. At least another fifty open clusters have been identified in the constellation photographically. Our Object of the Week consists of a complex of multiple emission nebulae and open clusters. This complex region is a beautiful and photogenic and therefore is a frequent target of astrophotographers. Sadly much of the nebulosity and beauty of this region is not visible in amateur telescopes. As a result these objects are often ignored by visual astronomers. The challenge I present to you is to get out under the darkest skies you’re able, sprinkling in at least average transparency if not better, and begin your hunt for The Heart and Soul Nebulae.

The Heart Nebula (IC 1805) is an emission nebula located at an approximate distance of 7,500 light years. It is also known as Sharpless 2-190 (Sh2-190) or the Running Dog Nebula because, when seen through a telescope, it looks a bit like a running dog. The nebula has a magnitude of 6.5. It is 150 arcminutes in size and known for its intensely red glowing gas and dark dust lanes forming a shape that resembles a heart symbol.

The Heart Nebula forms this complex with its smaller neighbor Westerhout 5, more commonly known as the Soul Nebula. The Heart and Soul Nebulae complex spans an area about 300 light years across and is a vast star-forming region illuminated by the light of the young stars surrounded by star-forming clouds of dust and gas. The two large clouds are separated by only 2.5 degrees and physically connected by a bridge of gas. The stars in the region are less than a few million years old and are only beginning their life. For comparison, our Sun has been around for almost 5 billion years.

Both nebulae shine bright in red light due to the emission of that specific color of light by the excited nearby hydrogen gas. The nebulae form a large star-forming complex in the Perseus Arm of the Milky Way. The clusters found in the region belong to the Cas OB6 association.

The brightest part of the Heart Nebula has the designation NGC 896 in the New General Catalogue. It is classified separately because it was the first part of IC 1805 to be discovered.

The nebula’s glow comes from the radiation of a small open cluster of stars known as Melotte 15. The cluster contains very young, blue, hot supergiant stars about 1.5 million years old. It is located near the nebula’s center and home to several bright stars with a mass almost 50 times that of the Sun, as well as many faint stars far less massive than the Sun.

The Heart and Soul region contains a total of seven open clusters of young stars. Two of these, IC 1805 and IC 1848, are directly associated with the nebulae and share the catalogue designations with them. The others are Basel 10, occupying only 2 arcminutes of the sky, NGC 957 (10 arcminutes), and Berkeley 65 (5 arcminutes). Rounding off the group is the famous Double Cluster (the Sword Handle) in Perseus, formed by two bright, large open clusters known as h and Chi Persei or NGC 869 and NGC 884. The Heart Nebula lies only 5 degrees to the northwest of the Double Cluster.

Attachment 5231

The Heart Nebula lies in the vicinity of Maffei 1 (PGC 9892) and Maffei 2 (UGCA 39), the brightest galaxies in the IC 342/Maffei Group, the nearest galaxy group to our Local Group. The galaxies are difficult to find and observe as they are obscured by the Milky Way’s dust and stars, and their features are not easy to make out. Both galaxies – the elliptical Maffei 1 and the intermediate spiral Maffei 2 – were discovered in 1967 by the Italian astronomer and infrared astronomy pioneer Paolo Maffei, who detected the galaxies via their infrared emissions. Each galaxy contains billions of stars. At an approximate distance of 10 million light years, they are relatively close to the Milky Way compared to most known galaxies.

The central star of the Heart Nebula is the double star Stein 368 which shows a faint companion 10” to the east.

The Soul Nebula (Westerhout 5) is also an emission nebula. It is also known as the Embryo Nebula or IC 1848, which is a designation used for the open star cluster embedded within the nebula.

Westerhout 5 is about 100 light years across and has an estimated age of 1 million years. It contains several small open stars clusters. IC 1848 is embedded in the body of the nebula, while the clusters CR 34, 632 and 634 can be seen in the head. Small emission nebulae IC 1871, 670 and 669 are located just next to the Soul Nebula.

The nebula is being carved out by the stellar winds from the stars embedded within it, a process that leaves behind large pillars of material pointing inwards. These pillars are very dense and have stars forming at their tips. Each pillar spans about 10 light years.

Here are a two observing reports from Christian B. Luginbuhl and Brian A. Skiff taken from their book Observing Handbook and Catalogue of Deep-Sky Objects.
IC 1805
diam. 22' V = 6.5 Stars 62
This cluster is involved with an extended faint nebulo-sity. At low power, 6 cm will show a conspicuous clustering of about 25 stars embedded in a very faint haze. 25 cm shows a loose aggregation of about ten brighter stars and as many fainter ones in a 20' area, but no nebulosity is visible. In 30 cm, the bright mag. 8.5-9 stars are scattered in a 25' area. Near the center, grouped about a mag. 8 star, are 25 stars within 5' diameter.

IC 1848
diam. 12' V = 6.5 Stars 74 dimen. 40’ x 10”
This cluster is more definitely associated with nebulosity than oc-gn IC 1805, cf., in 6 cm. The stars are also fainter, less concentrated toward the center, and strung out to the E and W. No nebulosity is visible with 25 cm, but 65 stars, mostly mag. 11, can be seen in a 30' area. On the E side of the 8' core is a mag. 7 star. 30 cm shows the cluster stars grouped around the mag. 7 star and a mag. 8 star 2' SSE. The fainter star is surrounded by 12 stars in a 2' area with strings extending to the NE and SW. The brighter star is accompanied by eight stars in a l' area. Some nebulosity is visible around the bright stars.

Now it is your turn. Give it a go and let us know.

Attachment 5230
The Heart and Soul nebulae are seen in this infrared mosaic from NASA’s Wide-field Infrared Survey Explorer, or WISE. Also visible near the bottom of this image are two galaxies, Maffei 1 and Maffei 2. Maffei 1 is the bluish elliptical object and Maffei 2 is the spiral galaxy. All four infra-red detectors aboard WISE were used to make this image. Colour is representational: blue and cyan represent infra-red light at wavelengths of 3.4 and 4.6 microns, which is dominated by light from stars. Green and red represent light at 12 and 22 microns, which is mostly light from warm dust. Image: NASA/JPL-Caltech/UCLA

Here are two observations:

18": I only took a fairly quick look at this huge HII region ("Soul Nebula" or "Baby Nebula") at the end of the evening after a long examination of IC 1805 ("Heart Nebula"). In comparison, portions of this object clearly have a higher surface brightness using an OIII filter at 73x. Near the center is an E-W elongated, scattered group of stars (Cr 32), ~10'x4' in size. On the west end are two mag 7.3/8.3 stars (2' pair of O-class stars: HD 17505 (the primary ionization source) and HD 17520) with a number of fainter stars huddled nearby. About 60' to the ENE is another larger, scattered group (Cr 34). Weak nebulosity is evident throughout the field without a filter.

Adding an OIII filter greatly increases the contrast and nebulosity is fairly prominent in several different sections. About 20' E of Cr 32 is a brighter, elongated patch. To the east of this patch is a dark lane or intrusion and on the eastern side is a brighter, 10' circular glow (IC 1871) with an irregular outline. IC 1871 is located roughly 45' ENE of Cr 32. This patch is irregular in surface brightness with brighter streaks. A larger region spreads out to the east of the cluster increasing the total length to over 1.5 degrees. I also noticed brighter regions of nebulosity to the west of Cr 32, but didn't take notes on this area or try to follow the entire outline of the complex.


17.5": at 100x, the large but weak grouping Cr 32 is dominated by a 2' pair of mag 7/8 stars. They are both surrounded by several close, faint companions. The surrounding 1° field is undistinguished but appears weakly concentrated around the bright pair. Faint nebulosity is visible in portions of the field. At 220x, the view is striking with ~12 stars huddled around the southern mag 9 star including a nice pair of mag 12 stars nearly collinear and equally spaced. The brighter mag 7 star (STF 306) is surrounded by 8-10 companions. The 20' field is fairly rich but scattered with a matched pair of mag 9 stars ~10' N.

Using a UHC filter at 100x, the field is immersed in a very large, faint nebulosity about a degree in length, elongated E-W. A large, bright region elongated N-S is at the east end, ~35' following the core, and seems detached from the main cloud. It surrounds a weak scattered group (Cr 34) that is devoid of stars in the center. The main body of nebulosity has a sharper border and is generally brighter to the north of the core and fades into the background on the south side. The outline is interesting on the north side with irregular extensions and bulges. A small brighter circular patch stands out at the west end (about 10' W of the core).

I can contribute two sketches of these large, difficult but nice emission nebulas.

sketch IC 1805: 20x125 binocular, broadband nebula filter, NELM 6m0+
Attachment 5232
home

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sketch IC 1848: 4" binocular telescope, 23x, [OIII], NELM 6m5+
Attachment 5233
home

To complete the complex, here's an observation of IC 1805 with my 18":

IC 1805, dubbed the "Heart Nebula", is a cluster (Cr 26 = Melotte 15) involved with a huge emission complex (LBN 654) . The central cluster Mel 15 was striking at 73x, consisting of a 20' scattered group of mag 8 and fainter stars (I estimated 17 stars mag 8-10.5). Embedded within the group is a smaller, fairly rich, 4'x2.5' oval ring with over three dozen stars. Most of the stars are located along the irregular ring, itself, and not in the interior. On the SW side is the brightest member mag 8 HD 15558, an O5-type giant, which has a mag 10.5 companion at 10" separation (ADS 1920). The central region is richest around this pair with 9 or 10 stars in total packed into a 1.6' region.

Adding an OIII filter, the cluster was encased in a fairly bright, irregular glow, ~12-15' in diameter and extending mostly to the east of the cluster. There appears to be dark lanes or obscuring dust involved as the surface brightness is irregular with brighter filaments within the glow. Fainter nebulosity extends to the east and then abruptly bifurcates into two branches, one heading NE and the other SE. There's a sharp border to the nebulosity at the split as the sky directly east immediately darkens, adding to the contrast.

Following the stream of nebulosity to the NE, it extends roughly 20' in that direction but then curves back sharply towards the west where it meanders for 30'-40', ending about 30' N of the cluster. Only 20' E of the bend at the NE corner is the fairly large open cluster, NGC 1027 (see notes) .

The southern river of nebulosity can be followed around in a huge loop. First it gently curves to the south or SSE for ~40' and then loops back sharply towards the west (this band forms the southern boundary of the "Heart") for at least 40', heading towards a distinctive N-S string of 5 stars with a length of 6'. This group is catalogued as Markarian 6 = Stock 7. At the south end of Mrk 6 are two doubles, STF 264 = 8.6/9.8 at 17" and STF 263 = 10/11 pair at 17".

At this point, the rim bends to the north and brightens noticeably in a 10' patch. It dims and continues on further to the north, passing about 25' W of the cluster and fades out pretty close to NGC 896, a nearly isolated bright patch to the NW of the main structure. Near the northwest end of IC 1805 is Tombaugh 4, a low surface brightness cluster that requires high power to partially resolve.

I had now traced around the entire outline of the "Heart Nebula" visible on wide-field images, scanning over a degree and a half from north to south and perhaps 1.25° in extent from west to east. The entire outline, including the weaker interior glow, was also visible at 12.5x in my 80mm finder using an OIII filter, although without the detail visible in the main scope.

NGC 896 and IC 1795 are parts of a fairly bright, detailed region at the NW corner of this huge ring. The complex appears split into three or 4 distinct sections by dust lanes (LDN 1359). The largest section is IC 1795, which extends mostly north of a mag 10 star for ~8'. To the west of the mag 10 star is a dust lane oriented NW-SE and beyond this lane to the west is a small, moderately high surface brightness glow (NGC 896) of 2' diameter. To the east of the star is another broad dust lane extending N-S and east of this lane is a fainter wash of nebulosity that streams to the north for over 15' in length. It passes through mag 9 SAO 12287 and just north of this star the nebulosity has another small, brighter patch. Initially, I thought the complex ended here on the NE side, but additional fainter nebulosity was noticed spreading out to the west, increasing the total size to 15'-20' for both N-S and E-W directions.

Comparing my descriptions to the MegaStar outline, I noticed that the cluster Mrk 6 (perhaps it's an asterism) is not plotted, although the brighter stars are, of course. Secondly, the outline shows a large gap between the NW end of the Heart and NGC 896. Visually, it appeared the Heart Nebula extended closer to 896. Finally, I picked up additional nebulosity to the north of NGC 896 not shown on MegaStar. At the section of the rim ~25' W of Mel 15 is the "bright-rimmed cloud" BRC 5, which was not noticed visually, though contains many T Tauri candidates.

I've traced out the heart twice and the soul once. Both are challenging nebulae for visual observers. Here are some of my meager notes on some aspects of the heart nebula:

IC 1795 = NGC 896: "Easy and bright knot, kinda reminiscent of a galaxy, embedded in a nebulous background."
IC 1805: "A cluster embedded in a filamentous, nebulous background."
The most prominent structure I picked up in the heart nebula was the junction of the right atrium and right ventricle, which I described as resembling a "bird with open wings".

Attachment 5236

There is a LOT going on in this region. As I had just forayed into Cassiopeia to compile nebula guides, I had not yet reached this region of the constellation. But I put a rush on it and here it is using data from a variety of historical catalogs.

Attachment 5237 Attachment 5238 Attachment 5239

IC1805… that's not all of the "Heart Nebula", it's just a part of it. Specifically, the open cluster that later received the designation Melotte 15. Along with the bright nebulosity directly to its east that was designated by Georges Courtès as nr. 111, who noted is as the most intense region outside or at the boundary of IC1805. The fainter nebulosity of IC1805 was described by Cederblad but he, too, noted the brightest parts that Courtès added to his catalog a few years later.

But if IC1805 is not all of "the Heart", then what is the designation for the complex as a whole? I say it's McDonald 27, as Struve & Elvey were the first to designate it in their slit-spectrography project. Even when they did not explicitly list the extent and the dimension of the complex. Later designations were Simeis 3, Courtès 112, Sharpless & Osterbrock 9, Sharpless 1-136 and at the end of that list, the commonly used designation of Sharpless 2-190.

Gaze & Shajn also included fainter nebulous regions outside of the Heart outline: Simeis 3B, C & D. Beverly Lynds cataloged Simeis 3B as her nr. 650 and added nebula Lynds 655 south of the middle and 656 on the southern edge.

Stuart Sharpless, in his first paper, took note of the large and faint nebulosity to the northwest, but took the easy way out in his second paper and simply noted all of the Heart and the surrounding nebulae: IC1805.

The faint, very large and extremely elongated nebula protruding from the northeastern part of the Heart - the dog's tail if you look at the bigger picture - is Simeis 4.

Attachment 5240 Attachment 5241

Northwest of the Heart is the "Fishhead Nebula", or the Dog's head if you will. The fainter nebulosity is IC1795, the brighter western part is NGC896. But there's more to that western part, as Gaze & Shajn designated the brightest portion of it Simeis 1. That part stood out to me when I observed it in October 2017, but so did the northernmost part of IC1795. The proper designation for this small irregular part can not be stated with certainty, but I suspect Cederblad 6B can stick. If not, there's also Lynds 646. But Sven Cederblad's note of "A thirteenth mag. star with ditto", referencing his note for Cederblad 6A (NGC896) "with a fan-shaped appendix", does look tempting.

14" SCT @ 168x/29'

17mm Nagler T4:
NGC896 is visible unfiltered, slightly elongated on the western side from SSW to NNE with a larger, fainter part east thereof. That elongated, brighter part is Simeis 1.

17mm Nagler T4, Lumicon UHC:
Using this filter especially the elongated western part (Simeis 1) of NGC896 is brighter and slightly flattened on the NW side on a line from SW to NE. To the ESE there is an interruption in the nebula running SSW to NNE. East thereof is a larger, north south elongated part with a mag. 10.5 star on the SSE side. North of the mag. 10.5 star are a mag. 12 (SE) and a mag. 13 (NW) star aligned SE to NW. There is fainter nebulosity to the SSW of the mag. 10.5 star.

East of the mag. 10.5 star an interruption in the nebula is visible, NE thereof is a faint piece of nebulosity, elongated SSE to NNW (almost north-south). When following this elongated part towards the north there is a mag. 10 star with two mag. 12 stars to its NNW, aligned SE to NW. North of these two mag. 12 stars a small, patchy area is visible (Cederblad 6B(?) / Lynds 646).

17mm Nagler T4, Lumicon OIII:
An effect comparable to the UHC filter but not as strong. Using this filter the southern part of NGC896 is not visible.

On to the Soul. What goes for the Heart also goes for the Soul: the IC designation (IC1848) is not for the complex as a whole, it's the western part. First designation for all of the nebula(e) is McDonald 29. Later Cederblad 9B, Courtès 113, Sharpless 2-199 and Lynds 672.

Attachment 5242 Attachment 5243 Attachment 5244

Lynds again designated several brighter parts on the outskirts of IC1848. But in fact, Gaze & Shajn beat her to it; even when they did not apply designations, their extensive catalog notes leave no doubt:

A large, oval-shaped nebula, bounded by a brighter, albeit continuous ring. Near its center is HDE 237015 9.0 OE5 and, a little towards the west, a group of stars: HD 17505 6.87 O7, 17520 8.5 B, HDE 237007 9.2 B, 237011 9.4, B and 237012 9.3 B. Continuous emission is low compared to hydrogen. Filaments: 2h47.5m +60°15' (02:55:18 +60°39'29" J2000.0, Lynds 673) about 15' long, having an arc shape greater than 120°, 2h41.0m +59°57' (02:48:41 +60°22'08" J2000.0, Lynds 667) about 15' long and 2h43.0m +59°47' (02:50:41 +60°11'56" J2000.0, Lynds 670) about 40' long with a very sinuous shape on the southwestern boundary of the nebula and two globules: 2h47.3m +60°17' (02:55:06 +60°41'31" J2000.0, Lynds 1806) and 2h47.6m +60°22' (02:55:25 +60°46'29" J2000.0).

They even noted the globule that is Lynds 1806.

Cederblad's note for the Soul complex are intriguing. He designated the nebulosity of IC1848 as nr. 9B in his book, but also added 9C for the small, bright nebula IC1871 directly east-northeast of IC1848 (IC1871 is often incorrectly attributed to Simeis 24, east of the Soul). 9D is the small nebula directly north of IC1871. Even when Cederblad made an obvious error in the R.A./Dec. for this little one, his description "about 5' north of +60°596" leaves no doubt.

The eastern part of the Soul ("the head") is Simeis 6. The stars within form the open cluster Collinder 33, the group on the east-northeastern edge Collinder 34. I find it notable that this part was not properly recognized until the 1950's… although Struve & Elvey did make reference of it: "Ha and [OII] 3727 are very strong over the entire length of the slit, but especially near its eastern limit" and so did Cederblad when describing IC1848: "The nebulosity may possibly extend to the clusters No 33 and No 34."

Sharpless again took the easy way out: IC1848.

Allright… this came from the heart. Now it’s time to put my soul into more of the queen's nebulae.

Hello all,

the Valentin's Heart Nebula Sh2-190 has been the "strange attractor" for my eyes, and especially during the past 11 years, with the 100plus observing sessions I have spent with this nebula.
The latest details, which have attracted my attention have been the continuation of the Simeis 4 towards 03h05m +67°, and another fainter band towards 02h30m +66°30'. These both bands, I have nicknamed as the "arteries", are connected with a bridge across LBN 652.
Observed on August 11th, 2021, Bortle 3 skies over Erlanger Oberland, binoculars 15x85 (BA8), filters H-beta 12nm Astronomik.

The "arteries" are known from the H-alpha skies surveys, like in the MDW
https://www.mdwskysurvey.org/recent-...a-950b241c4d71

Clear skies,
Jiri

Thanks for the inspirational OOTW, I felt compelled to take another few looks at this object. I'm pleased to report an excellent view of the Heart Nebula that I enjoyed through my 25x100 binoculars. The skies were exceptional at a 6000' elevation parking lot in the dark Bortle 1 zone near "Natural Bridges National Monument" in Utah, USA. I was pleasantly surprised to see the heart-shaped nebulosity in my binocular without much difficulty, unfiltered!

NGC 896 formed the first nebulous patch that was readily detected in the field. It was a nebulosity around a star that sported a detached brighter knot. A thick band of nebulosity came down from just off east of NGC 896 towards the cluster, and then branched into two branches of nebulosity -- the top (N) boundary of the heart and the right (W) boundary. The nebulosity going in towards the cluster IC 1805 was thick and brighter, and appeared V-shaped. With some more effort, the entire outline of the heart could be traced out. The most difficult segment was the part to the south. I made a very rough representative sketch of what I saw
Attachment 5270
This was on 16th October 2023, two days after the annular eclipse, on my drive back.