Framed, Captured, Processed and Researched by Steeve Body
Image acquired using Deep Space Remote Observatories – Australia equipment hosted by Swan Reach Imaging
Region overview
This 10-degree mosaic showcases a rich and complex area of the southern Milky Way, from the dark nebula SL 17 (The Dark Wolf) to the expansive supernova remnant RCW 114 (The Dragon’s Heart). It reveals extended filaments, shock fronts, and rarely imaged structures using deep narrowband imaging and full photometric continuum subtraction.
Highlights include:
• Newly revealed [O III] filaments connecting SL 17 to RCW 114, supporting a multi-shell or bipolar SNR interpretation.
• [S II] shock-excited knots across RCW 114, confirming its supernova remnant nature.
• A clearly defined WR 90 wind bubble interacting with the remnant interior.
• A potential new planetary nebula candidate, centred on a Gaia white dwarf.
• PHR J1702-4443, an elliptical planetary nebula with a compact [O III] core, only the second colour image ever published.
• A second PN-like structure near SL 17, centred on a YSO candidate, possibly misclassified.
• HaTr 5, formerly linked to Nova Sco 1437, now confirmed to be a faint, evolved planetary nebula.
Advanced Plate-solved image for reference
Annotated in light blue are HASH PN Database objects
What is new in this image
Most published images of SL 17 and RCW 114 on AstroBin and elsewhere are rendered in standard HOO or SHO palettes. In nearly all examples I’ve found, the images are either straight RGB, RGB+Hα, or very occasionally include [Hα], [S II], and [O III] filters, but without continuum subtraction. Only one other exception I located (from Capella Observatory South) performed such subtraction along with an analysis of the emissions lines and possible origin of the morphological structure of RCW114. However their image covered a narrower field (~6.5° across)
In contrast, this image published here covers 10 degrees and applies photometric continuum subtraction to every narrowband channel and maps [Hα] → red, [S II] → yellow, and [O III] → cyan. This processing reveals key features that are otherwise washed out or masked by contaminating starlight, broadband emission or hydrogen dominance:
1. Extended [O III] Filaments that runs between SL 17 and RCW 114.
Faint cyan filaments, most notably between SL 17 and RCW 114 appear to extend far beyond the “heart” structure of RCW114. These [O III] traces, not clearly visible in any previous amateur or professional image I have found, support the theory that RCW 114 may consist of multiple shock shells or bipolar lobes. The geometry also aligns with the pulsar PSR J1731–4744’s motion vector, reinforcing the idea of an evolving supernova remnant.
This mosaic extends the earlier Capella image significantly and captures western filaments that were hypothesised but never imaged. These filaments could indicate:
- A blowout zone in the remnant shell,
- A second ionisation front,
- Or an unrelated foreground interaction, possibly associated with SL 17.
2. Well-defined golden [S II] knots across RCW 114
These are usually masked by the dominant hydrogen emission. These knots help trace shock excited gas, supporting RCW 114’s classification as an evolved supernova remnant. (See: Welsh et al. 2003, A&A 403:605)
3. WR90 Bubble Clearly defined.
Clear differentiation between the [Hα] → red, [S II] → yellow, helps bringing out the bubble structure associated with WR90
4. Improved sulphur and oxygen filament detail around SL 17
The area around SL 17 benefits especially from continuum subtraction, which clarifies sulphur and oxygen contributions and better separates foreground dust from emission features. These details are not present in standard SHO/HOO renditions.
5. Potential New PN Candidate
We have a nebulous shell that appears elliptical with clear colour separation ([O III] + Hα).
- The centre has a white dwarf candidate identified in Gaia DR3.
- No planetary nebula is catalogued in SIMBAD, HASH, or MASH in this location.
- No nearby YSO, H II region, or active star formation markers in the field.
Simbad search
Identifier
Gaia DR3 5950996807204601088
Otype
WD? (White Dwarf Candidate)
Coords
17:20:13.27 −47:32:06.83
6.Planetary nebula PHR J1702-4443 (PNG 342.0-01.7)
PNG 342.0-01.7 a composite of [NII] (red) Hα (green) and [OIII] (blue) (Ali et al.: The planetary nebula PN G342.0-01.7)
Also visible in this field is PN G342.0‑01.7 , a confirmed planetary nebula from the MASH I survey. To my knowledge, beside the image taken as part of this research paper, this is the second colour image ever taken of this object. PN G342.0‑01.7 was discovered in the Macquarie/AAO/Strasbourg Hα survey (MASH I) and designated PHR J1702‑4443. It is classified as an elliptical planetary nebula with an angular size of ~90″ × 63″ and shows a one‑sided enhancement or ear‑like ring no colour image of this object has been published to date. This mosaic shows, for the first time:
- A compact teal [O III] core
- A faint red [Hα] outer shell matching the expected structure of evolved elliptical planetary nebulae.
- SIMBAD entry: PHR J1702-4443
- Research Paper: Ali et al.: The planetary nebula PN G342.0-01.7
- Flux reference: Frew, Bojičić & Parker (2012): arXiv:1211.2505
7. PN shaped region near SL 17 (centre coord 17 01 4.458 -42 35 51.6 (ICRS, J2000, 2000.0)
At first glance, the object appears to be:
- Roughly elliptical in shape, with a well-defined rim of ionised gas (red, likely Hα) and bluish inner glow (suggesting [O III]).
- There appears to be a potential central star, slightly offset, surrounded by a faint shell, classic planetary nebula traits.
- It’s not in HASH or MASH catalogues. No known white dwarfs.
- The SPICY 46289 object is a good candidate for a misclassified central star of a planetary nebula.
Main candidates of interest:
SPICY 46289
• Otype: Y*?
• Distance: 20.6 arcsec from centre, the closest stellar object that could plausibly be the central star.
8. HaTr 5 also know as PK 343-00.1 (not a Nova, Just a Planetary Nebula)
HaTr 5 is another really interesting object in this object wroth researching.
This faint nebula, known as HaTr 5, was once thought to be the leftover shell from a star that exploded in 1437. It was also believed to be linked to a nearby binary star system. But new research shows that’s not the case.
The nebula is too large, too slow, and contains too much gas to be from a nova. Instead, it’s now confirmed to be a very old planetary nebula, the glowing shell of gas left behind when a dying star like our Sun sheds its outer layers. The star system once thought to be responsible is just in the same part of the sky by coincidence.
You can read the full 2024 study here: https://arxiv.org/html/2412.12813v1
About SL 17 (Dark Wolf / Fenrir Nebula)
SL 17 (also catalogued as Sandqvist & Lindroos 17) is part of the star-forming Gum 55 complex in Scorpius and is located at a distance of around 5,300 light years away. The nebula appears to be a region of ongoing star formation. The dust absorbs visible light, making the region look dark, but in this cold dense material is where baby stars form. In such clouds, infrared radiation removes thermal energy and gravity can overcome internal pressure, causing clumps to collapse into protostars (Source).
Even thought there are a few images of this region on AstroBin, it is fairly under imaged target. Only just recently did the ESO captured in a 283-million-pixel image by the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile of this region. You can find the image here
About RCW 114 (Dragon’s Heart)
RCW 114 is a large and complex emission structure, either an old supernova remnant or a stellar-wind bubble around WR 90. Early imagery ([Hα]+[N II]) suggested it was an SNR, later spectral analysis confirmed this through global expansion and shock-excited [S II]/Hα line ratios.
The distance to RCW 114 remains debated. Early estimates placed it <200 pc away, but Welsh et al. (2003) argue for >1 kpc, likely 1.55 kpc (~5,000 ly), matching WR 90’s distance. In this picture, RCW 114 becomes the remnant shell of a long-dead progenitor, with WR 90’s wind expanding into its interior.
Crucially, this new rendition of this field posted here supports recent theories that RCW 114 consists of more than a single cavity:
- The newly revealed [O III] arcs to the west and north of the main “heart” suggest a larger bipolar structure.
- The alignment of filaments with PSR J1731–4744’s trajectory strengthens the case for an SNR origin.
- The WR 90 bubble appears partially embedded within, not driving, the larger remnant, consistent with its secondary role in excitation.
Processing notes
- Continuum removed with NightPhoton Photometric Continuum Subtraction.
- Median subtraction applied to all narrowband masters ([Hα], [S II], [O III]).
- Final colour mapping: [Hα] → red, [S II] → yellow, [O III] → cyan, screened over RGB so the LRGB Milky Way dust lane remains visible.
- Star field retained deliberately, star sizes reduced only enough to keep the dense field readable.
