New Discoveries: PN Candidates Ludgate 2/3, and the Circinus OIII Super-Bubble

I am pleased to present this deep SHO image of the Circinus Cloud revealing the new PN candidates Ludgate 2/3, the Circinus OIII Super-Bubble and possible new SNR filaments.

This is a special project for me, as most of the work was done by my son! My son also has a keen interest in astronomy, and asked if he could use my setup for his high-school science fair project. His project aimed to test a hypothesis that some planetary nebula have been missed in areas with bright background Ha emission and to demonstrate the PN discovery process. He selected a field just to the west of our prior Hidden SNR image on the basis it was a likely location to find something new, had significant background Ha emission, and was at a good altitude prior to the fair. With a little mentorship, he setup Voyager for the image capture and did all the image pre-processing -I will definitely have to keep him on for my future projects!

He did a great job creating the science images looking for new discoveries and found/registered 2 new PN Candidates -Ludgate 2 and 3!  The science fair was a great success, and his project was picked up for an article in our local newspaper and an interview on national radio. Now the science fair is finished, I have finally had a chance to work further on the images.

Circinus OIII Super-Bubble

Circinus OIII Super-Bubble

In the lower center of the image, there  is an area of prominent OIII emission, which has an interesting asymmetrical structure with a clear central region that is sculpted out of the background molecular clouds. The OIII emission surrounds a number of hot OB-type stars, and it appears that the stellar winds from these OB stars is forming an unusual wind blown super-bubble. I can not find any prior mention of this OIII emission bubble in the scientific literature, so if anyone has any other ideas as to the cause of this emission, please let me know.

Ha Bubble and Possible PN Candidate in the Circinus Molecular Cloud

Circinus Molecular Cloud

To the right of the image, you can see the prominent Circinus molecular cloud, which is an area of intense star formation. Within the dense molecular cloud, there is an interesting Ha bubble, which is located around the hot type B stars HD 134733 and TYC 9025-1436-1.  This appears to be uncatalogued but is visible on prior images. There is also a possible PN candidate at 15 15 48, -61 43 59 but this needs further supporting evidence to be registered.

Ludgate 2 (top row) and Ludgate 3(bottom row) PN candidates

Planetary Nebula

Scattering across the image are a total of 28 visible planetary nebula including the two PN candidate discoveries Ludgate 2 & 3. Revision D is an annotated starless image showing the locations of these 28 planetary nebula. Of the two new discoveries, Ludgate 2 is small stellar PN candidate visible in OIII and Ha emission. On DECaPS images there is a small green bubble structure evident.  Ludgate 3 is a spherical bubble like PN candidate visible in OIII emission, with the structure having characteristics typical of a PN. There is very weak Ha emission, and on DECaPS images a small central blue star is visible.

SNR in the lower left aspect of the image

Multiple SNR’s

At the bottom left of the image there is a chaotic region containing at least two SNRs. The most prominent object is RCW 89, which forms the North West aspect of SNR G320.4 -1.2. There is also a further SNR in this region, SNR G320.6 -1.6.  Further to the south, there is a prominent arc of Ha and SII emission, which has a high SII:Ha ratio suggesting the presence of shocked gas. This previously unreported filament may be an unrecognised aspect of SNR G320.6 -1.6 or SNR G320.4 -1.2.

Technical Details

Imaging Telescopes Or Lenses
Nikkor AF-S 400mm f/2.8E FL ED VR

Imaging Cameras

Chroma Filters

10Micron GM1000 HPS

Adobe Photoshop · Pleiades Astrophoto PixInsight · Starkeeper Voyager

Acquisition details

May 15, 2023 May 22, 2023 May 25, 2023 May 30, 2023 June 10, 2023 June 15, 2023


Integration: 51h 50′


Dunedin, NZ

Starless Image with Planetary Nebula Annotated including Ludgate 2 & 3

Follow me on Astrobin to stay up to date with my latest images.
Astrobin →

More Projects