Bat-Cave in Centaurus

by Zaytsev and Hanson

Wonderful Description and Annotation By Alex Zaytsev

The HII region RCW 79 (GUM 48c, GRS G308.60 +00.60) [1, 2] embedded into a massive molecular complex of Centaurus has been studied extensively [3, 4], yet it remained a rarely imaged target which is often overlooked in favor of its neighboring RCW 78 (GUM 48b) HII region [5, 6]. Here we present a close-up look at RCW 79 with Chilescope Telescope #1 system that reveals a remarkably complex structure of the rim of this HII region, filled with lots of small dark nebulae, one of which resembles a certain character of popular fiction to such an extent that it prompted the choice of name for the scene [7, 8]. 

Fig. 1 and Fig. 2 point out the most notable features found in the rim of RCW 79. WIth distance to this HII region estimated as 5.3 ± 0.4 kpc [3, 4] the characteristic size of the HII region itself is only about 60 ly, the linear size of pillars 1 and 2 identified in FIg. 1 and Fig. 2 is about 1.3 ly, and the wingspan of the “Batman figurine” is about 13 ly.  An open cluster Cl VDBH 151 [9] with measured parallax of 0.176 ± 0.013 mas is likely physically sitting inside the inner volume of the HII region, as its distance estimate of 5.7 ± 0.4 kpc based on that parallax is consistent with the distance estimate to RCW 79.

Fig. 1. Custom annotated cropped version of the upper center part of the original image naming the most prominent features of the rim here, shown in 100% of original resolution.

Fig. 2. Custom annotated cropped version of the left center part of the original image naming the most prominent features of the rim here, shown in 100% of original resolution.

Another visually striking feature of this scene is the “dark stream” crossing the area from top left side to lower central side consisting of multiple dark clouds elongated in the direction of the “stream”. This creates an illusion of the inner volume of RCW 79 to be lit from some external source at the top left side.

The 4.5 mkm and 8 mkm IR imaging of this target by Spitzer [10-13] reveals more structures inside the rim of RCW 79, but most of the peculiar features listed above aren’t easily identifiable in IR images. Fig. 3 shows the Spitzer IRAC HEALPix survey color data [14] for the FOV of the image. As pointed in [9, 10] the RCW 79 remains an active star formation region with age estimated at 1.9 Myr [10, 11]. A compact (“only” about 9 ly across) HII region IRAS 13374-6130 [15] is emerging around one of those star formation sites, which is likely to open into the inner volume of the RCW 79 later during its evolution, resulting in a similar configuration as currently observed for Gum 48d - an older (about 4 Myr old) and less distant HII region in Cen [16, 17].

Overall, the RCW 79 turned out to be full of unexpected and visually striking features that deserve further study with large aperture systems.

Fig. 3. Annotated version of Spitzer IRAC HEALPix survey color data [14] overlay for the FOV of the original image scaled up to match the original image resolution.

Data and initial calibration/integration: Alexandr Zaytsev https://www.astrobin.com/users/m57ring

ASA Ritchey-Chretien RC-1000: D=1m, f/6.8 on alt-azimuthal direct drive fork mount, FLI ProLine 16803 with secondary mirror based motorized focusing and automatic de-rotation (Telescope #1 system of ChileScope observatory, Río Hurtado Valley, Chile).

9x Ha + 8x OIII + 8x SII guided 1800 sec exposures (12h 30min of combined integral) collected over 4 imaging sessions carried out on May 19, 23, 24, 28, 2025 using Chilescope Telescope #1 system.

Image Processing: Mark Hanson

Enjoy, Mark and Alex

[1] https://simbad.cds.unistra.fr/simbad/sim-id?Ident=rcw+79&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id
[2] http://galaxymap.org/cat/view/gum/48c 

[3] https://ui.adsabs.harvard.edu/abs/2002MNRAS.336..736C/abstract 

[4] https://articles.adsabs.harvard.edu/pdf/2002MNRAS.336..736C 

[5] https://simbad.cds.unistra.fr/simbad/sim-id?Ident=rcw+78&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id 

[6] http://galaxymap.org/cat/view/rcw/78 

[7] https://en.wikipedia.org/wiki/Batcave 

[8] https://static1.srcdn.com/wordpress/wp-content/uploads/The-Dark-Knight-Rises-Batcave.jpg 

[9] https://simbad.u-strasbg.fr/simbad/sim-id?Ident=Cl+VDBH++151&NbIdent=1

[10] https://ui.adsabs.harvard.edu/abs/2006A%26A...446..171Z/abstract 

[11] https://www.aanda.org/articles/aa/pdf/2006/04/aa3952-05.pdf 

[12] http://galaxymap.org/mwe/mwe.php?centreLon=308.6267291279909&centreLat=+0.5664142751285641&zoom=9&tile_set=mipsgal&show_markers=1 

[13] https://apod.nasa.gov/apod/ap070714.html 

[14] https://alasky.cds.unistra.fr/Spitzer/SpitzerI1I2I4color/ 

[15] https://simbad.u-strasbg.fr/simbad/sim-id?Ident=IRAS+13374-6130&NbIdent=1 

[16] https://simbad.u-strasbg.fr/simbad/sim-id?Ident=gum+48d&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id 

[17] https://www.astrobin.com/cfxmtd/