Object Of The Week July 21, 2019 - NGC 6309, the other Box Nebula

[wvreeven]

NGC 6309, Box Nebula, Exclamation Mark Nebula, PK 009+14.1, PGC 3517781

Planetary Nebula

Constellation: Ophiuchus

RA: 17 14 04.3
DEC: -12 54 37.9

Visual magnitude: 11.50
Dimensions: 0.427' x 0.299'

This is one of the two objects called the Box Nebula, the other being NGC 6445 which was OOTW before (http://www.deepskyforum.com/showthre...highlight=6445). However, NGC 6309 sometimes is referred to as the Exclamation Mark Nebula, which seems to be a more fitting name. Unfortunately the origins of both names are unknown to me though the Exclamation Mark name may originate from Stephen O'Meara's book The Secret Deep.

NGC 6309 was discovered visually in 1876 by Wilhelm Temple. He used the 11” (280 mm) refractor of the Observatorio Arcetri of Florence, Italy. The nebula is classified as a bipolar nebula because it contains two bright blobs which are offset asymmetrically around the central star. This Hubble image of the central part shows a dimmer bar running through the lower part of the nebula perpendicularly to the major axis of the nebula

ngc6309hst.jpg

This is also visible in this spectacular drawing created by Belgian amateur Tom Corstjens

image_103576.jpg

However, this SDSS/NOAO composite image shows that there is a bigger deal to this nebula

ngc6309overlay.jpg

As a matter of fact, the nebula takes the appearance of a spiral galaxy! Perhaps that explains the PGC designation?

My observations using my 20” dob on August 9, 2013, were done with a not very high magnification which probably made me miss some of the finer details. However, I did manage to see part of the outer shell of the nebula. It is unclear whether this is part of the “spiral structure” or not though:

Found during twilight. At 366x an elongated glow with a star at the north-west side. The nebula is north-west south-east oriented. The nebula appears shaped like the number 8 with the impression of a dark lane running through it. At lower magnifications the south-east side appears a bit brighter. The south end seems to be elongated. I can't say whether that is part of the nebula or perhaps a faint star. An OIII filter increases the brightness of the nebula but doesn't make the details clearer.


As always,

"Give it a go and let us know!
Good luck and great viewing!"

[Steve Gottlieb]

Here are a couple of my observations of NGC 6309. As with most high surface brightness planetaries, high power is usually the key for details --

17.5" (6/30/00): at 280x using a UHC filter, this bright but compact PN was elongated 2:1 in the direction of a 12th magnitude star at the NNW edge, with dimensions of ~25"x12". There is a large, bright lobe or condensation at the north end with a smaller, fainter knot at the SSE end. At moments the lobes appear completely "resolved" with a darker gap in the center. The view at 500x (unfiltered) was excellent! The fainter southern lobe appears elongated and slightly offset from the major axis of the PN. The lobes are bisected by a darker lane oriented SW-NE and oblique to the minor axis. The brighter knot at the north end has a mottled appearance and irregular shape.

24" (8/13/15): this very bright, bipolar, compact planetary was viewed at 375x and 500x. The two lobes are extended at least 3:2 NNW-SSE with an overall size of ~25"x16" and a pear shape. A bright, roundish lobe is on the NNW side and a 12th magnitude star is off this side in the direction of the major axis [22" from center]. The smaller lobe on the SSE end is slightly fainter and separated by a small darker gap near the center. A mag 15 star is just off the west edge [14" from center]. An extremely faint outer shell or extension was just visible bulging out on the east side perhaps 10", creating an asymmetric appearance.

[Raul Leon]

Hi here's my observation from 7/12/2007 with my 14.5 Starstructure Dob f/4.3 at 200x ; The Box nebula ngc 6309 is a planetary nebula in Ophiuchus ; magnitude:11.5 size: 19"x10" fairly bright and elongated. Brighter to the North, did not see central star. ngc 6309.jpg

[Bertrand Laville]

Hi All,

I observed the PN for the first time in 2015; I didn't know it, and, if I suspected the central star, I missed the almond shape and the extensions.
I reobserved it on last june, and with the help of a good seeing, I improved my original sketch.
Details here: http://www.deepsky-drawings.com/ngc-6309/dsdlang/fr

Clear skies
Bertrand
http://www.deepsky-drawings.com

NGC 6309 T635 BL 2015 05 19.jpg

NGC 6309 T635 BL 2019.jpg

[Howard B]

My best observation is from July 2005 with the 28-inch scope:

"An unusually shaped planetary nebula that seems to have at lest two lobes and maybe a third, smaller one on the opposite end from the bright field star. The whole shape looks rather like a hornet's nest. No obvious color, 654x."

NGC6309sketch.JPG

Jimi and I plan to re-observe this beauty at the Oregon Star Party next week and we'll do our best to see the extensions.

[Uwe Glahn]

Nice PN Wouter.

The knot structure is for real spectacular when the seeing allows magnifications beyond 600x.

27", 837x, no filter, NELM 6m5+, Seeing III
NGC6309.jpg

The loops or the spiral structure are the brightest part of a somewhat larger halo. With mid size EP and [OIII] the knots and the halo were no problem and steadily visible with averted vision. (halo project)

27", 293x, [OIII], NELM 7m0+, Seeing III
NGC6309_Halo.jpg

Rubio et al. [MNRAS 2014] shows this observed and sketched halo with narrowband images AND even two knots much further away than the main halo. This could be a challenge for Barbarella.

[wvreeven]

This could be a challenge for Barbarella.

Inspired by a certain sci-fi movie?

[Dragan]

Inspired by a certain sci-fi movie?

The one and only!

[Howard B]

Jimi and I observed this cool planetary at the OSP in July and were able to see one of the flier extensions, which looked rather like a spiral arm. It came and went with the seeing but we saw it about 50% of the time:

"Hey now - we can see one of the spiral flier arms curving around the faint star right next to the nebula. But only with the NPB filter, which is what my sketch represents. Nice detail in the main part of the planetary too! 408x, NPB filter, 21.71 SQM."

NGC6309_crop.JPG NGC6309_cropinvert.JPG