Object of the Week January 1st, 2023 - NGC 7538 The Northern Lagoon

NGC 7538
SH2-158

Emission Nebula

Cepheus

RA: 23 13 42.0
DEC: +61 31 09

Mag:
Size: 9.7’ x 6.1’

Nicely positioned shortly after twilight is NGC 7538, a compact nebula located in Cepheus. Often overlooked by observers as they head on over to see the nearby Bubble Nebula (NGC7635), M52 or SH2-157, NGC7538 – also known as the ‘Northern Lagoon’ or ‘Little Lagoon Nebula’ is a moderately bright emission nebula that can be seen in a variety of telescope sizes and is definitely worthy of a visit.

Discovered using his 18.7” speculum mirror telescope in 1787, Sir William Herschel described NGC7538 as "pBM, 2 considerable stars involved in nebulosity, 2' long, 1.5' broad.". NGC 7538 is home to the largest protostar system ever discovered – NGC 7538S. NGC 7538S is a supermassive rotating disk surrounding what appears will become a high mass type O or B star. Measurements reveal the protoplanetary disk to be approximately ~30,000 AU across containing a protostar of ~40 million solar masses [1].

Visually, NGC 7538 makes for a fine view in all manners of aperture. Although a filter such as UHC or OIII is required, online reports reveal the nebula being seen in scopes as small as 6 inches. In larger apertures, the nebula will appear somewhat irregular and elongated NE to SW with a slightly darker center region, home to the 2 12^th magnitude stars Herschel noted. Filters tend to darken the inner region even further while revealing fainter tendrils of nebulosity extending beyond the body of the nebula.

NGC 7538 makes for a fine object, particularly since it sits amongst some true eye candy. I’d almost make a bet that although most observers have seen the Bubble Nebula or M52, a fraction of those have made a visit to this underestimated treat only a few degrees away.

So the next time you get out, please make yourself a note to add NGC7538 to your observing list. And as always,

“Give it a go and let us know!”

Attachment 4990
©Fred Calvert/Adam Block/NOAO/AURA/NSF


[1] https://iopscience.iop.org/article/10.1086/376612/pdf

Hi here's my observation from 10/17/2009 : ngc 7538 nebula in Cepheus : mag:? ; size: 9'x6' ; fairly bright nebula, with OIII filter shows better contrast, noticed about 3 stars embedded in the nebulosity. I used a 10mm Radian at 198x with my 14.5 Starstructure f/4.3Attachment 4991

Nice choice Dragan! I noted with my 6" telescope back in 2005 only that it was visible as a small blob. I definitely need to revisit this one.

Two observations in my log for this nebula:

The first back in 2007, under Dutch skies using an 8" SCT @ 78x / 38':

26mm Plössl: A diffuse, grey area surrounding two mag. 11 stars at a PA of 045°.

26mm Plössl, #908B Broadband Nebular: Using this filter the nebula is clearly much brighter and its is clearly a grey patch surrounding the mag. 11 stars. Especially towards the east the background is slightly patchy, too.

10 years later, in the French Ardennes in my 14" @ 168x / 29':

17mm Nagler T4: A faint, SW-NE elongated glow with two mag. 10 stars NE of the middle, aligned SW to NE. To the SW of these stars the nebula is slightly larger NW to SE. Quite a nice nebula.

17mm Nagler T4, Lumicon UHC: Using this filter it is clear that the larger part of the nebula to the SW of the mag. 10 stars is also a brighter part of the nebula, slightly tapering towards the NE. The nebula is brightest to the SW and the SSW of the two mag. 10 stars. With AV, to the ENE of the NE mag. 10 star, an interruption in the nebula is visible, a dark part with a slightly north-south elongated part to the east thereof.

17mm Nagler T4, Lumicon OIII: Comparable to the UHC filter but not as strong an effect.

Rated it 6/10 on both occasions.

Attachment 4992 Attachment 4993

Click here to download the guide.

I found several entries but will pick out three very different views with very different apertures.

20x125 binocular, no filter, NELM 6m0+, field 3° (north right)
Without filter very small (~3') but bright patch of light; looks like a unresolved star group without showing any individual stars
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16", [OIII], NELM 7m0+
1° north of NGC 7510; slightly elongated and very bright nebula with [OIII] filter without any details within the nebula; two 12mag stars within the nebula

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27", 172x, UHC, NELM 7m0+
Positive surprise, very bright nebula even without any filter; very strong [OIII] reaction, slightly Hß reaction and nicest view with UHC; with filter many details, dominating feature is a bright bean-like structure SW of the central double stars, which are located in a dark hole around
Attachment 4995
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The NGC 7538 (Sh2-158) star birth region in Perseus spiral arm is a bright and nice object even for the small aperture telescopes.

The first time seen through my 6" F/5 achro at 24x in August 2009, and ater at the magnifications of 46.9x and 60x. Without any filters the appearance has been hat of a "cotton ball" with 2 embedded stars, an OIII filter has increased the contrast and left the both stars to fade away.

The excellent sketches by Raul and Uwe are a good reason to revisit this nebula.

Clear skies,
Jiri

It begins to show some of Uwe's brightest details with 17.5" aperture.

Attachment 4996

I've just been able to see it in my 12x60 binoculars as a small, soft glow around two faint, close stars.

Scott H.