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 12th 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!”

n7538calvert.jpg
©Fred Calvert/Adam Block/NOAO/AURA/NSF


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