The whole is greater than the sum of its parts

Between the two ancient globular clusters – NGC 1466 in the west, and NGC 2257 in the east – the LMC boasts an impressive 364 NGC objects. From objects so big and bright it seems improbable that they reside in another galaxy, to those that are best described as challenging, it is a magnificent and singular experience to observe them.

However, you will notice that I have presented the NGC objects in one of two ways. Some are straightforward and pretty much how we are used to seeing objects presented, for example:

NGC 1466 (Ancient Globular Cluster)

Others are presented in a slightly different way, for example:

N11B + LH 10 = NGC 1763 (Emission Nebula + OB Association)

This is why they are presented differently:

No matter how carefully one observes the NGC objects, they don’t give you any idea of the structures in which they reside. Take NGC 1763, for instance. It inhabits the northwestern corner of the galaxy and is one of the LMC’s masterpieces. It is absolutely stunning in the telescope at all magnifications, with and without the UHC filter. But in the absence of knowing what’s going on with this nebula, that’s all it is, a gorgeous object, a visual piece of celestial poetry. But it is not. By observing it in conjunction with both its Henize emission nebula component (acronym N), and the Lucke Hodge OB association (acronym LH), one gains astrophysical insight and understanding that transforms it from a superb glowing nebula to part of a huge structure that is, frankly, mind boggling. Indeed, NGC 1763 lies in close proximity to NGC 1760, 1761, 1769, 1773, and IC 2116, and wonderful as all the objects are to observe individually, as a gestalt, they are stupendous because they are all part of the enormous superbubble, known as N11.

The “N” component…

Emission nebulae, those glowing clouds where stars are born and die, are categorized based on their unique characteristics and the physical processes at work, and include H II regions, supernova remnants, planetary nebulae, Wolf-Rayet and O-type star bubbles, each with unique compositions and origins based on the type of stars involved in their formation. The Henize catalogue lists 221 emission nebulae, many of which have associated nebular components (for a total of 415). Furthermore, the big nebulous structures, such as superbubbles and star-forming complexes, are known by their N designations, and you will find that nothing makes it easier to navigate your way through the congestion than by using these designations.

The “LH” component…

Nothing aids one’s understanding of what’s going on more than the OB associations. The massive members of OB associations have a profound impact on both their local environment, and on a galactic scale, ultimately determining the evolution of their host galaxies through their radiation, stellar winds and supernovae. The Lucke Hodge Catalogue lists 122 OB associations (96% of which are associated with nebulosity). Bubbles (blown by individual massive stars), superbubbles (blown by an entire OB association’s massive members’ lives and deaths), and gargantuan supergiant shells, the largest structures in a galaxy, (formed by multiple generations of OB associations) are all overrun with NGC objects.

So now when you turn your telescope to the fabulous NGC 1763 and its fellow NGC objects, incorporating both the superbubble’s 12 nebular components (N11A-L) and 4 LH OB associations, you get a striking visual portrait of a superbubble:

 LH 9 = NGC 1761 is the enormous star-filled central cavity, that measures 490 x 330 light-years, and is where the evolution of the superbubble all began, for it was excavated by the raging stellar winds and subsequent supernova explosions of the massive blue-white members of the OB association LH 9. Around the periphery we can see the dazzling H II regions that resulted as the stellar winds and supernovae energy ploughed into the surrounding material, compressing it and triggering the birth of the next generation of stars in three more OB associations:

LH 10 + N11B = NGC 1763 (which incidentally, is also the youngest OB association in the LMC)

LH 13 + N11C = NGC 1769

LH 14 + N11E = NGC 1773.

And to round off the NGCs in this dazzling superbubble: NGC 1760 is an emission nebula (N11F), and NGC 1773 is an open cluster. And let’s not forget little N11A = IC 2116, which lies off the northeast end of NGC 1763. It is a rare and exotic high excitation blob (and arguably the most beautiful one to observe in the Cloud). And finally, the Henize objects most often include other fascinating objects that one might otherwise overlook; in this case N11L (far right middle) which is a supernova remnant, albeit it extremely faint. 

There are also four star-sized compact clusters that we can observe lying among the stars of three of the superbubble’s OB associations:

LH 9: Brey 9 contains at least 16 early-type stars, including a Wolf-Rayet star (type WC5) and an O9-type star.

LH 10: PGMW 3070 contains 18 stars.

LH 13: (1) Sk-66°41 contains 15 components and (2) HNT 1 contains an unbeliveable 70 stars.