I captured the image of the presented emission nebula NGC 6164/6165 twice under the dark skies of Namibia. In one shot, I'll show it alongside the NGC 6188 nebula (the Fighting Dragons Nebula), but for now, I'd like to present it on a larger scale. The material was collected together with my colleague, Mateusz Kalisz, a participant of the expedition and the creator of the Astrolife channel.

NGC 6164/6165 (also known as PK 336-0.1, Gum 52, RCW 107, colloquially known as the Dragon's Egg) is a beautiful emission nebula located about 4200 light-years away in the constellation of Norma. It was discovered on July 1, 1834, by John Herschel. John Dreyer cataloged it in his New General Catalogue as NGC 6164 and NGC 6165. This was due to the nebula's bipolar morphology, consisting of two lobes. At first glance, it gives the impression of a planetary nebula created by an old star that has shed its outer envelope.

However, the situation appears far more intriguing than one might expect at first glance. The morphology of the nebula is due to the star HD 148937, a spectral type O star with a mass of approximately 40 solar masses and an age of only 3-4 million years. Based on stellar evolution models, it can be estimated that this incredibly rare representative of spectral type O is halfway through its existence and will spectacularly end as a supernova. Spectroscopic studies have revealed that it is a multiple-star system, and its spectral type is O6f?p (where: the question mark indicates uncertainty in classification; f - emission of N III and He II, and p - unspecified characteristics, a peculiar star).

The nebula itself is an really unusual object. Classified as an emission nebula, it spans about 4 light-years. Although initially thought to be a planetary nebula, there is now a justified belief that it was formed through gases ejected from the central star.

The nebula extends to about 4 light-years and exhibits bipolar symmetry. This gives it a resemblance to more common and well-known planetary nebulae - gaseous envelopes surrounding dying stars similar to the Sun. Similar to many planetary nebulae, it has been observed that NGC 6164 has an extensive, faintly visible envelope, which I will attempt to show in the next photo alongside the NGC 6188 nebula.

And now, we come to an explanation of why the nebula isn't entirely what it seems to be. Firstly, it's the star HD 148937, which, like many other O-type stars, influences the surrounding gas clouds from its early years with ultraviolet radiation. This causes them to glow in visible light, illuminating all the voids, indentations, or densifications shaped by the stellar wind. In one of the papers I read, there was information that the cloud of material was ejected from the star as it spun on its axis, although it is also possible that the magnetic fields surrounding the star play a significant role in the complex structure of the nebula.