Discover the astronomical wonder of NGC 6164/5, known by many names including PK 336-0.1, Gum 52, and RCW 107. This emission nebula, situated on the fringes of the Ara and Norma constellations, lies approximately 3,900 light-years away from us. Its discovery dates back to the 1st of July 1834, credited to the renowned astronomer, John Herschel.
A Closer Look at NGC 6164/5
At first glance, NGC 6164/5 may seem to be a planetary nebula - a shell of gas and dust thrown off by an old, low-mass star. This initial impression stems from its bipolar morphology, composed of two distinct lobes. However, a closer inspection reveals its true nature - an emission nebula, birthed and energized by its central star, HD 148937.
The Central Star: HD 148937
HD 148937, the heart of the nebula, is a young O4-type star. With an estimated age of between three to four million years, this luminary is considered to be at the midpoint of its lifespan. Its mass, approximately 40 times that of our sun, further substantiates its classification within stellar evolution models.
The Nebula's Unique Structure
The nebula's unique, S-shaped structure, with its rounded corners and a diagonal bar encircling HD 148937, is a product of material ejected from the star itself. This nebula spans an impressive 4.2 light-years, a testament to the power of HD 148937.
A Spectacular Image of NGC 6164/5
The accompanying image, a composite optical portrayal of NGC 6164/5, was captured using a small amateur telescope. It showcases the nebula's emission of ionised oxygen ([O III]), ionised hydrogen (Hα), and ionised sulphur ([S II]). This wider field of view also reveals a halo-like structure encasing NGC 6164/5. Given its remarkable appearance, it has aptly earned the nicknames 'Dragon’s Egg' and 'Halo'.
Image Credit: Rowan Prangley @astrobin
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