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A Serendipitous Planetary


AusGuy
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A couple of nights ago I tried to view Cederblad 122 which is a large bright-ish emission nebula just to the south-east of The Coalsack, the prominent dark nebula which is itself to the east of the Southern Cross. Things did not go particularly well. Despite my fairly large imaging field of view of 82 x 56 arcmin the nebula was much too large to fit into a single frame. So I resorted to wandering about the area hoping to find a region that would show up nicely as a single frame. By the time that I had moved the telescope's aim 7 times I was about to give up when, on the eighth attempt I noticed a tiny but striking blue object just within the top of the camera's frame (see image 1 below). This was unexpected. I had not seen it before. So, giving up on Cederblad 122, I concentrated on this “new” object which, because of its colour, seemed likely to be a planetary nebula.

Cranking up the zoom level to 200% of the camera's native resolution (see image 2 below) produced a reasonable view of this strange looking object that seemed to have a definite “s” shaped central region surrounded by some arcing filaments. The following day I spent time on the internet to identify the object and it turns out that it is a well known planetary nebula having the NGC catalogue number 5189. It is located 1,780 light years away in the constellation Musca (the Fly). Its angular size is about 2 arcmin and that translates into a linear size of about 1.2 light years. To quote from NASA's HubbleSite “Most of the nebula is knotty and filamentary in its structure. As a result of the mass-loss process, the planetary nebula has been created with two nested structures, tilted with respect to each other, that expand away from the center in different directions. … Its double bipolar or quadrupolar structure could be explained by the presence of a second star orbiting the central star and influencing the pattern of mass ejection during its nebula-producing death throes.” Recent Observations with the Southern African Large Telescope have finally found a white dwarf companion in a 4.04 day orbit around the rare low-mass Wolf-Rayet type central star. There are a number of fine amateur images of NGC 5189 on Astrobin and a spectacular image on the HubbleSite can be found at

https://hubblesite.org/contents/media/images/3870-Image?keyword=Uranus

It just goes to show how rewarding just wandering around the sky can be. You never know what you are going to find (even if many others have long since found it before you).

Image 1 - The "discovery" image

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Image 2 - 200% resolution

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Vixen R200SS; SW AZ-EQ6 Pro; ZWO ASI294MC Pro; Baader MPCC III; Bortle 4.5

SharpCap livestack using 1 minute exposures at 300 gain

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