After posting some easy OOTW last times, we go harder today.
The current object was missed by Herschel but discovered by the IRAS satellite, which was searching after infrared sources. After selecting objects by its IRAS colour to find another "Egg Nebula" to prove the protoplanetary nebula theory, Hu et al. [1993A&A...273..185H] and Kwok et al. [1996ApJ...472..287K] photographed IRAS 17150-3224. Equipped with the best ground-based telescopes both groups could verify two lobes with a dark dust lane in the middle. Later on, the revolutionary image of the HST shows the two lobes in all its beauty and detail [1998ApJ...501L.117K]. Sun Kwok invented the name "Cotton Candy". Later on, Su et al. [2003AJ....126..848S] and other scientific papers, even SIMBAD refer to this designation.
But what is this object? To make the loooong story short - our Candy belongs to the protoplanetary nebula (PPN), that means the evolutionary stage between the end of the asymptotic giant branch (AGB) stage and the planetary nebula (PN) stage of an intermediate-mass star.
Somewhat longer, but without getting a scientific paper - within this short period, the strong infrared shining central star (CS) illuminates the ejected shells. The envelope shape changes from spherically symmetric (concentric rings) to axially symmetric and forms the frequently observed bipolar structures, depending on the line of sight. The remaining dust, usually donut-shaped around the CS, blocks the light and forms the constricted morphology between the bipolar outflows. The star itself is still not hot enough to ionize the surrounding remnants, causing the visible nebula to be a reflection nebula.
The special of our Candy are the series of concentric, circular arcs. As with the objects NGC 6543, NGC 7027 or the Egg Nebula they suggest that the wind of the AGB is not steady and causes these "puffs".
But what about observing this small thing? I recorded two observations in my PPN project, both from the pristine sky of Namibia with larger telescopes. Believing reports in the internet, the object should be visible from up to 15-inch. But hopefully you know it better and let us know.
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