26 December 2016 | NGC 5189

NGC 5189

Credit: CHART32 | Processing: Johannes Schedler | Click image to enlarge

Image Data

  • Date: 2013 – 2016
  • Camera: FLI Proline 16803
  • Filters: Baader + Astrodon
  • Optics: 80cm f/7 Astrooptik Keller corrected cassegrain
  • Exposure time: Ha 13x20min, OIII 4x20min, RGB each 80 min

Shining in southern skies towards the constellation Musca, NGC 5189 is a resplendent example of the population of approximately 3600 planetary nebulae in the Milky Way. Its impressive S-shaped spiral structure has elicited the attention of both amateur and professional astronomers for many years since its discovery by James Dunlop in 1826.

Exhibiting a highly complex structure of dozens of interlocking filamentary and knotty structures, the complicated and twisted morphology of NGC 5189 was long suspected to be caused by a binary central star but unfortunately evidence for one was lacking. However, the central star of NGC 5189 was found to have a companion in 2015 finally providing proof for the binary hypothesis!

Its polysymmetric structure arises from multiple interacting outflows aligned with a precessing symmetric axis centred on the binary central star. The intensely dizzying structure also consists of polar caps on a north-south axis comprised of many multitudinous cometary knots, a type of low ionisation structure that is found in other planetary nebulae such as the Helix Nebula and the Dumbbell Nebula. Past outflow activity is also the likely explanation for the central torus.

Velocity measurements of the gas undertaken as part of professional studies have shown that as it expands, the southern half is moving towards us (blueshifted) and the northern half is moving away (redshifted). This is likely to be a consequence of a bipolar outflow caused by jets launched from an accretion disk encircling the central star companion. This type of binarity based morphological trait has been found in other planetary nebulae known to contain a binary central star, most notably the Necklace Nebula and Fg 1.

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