Hexagons in nature are fascinating to me – straight-sided symmetric structures seem unusual when they occur in the natural world.  The hexagon at Saturn’s north pole has captured everyone’s attention, but hexagons also occur in other places, including galaxies.  The formation mechanism for these galaxy hexagonal structures is not yet well understood.  I have read explanations which describe diocotron instability,  plasma physics, and nonlinear hydrodynamics, but not one that I have clearly understood yet.

Unlike the Saturn hexagon, galaxy hexagons are not as cleanly defined.   They seem to develop most symmetrically when there is no disturbance to the galaxy disk.  Gravitational disturbance, in terms of nearby small galaxies, seem to create havoc in local areas of the hexagonal structure.  Even in the best of examples, galactic hexagons can take a bit of imagination to trace them out.  But once your eyes get used to seeing them, they are much easier to recognize, which is one of the reasons for compiling this poster. I included the hexagon mouseover to help with the visualization.

The galaxies shown in the poster display hexagons primarily in the mid-disk region, around the brighter inner region.  They are some exceptions, where the hexagon structure rims the outer disk.

I am curious about the possible overlap in the development mechanism and physics between these hexagons and Vorontsov-Velyaminov rows.  V-V rows are unusually straight segments of galaxy spiral arms. The length of a V-V row increases linearly with distance from the core.  The average value of the angle between rows is 120 degrees, the same as the included angle of the hexagon.   However, many of the classic V-V examples are for single arms in the outer portion of the disk, which is different than the hexagons described here.

If you would like to read more about any of these objects on the poster, each of them has previously been uploaded and described individually on Astrobin. They all reside in my Astrobin Hexagons Collection.

If you would like to access all my DSO compilation posters, please click here.