The Helix Nebula – NGC 7293

The Helix Nebula is one of the closest and brightest of the planetary nebulae in our sky.  Distance estimates range from 450 to 700 light years.  At the larger estimated distance the nebula’s size would be 2.5 LY across. 

The nebula consists of a bright inner ring and a faint outer ring, both consisting of the dying star’s ejected atmosphere.  The faint outer ring is just visible to the upper right of the bright inner ring in the image below.  Although it is one of the brightest planetary nebula, that brightness is spread across a large area making it a difficult object to view visually.  The outer ring has a angular size of 28 arc minutes making it about the size of the full moon.   The outer ring is expanding at a rate of about 89,500 MPH and the inner ring about 71,500 MPH.  Those speeds and size indicate the nebula is about 10,600 years old.

This image is a stack of fifty-five 120 second exposures. The nebula only rises 33 degrees above the southern horizon as seen from here and most of my southern horizon is occluded by trees. There is however, a two hour gap in the tree line. It took several days to accumulate enough exposures through that narrow window.