The Helix Nebula
Optics:   Ritchey–Chrétien 20" F/8.2 (4166mm FL) Processing:   PixInsight, Photoshop
Camera:   SBIG STXL-11000 with Adaptive Optics Date:   2014 and 2020
11 Megapixel (4008 x 2672 16-bit sensor) Location:   Columbus, Texas
Exposure:   LRGB = 640:90:80:80 minutes Imager:   Kent E. Biggs
The Helix Nebula is a Planetary Nebula located in the direction of the constellation Aquarius. The Helix Nebula is sometimes referred to as the “Eye of God” or “Eye of Sauron” due to its resemblance to a large eye. It is considered to be the closest planetary nebula to earth at under 700 light years away (4 million billion miles away or a 4 with 15 zeros!). It was discovered in the 1820’s by German astronomer Karl Ludwig Harding who discovered Juno, the third asteroid of the main-belt between Mars and Jupiter; The lunar crater Harding and asteroid 2003 Harding are named in his honor. The Helix Nebula is also known as NGC 7293 or Caldwell 63 and has some similarity in appearance to the Cat’s Eye planetary Nebula.

The central star, visible in the image above, is a relatively low mass star which continues to sluff off its outer layers as it approaches the end of its life. As it continues to lose material and collapses, it will eventual become a white dwarf having extremely high density with the mass of an entire star squeezed by gravity into the size of earth. The Helix Nebula is about 2.5 light years in size or about 150,000 times the size of the distance from earth to our sun. The gases shed formed a helix structure, hence its popular name, and from earth we look directly down that helical cylinder. The gases measured expand at about 20 miles per second, which when extrapolated backwards, gives it and age of 10-11 thousand years!

As the Helix Nebula expands into space it has begun to collide with the interstellar medium causing its sides to begin to flatten. One of the more interesting features visible in the Helix are cometary knots visible in the image above. There are hundreds of knots that, like comets, have gas and dust radially pushed directly away from the central star. For size perspective here, each of these small knots is about the size of our entire solar system of sun and planets, or several billion miles across.

There are hundreds of galaxies also visible in the image, especially when removing the stars. Note several of these galaxies are visible in the Helix. The are all many times further away than the nebula, so their light passes through the shells of material sometimes altering their color and appearance.