The Helix Nebula, also known as The Helix, NGC 7293, is a large planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludwig Harding, probably before 1824, this object is one of the closest to the Earth of all the bright planetary nebulae. The estimated distance is about 215 parsecs or 700 light-years.
The Helix Nebula is thought to be shaped like a prolate spheroid with strong density concentrations toward the filled disk along the equatorial plane, whose major axis is inclined about 21° to 37° from our vantage point. The size of the inner disk is 8×19 arcmin in diameter (0.52 pc); the outer torus is 12×22 arcmin in diameter (0.77 pc); and the outer-most ring is about 25 arcmin in diameter (1.76 pc). We see the outer-most ring as flattened on one side due to its colliding with the ambient interstellar medium.
Expansion of the whole planetary nebula structure is estimated to have occurred in the last 6,560 years, and 12,100 years for the inner disk. Spectroscopically, the outer ring’s expansion rate is 40 km·s−1, and about 32 km·s−1 for the inner disk.
Imaging telescopes or lenses: PlaneWave Instruments Planewave 20″ CDK
Imaging cameras: FLI PL6303E
Mounts: Planewave Instruments Ascension 200HR
Filters: Astrodon Blue, Astrodon Green, Astrodon Red, Astrodon Luminance
Dates: July 3, 2014, July 26, 2014
Astrodon Blue: 2×300″ bin 2×2
Astrodon Green: 2×300″ bin 2×2
Astrodon Luminance: 17×300″ bin 1×1
Astrodon Red: 2×300″ bin 2×2
Integration: 1.9 hours
Author: Giulio Ercolani
AstroPhotography of the day by SPONLI 5 Aug 2014