Starless version of NGC7293. The Helix Nebula is a planetary nebula located in the constellation Aquarius, at a distance of 655 light years. Its age is about 10,600 years.
NGC7293 is one of the brightest and closest planetary nebula to earth. A beautiful sight in a small telescope, the central bright region extending almost half the size of the full moon. This class of planetary nebula is the end of life of smaller stars, like our sun, not large enough to explode as a nova. These smaller stars become planetary nebula when they expel their outer envelopes at the end of life.
Given the number of stars in the galaxy and the relative age it is estimated that (3) stars die in this way each year. The stars become white dwarfs – hot remnant stellar cores – that energize the ejected material. White dwarfs are very dense, typically packing a mass similar to that of the Sun into a volume comparable to that of the Earth. The intense ultraviolet radiation from these stars causes the ejected layers of gas to glow, planetary nebula.
The bright body of the helix is a disk inclined 30 degrees. Perpendicular to that disk is another pair of spherical features extending east, up in this image and west, down in this image. Also evident are shock fronts that extend about the size of the full moon up and down in the image..
Spectrum of a typical planetary nebula with high excitation shells. Note the teal color of the OIII emission line at 500.7nm that dominates the bright central structures. The weaker bluish Hbeta line at 486.6nm and the dominant Halpha line at 656.3nm.
This image was taken over several months with a total of more than 15 hours. 143 approved sub-frames using Astrodon filters Halpha, OIII and RGB
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