An Artist’s Impression of The Helix Nebula - NGC 7293
The Helix Nebula (NGC 7293) is a large planetary nebula located in the constellation Aquarius. The Helix Nebula’s estimated distance from earth is about 215 parsecs or 700 light-years. The Nebula has sometimes been referred to as the “Eye of God” in pop culture because of it’s eye like appearance. It was the first planetary nebula discovered to contain cometary knots, which can be seen as globs with tails around the center of the “pupil”. Astronomers have sense discovered similar structures in other planetary nebulae and use the Helix Nebula as a base case for comparison. There are more than 20,000 cometary knots estimated to be in the Helix Nebula. These knots remain somewhat of a mystery to astronomers.
Originally, the word “nebula” referred to almost any extended astronomical object (other than planets and comets). The etymological root of “nebula” means “cloud”. As is usual in astronomy, the old terminology survives in modern usage in sometimes confusing ways. We sometimes use the word “nebula” to refer to galaxies, various types of star clusters and various kinds of interstellar dust/gas clouds. More strictly speaking, the word “nebula” should be reserved for gas and dust clouds and not for groups of stars.
By order in which they appear from top to bottom, left to right, here are the main types and some provided examples for visual reference:
Planetary Nebulae: Sh2-188
Planetary nebulae are shells of gas thrown out by some stars near the end of their lives. Our Sun will probably evolve a planetary nebula in about 5 billion years. They have nothing at all to do with planets; the terminology was invented because they often look a little like planets in small telescopes. A typical planetary nebula is less than one light-year across.
"New reprocessed. This time the sum total of Narrow Band + RGB + Luminance Halfa shots, treated with stars."
The Pelican Nebula is an H II region associated with the North America Nebula in the constellation Cygnus. The gaseous contortions of this emission nebula bear a resemblance to a pelican, giving rise to its name. [**]