The “ Eye of God” or The Helix Nebula (NGC 7293) is a planetary nebula located in the constellation Aquarius, at about 650 light years from the Earth. Discovered by Karl Ludwig Harding in the early 19th century, Helix is one of the closest of all the bright planetary nebulae. The central star of the Nebula, a white dwarf remnant of the star that exploded about 10,000–12,000 years ago, gives the resemblance of an eye. When a star like the Sun runs out of fuel, it expands and its outer layers puff off, and then the core of the star shrinks. This phase is known as a "planetary nebula," and astronomers expect our Sun will experience this in about 5 billion years. The blue-green glow in the centre of the Helix comes from oxygen atoms shining under effects of the intense ultraviolet radiation of the 120 000 degree Celsius central star and the hot gas. Further out from the star and beyond the ring of knots, the red colour from hydrogen and nitrogen is more prominent.
Spotted by Charles Messier in 1764, M27 was the first planetary nebula ever discovered. The term “planetary nebula” is a bit of a misnomer based on the nebula’s round, planet-like appearance when viewed through smaller telescopes. The nebula is the result of an old star that has shed its outer layers in a glowing display of color. M27 hosts many knots of gas and dust. As depicted in Hubble’s image, some look like fingers pointing at the central star, located just off the upper left of the image; others are isolated clouds, some with and some without tails. Their sizes typically range from 17 billion to 56 billion kilometers, which is several times larger than the distance from the sun to Pluto. Each contains as much mass as three Earths. These dense knots of gas and dust seem to be a natural part of the evolution of planetary nebulas. They form when the stellar winds are not powerful enough to blow away a larger clump of matter but are able to blow away smaller particles, creating a trail behind the clump. The shapes of these knots change as the nebula expands. Similar knots have been discovered in other nearby planetary nebulas that are all part of the same evolutionary scheme. Also known as the Dumbbell Nebula, M27 resides more than 1,200 light-years away in the constellation Vulpecula. With an apparent magnitude of 7.5, the nebula can be spotted with a small telescope most easily in September.
