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.
The Heart Nebula (IC 1805) is some 7500 light years away from Earth and is located in the Perseus Arm of the Galaxy in the constellation Cassiopeia. It was discovered by William Herschel on 3 November 1787. It is an emission nebula showing glowing ionized hydrogen gas and darker dust lanes. The brightest part of the nebula (a knot at its western edge) is separately classified as NGC 896, because it was the first part of the nebula to be discovered. The nebula's intense red output and its morphology are driven by the radiation emanating from a small group of stars near the nebula's center. This open cluster of stars, known as Collinder 26 or Melotte 15, contains a few bright stars nearly 50 times the mass of our Sun, and many more dim stars that are only a fraction of our Sun's mass. The Heart Nebula is also made up of ionised oxygen and sulfur gasses, responsible for the rich blue and orange colours seen in narrowband images. The shape of the nebula is driven by stellar winds from the hot stars in its core. The nebula also spans almost 2 degrees in the sky, covering an area four times that of the diameter of the full moon
Believed to be the cosmic fire of creation by the Maya of Mesoamerica, M42 blazes brightly in the constellation Orion. Popularly called the Orion Nebula, this stellar nursery has been known to many different cultures throughout human history. The nebula is only 1,500 light-years away, making it the closest large star-forming region to Earth making it relatively bright. Because of its brightness and prominent location just below Orion’s belt, M42 can be spotted with the naked eye, while offering an excellent peek at stellar birth for those with telescopes. It is best observed during January. The Mayan culture’s likening of the Orion Nebula to a cosmic fire of creation is very apt. The nebula is an enormous cloud of dust and gas where vast numbers of new stars are being forged. Its bright, central region is the home of four massive, young stars that shape the nebula. The four hefty stars are called the Trapezium because they are arranged in a trapezoidal pattern. Ultraviolet light unleashed by these stars is carving a cavity in the nebula and disrupting the growth of hundreds of smaller stars.