The Omega Nebula Messier 17 (M17, NGC 6618), also called the Swan Nebula, the Horseshoe Nebula, or (especially on the southern hemisphere) the Lobster Nebula, is a region of star formation and shines by excited emission, caused by the higher energy radiation of young stars. Unlike in many other emission nebulae, however, these stars are not obvious in optical images, but hidden in the nebula. Star formation is either still active in this nebula, or ceased very recently. A small cluster of about 35 bright but obscurred stars seems to be imbedded in the nebulosity.

The Lagoon Nebula (catalogued as Messier 8 or M8, and as NGC 6523) is a giant interstellar cloud in the constellation Sagittarius. It is estimated to be between 4,000-6,000 light-years from the Earth. In the sky of Earth, it spans 90′ by 40′, translates to an actual dimension of 110 by 50 light years.

The Eagle Nebula (catalogued as Messier 16 or M16, and as NGC 6611) is a young open cluster of stars in the constellation Serpens, discovered by Jean-Philippe de Cheseaux in 1745-46. Its name derives from its shape which is resemblant of an eagle. It is the subject of a famous photograph by the Hubble Space Telescope, which shows pillars of star-forming gas and dust within the nebula.
The Eagle Nebula is part of a diffuse emission nebula, or H II region, which is catalogued as IC 4703. This region of active current star formation is about 6,500 light-years distant. The tower of gas that can be seen coming off the nebula is approximately 57 trillion miles (97 trillion km) high.

 

The Trifid Nebula (catalogued as Messier 20 or M20 and as NGC 6514) Its name means ‘divided into three lobes’. The object is an unusual combination of an open cluster of stars, an emission nebula (the lower, red portion), a reflection nebula (the upper, blue portion) and a dark nebula (the apparent ‘gaps’ within the emission nebula that cause the trifid appearance; these are also designated Barnard 85). Viewed through a small telescope, the Trifid Nebula is a bright and colorful object, and is thus a perennial favorite of amateur astronomers.

The “Ring Nebula”

is located in the northern constellation  of Lyra, and also catalogued as Messier 57, M57 or NGC 6720. It is one of the most prominent examples of the deep-sky objects called planetary nebulae (singular, planetary nebula), often abbreviated by astronomers as simply planetaries or PN.