Nebulae

The nebulae is more or less solid, evident or not from Earth. Nebulae can be found anywhere in the interstellar space. Before the invention of the telescope, the term nebula was applied to all celestial objects of diffuse appearance. As a result, many objects are now known to be star clusters of galaxies were called nebulae. Nebulae have been detected in almost all galaxies, including our own, the Milky Way. Depending on the age of stars associated, it can be classified into two groups: 1. - Associated evolved stars, such as planetary nebulae and supernova remnants. 2. - Associated with very young stars, some even still in the process of training, such as Herbig-Haro objects and molecular clouds.

Organization of the nebulae by light

But you go to the process that causes the light they produce; these nebulae can be classified into: The emission nebulae, whose radiation come from dust and ionized gas as a result of heating to which they are subjected by nearby hot stars. Some of the most striking objects in the sky as the Orion Nebula are nebulae of this type.

 The mirror image nebulae imitate and scatter light in some hot stars nearby. The Pleiades of Taurus are an example of bright stars in a reflection nebula. The dark nebulae are clouds little or no light, represented as a dark spot, sometimes surrounded by a halo of light. The reason they do not emit light themselves is that the stars are too far away to heat the cloud. One of the most famous is the Nebula Horse head in Orion. All dark bands seen in the sky when we look at the disk of our galaxy is a succession of dark nebulae.