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.
