In space, it is possible to locate impressive cosmic formations in every sense: from their fantastic appearance to their exquisite chemical composition. There are many, millions, but among them, a group stands out, called nebulas, which look like colorful clouds floating in the interstellar medium. They consist, mainly, of hydrogen and helium, in addition to diverse chemical elements reduced to cosmic dust. They are closely related to the stars, because they are born from the nebulae or, well, they become nebulae towards the end of their days.
The curiosity of the man led him to devise and build the telescope, with which he was finally able to observe closely the stars. However, it was not only these that they had the pleasure of observing since they also noticed the presence of other galaxies, black holes, asteroids and, of course, the nebulae. It should be noted that, previously, “nebulosa” was a word used to name anybody that had a somewhat diffuse or blurred appearance; This changed in the 19th century, when, step by step, the appropriate terms for each formation were coined.
In our days, nebulas have been classified into three groups, taking into account their emission and absorption of light. The first of these, the dark nebulae or absorption, are distinguished by being away from the stars and absorb much of the energy they radiate. Then there are reflection nebulae, which are characterized by reflecting the light of nearby stars, but whose intensity is not strong enough to excite the gases of it. Finally, there is the emission nebula, the best-known class, whose gases glow brightly, as a result of the emission of UV rays by nearby hot stars.