Young stars influence the medium they are borned from giving rise to spectacular phenomena.
The interstellar medium The space among the stars is not empty, it contains plenty of matter which plays an active and important role on the process of star formation and evolution of the galaxies. The last phases of the life of a star are associated to the ejection of material to the interstellar medium. The OAN astronomers study the phase of red giant and later phases of planetary and protoplanetary nebulae. External Galaxies Extragalactic astronomy consists in the study of large groups of stars considered as galaxies different from the Milky Way. In the OAN the main interest in this field is the study of the interstellar medium in other galaxies.