Star clusters

Star cluster is a group of stars detained jointly since regards the result of gravitation. Star clusters are classified into two groups: open clusters, which have no definite shape, and globular clusters, which are spherical or nearly spherical. The open consist of a few hundred young stars, while globular clusters contain more than a thousand times that amount, and are generally very old stars. Globular clusters form a halo around our galaxy, the Milky Way, while the open is located in the spiral arms. Open clusters are much more numerous than globular: about 1,000 are known in our galaxy and there are only 140 globular.

Structures of galaxies Clusters

In the universe Galaxy clusters are huge structures. Galaxies emit a lot of gravity. These causes nearby galaxies attract each other and are merged to form clusters. Our galaxy, the Milky Way, is part of a small cluster called the Local Group . Within a cluster, galaxies rotate around each other, and even frequently collide. The size and mass of the cluster galaxies varies with the form, but the distance between one end and another is always several million light years.

How can A Stars is growth

Spitzer will present significant information on the structure and growth of stars and the circumstellar medium (surrounding the star). The discovery and characterization of circumstellar disks of gas and dust, signs of extra-solar planetary systems is one of the most important scientific goals of the Spitzer mission

Molecular gas

The giant molecular clouds are composed primarily of hydrogen, are the reserve materials from which stars form. 

Galaxies

A wide-ranging malaria program of imaging and spectroscopy of galaxies by Spitzer will conduct, from the closest to the Milky Way to those found in the limits of the observable universe.

Ultra luminous Infrared Galaxies (ULIRGs)

The satellite IRAS discovered a class of ultra luminous galaxies that radiate more than 90% of infrared light. Studies show that optical and infrared most of these objects are in systems of galaxies in collision or interaction. The study of the nature of ULIRGs and their relation to active galaxies (see next paragraph) is one of the most important problems in astrophysics.