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The varied garden cosmic

Over the years, astronomers have come up with new technical details in order to observe the sky. A technique that has found enormous success is that of "survey", or catalogs of galaxies . These observations more or less large portions of sky in order to detect astronomical sources, especially the weakest and most distant .

The result is a map of the sky, instead of describing the position of planets and constellations, reconstructs the distribution of galaxies in the universe. For each galaxy, the light emitted is measured, the distance from us and other properties that are then used by astrophysicists to study the possible models of formation and evolution of galaxies. Over the last decade this field of astronomy has grown a lot thanks to the proliferation of ever more accurate survey.

One of the findings shared unanimously by all these surveys is that the galaxies in the universe are not distributed evenly but tend to be grouped into structures that are called groups or clusters of galaxies . If you look at regions very large universe, the same clusters appear to be part of a distribution made even more difficult to superclusters, filaments and empty regions (see diagram).

Moving from these observations to detailed models for the explanation of the processes of formation and evolution of galaxies is not easy. The basic concept however is quite familiar. Think of a survey of galaxies as a picture of a plant full of flowers. Some flowers are not yet in bloom, others are in their full splendor, and others are already dead. In this context, our minds easily trace an evolutionary sequence. The galaxies in the survey are like flowers in plants, each with a different developmental stage. It is the responsibility of astrophysical theories describe a galaxy as "blooms" and evolves. Currently, the scientific community there is general agreement on the factors that lead to the birth of a galaxy, but its developmental stages are still under debate.

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In this image from the Sloan Digital Sky Survey (SDSS ), Earth is the center and each point is a galaxy. The galaxies are color coded according to the age of their stars (the red indicates the galaxies with old stars). The zoom in the right pane shows a cluster of galaxies.