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CORDIS - Risultati della ricerca dell’UE

Galactic molecular clouds and star formation

Final Activity Report Summary - GMCSF (Galactic molecular clouds and star formation)

Stars and planets were not present at the beginning of the Universe but have formed by a chain of complex and fascinating physical processes occuring on multiple spatial scales and over timescales enormous to us but tiny compared to that of the Universe. To understand the origin of our Sun and planets we can observe current, ongoing star formation occuring in our immediate vicinity - in our own Galaxy, the Milky Way.

Astronomical observations made over the last century have revealed that star formation occurs in giant molecular clouds which are often many tens of light years across, and contain millions of solar masses of material. These clouds are exceptionally cold (only 10 degrees or so above absolute zero). By terrestrial standards they are incredibly tenuous (only a few thousand molecules per cubic centimetre) but by interstellar standards, molecular clouds are very dense indeed. To investigate the physical processes occurring in molecular clouds that lead to star formation, we need to observe them at wavelengths of a few millimetres or less (in the submillimetre and far-infrared parts of the electromagnetic spectrum), since at these wavelengths they shine brightly. Using telescopes fitted with detectors sensitive to this part of the spectrum we can identify and study the early stages of star formation, when the initial conditions for the eventual stars are set. The clouds from which the stars form are highly turbulent and have internal supersonic motions of several kilometres per second. We can study these internal motions, which gravity must ultimately overwhelm, by observing 'spectral lines' emitted at precise frequencies by the clouds' constituent molecules.

The GMCSF project aims to find all the locations in our Galaxy where stars are just beginning to form out of the turbulent molecular clouds and determine the dominant physical processes that control how stars form. We have surveyed almost a quarter of our Galaxy for molecular clouds to produce a map of all the locations where stars could form. The molecular clouds provide the raw material from which stars must be made. We have measured the amount of turbulence present in the clouds, and investigated the origin of the turbulence and its role in shaping the structure of the clouds. In the near future, a map of all the newly-forming stars ('protostars') present in these clouds will be constructed, which will allow us to investigate how these protostars are created.