Star formation

Star formation is the process by which gas in molecular clouds gets transformed into stars.

In the current paradigm of star formation, cores of molecular clouds (regions of specially high density) became gravitationally unstable, and start to concentrate. Part of the gravitational energy lost in the process is radiated in the infrared, another part increases the temperature of the core. The accretion of material happen partially though a circumstellar disc[?]. When the density and temperatura are high enough, deuterium ignites, slowing down the collapse. After it is exhausted, material from the cloud continues to "rain" on the protostar. In this stage bipolar flows are produced, probably to eliminate part of the angular momentum of the falling material. Finally, hydrogen ignites in the core of the star, and the rest of the enveloping material is cleared away. The later evolution of the star is studied in stellar evolution.

Observations

Key elements of star formation are only available observing in wavelengths other that optical. The structure of the molecular cloud and the effects of the protostar is best observed in rotational transitions of CO and other molecules; this are observed in the millimiter and submillimiter range. The radiation from the protostar and early star have to be observed in the infrared astronomy, the extinction caused by the rest of the cloud where it is being formed is usually too big to allow us to observe in the visual.