Data from ISO, the infrared observatory of the European Space Agency (ESA), have provided the first direct evidence that shock waves generated by galaxy collisions excite the gas from which new stars will form. The result also provides important clues on how the birth of the first stars was triggered and speeded up in the early Universe.
More at:
http://www.esa.int/esaCP/SEM7SVRMD6E_index_0.html