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Young stellar objects often drive powerful bipolar outflows which evolve ontime scales of a few years. An increasing number of these outflows has beendetected in X-rays implying the existence of million degree plasma almostco-spatial with the lower temperature gas observed in the optical and near-IR.The details of the heating and cooling processes of the X-ray emitting part ofthese so-called Herbig-Haro objects are still ambiguous, e.g., whether thecooling is dominated by expansion, radiation or thermal conduction.  We present a second epoch Chandra observation of the first X-ray detectedHerbig-Haro object (HH 2) and derive the proper-motion of the X-ray emittingplasma and its cooling history. We argue that the most likely explanation forthe constancy of the X-ray luminosity, the alignment with the optical emissionand the proper-motion is that the cooling is dominated by radiative lossesleading to cooling times exceeding a decade. We explain that a strong shockcaused by fast material ramming into slower gas in front of it about ten yearsago can explain the X-ray emission while being compatible with the availablemulti-wavelength data of HH 2.

The evolution of the X-ray emission of HH 2 - Investigating heating and cooling processes