Herbig-Haro objects

Herbig-Haro object A bright object associated with young stellar object, probably due to a region of ionisation associated with high-speed polar jets. 

Herbig-Haro objects are often found to be associated with molecular outflows observed in rotational lines of cosmically abundant molecules (e.g. CO, NH3) that come from regions enveloping the jet. The outflow velocity is generally much lower. The origin of these molecular outflows is not clear either they result from winds from the accretion disk or from the interaction between the jet and its surroundings. 

Herbig-Haro objects emission-line nebulae which are produced by shock waves in the supersonic outflow of material from young stars also referred to as Herbig-Haro nebulae. 

T Tauri star An unstable young variable star in its pre-main sequence phase (see Hertzsprung-Russell diagram). The instability, brought about by the beginning of nuclear fusion in the core of the star, causes pulsations and stellar winds, possibly with bipolar outflows. Groups of such stars, often associated with Herbig-Haro objects, are called T Tauri associations. 

The study of the chemical and physical processes occurring in T Tauri outflows is of great importance as these stars have been proposed as the energy source of Herbig-Haro objects (Schwartz 1978 Canto 1978) and turbulence in molecular clouds (Norman and Silk 1980, Franco 1983). In this work, the physical model of the outflow is taken from Hartmann, Edwards and Avrett (1982) in which the primary stellar wind (i.e. wind that has not interacted with its environment) is ionized and heated by Alfven waves in the star s convection zone to reach a terminal velocity (of about 230 kms ) and a maximum temperature (of 20,000 K, cf. Hartmann et al. model no. 2) at z = 3 to 5, where z is the radial ordinate in units of stellar radii (r t 2 x 10 cm). Thereafter the wind expands and cools radlatively and adiabatically. Other parameters for the model are the initial wind density at z = 1 (oq lO - cm ), the density at z = 5 (n < 5 X 10 to 10 cm ) and the stellar photospheric temperature 4000 E). The cooling rate of the wind is obviously dependent on the physical conditions within the ejecta and in any case is by no means certain. Hartmann et al. suggest a... 

What I wanted to point out to you is this all over this fidd there are outflows from young stellar objects (presumably Herbig-Haro objects) there are holes where the HU regions are systematically destroying the molecular hydrogen through ultraviolet irradiation there are filaments of fluorescent gas all over the place. If 1 was to show you this picture and to tell you that one of these filamoits is unique and special, and invite you to pick it out, I am really skeptical that you would choose the Orion Bright Bar. 

In heavily obscured regions with ongoing star formation one observes the so-called Herbig-Haro (HH) objects thin collimated jets of matter rapidly flowing (up to several hundred kilometers per second) out from young stellar objects. An example is shown in Fig. 2.11. These jets are mainly associated with Class 0 and I objects but sometimes are also observed for T Tauri stars. The outflows interact with... 

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