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Post Info TOPIC: Herbig-Haro 1 and 2


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HH 2
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Title: The time evolution of HH~2 from four epochs of HST images
Author: A. C. Raga, B. Reipurth, P. F. Velázquez, A. Esquivel, J. Bally

We have analyzed four epochs of H alpha and [S~II] HST images of the HH~1/2 outflow (covering a time interval from 1994 to 2014) to determine proper motions and emission line fluxes of the knots of HH~2. We find that our new proper motions agree surprisingly well with the motions measured by Herbig & Jones (1981), although there is partial evidence for a slight deceleration of the motion of the HH~2 knots from 1945 to 2014. We also measure the time-variability of the H intensities and the [S~II]/H alpha line ratios, and find that knots H and A have the largest intensity variabilities (in 1994-2014). Knot H (which now dominates the HH~2 emission) has strengthened substantially, while keeping an approximately constant [S~II]/H alpha ratio. Knot A has dramatically faded, and at the same time has had a substantial increase in its [S~II]/H alpha ratio. Possible interpretations of these results are discussed.

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RE: Herbig-Haro 1 and 2
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Title: Spitzer observations of the HH 1/2 system. The discovery of the counterjet
Authors: Noriega-Crespo, A. (1), Raga, A. C (2) ((1) Infrared Processing and Analysis Center, California Institute of Technology,(2) Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico)

We present unpublished Spitzer IRAC observations of the HH 1/2 young stellar outflow processed with a high angular resolution deconvolution algorithm that produces sub-arcsecond (approx. 0.6" - 0.8") images. In the resulting mid-infrared images the optically invisible counterjet is detected for the first time. The counterjet is approximately half as bright as the jet at 4.5 micron (the IRAC band that best traces young stellar outflows) and has a length of approx. 10". The NW optical jet itself can be followed back in the mid-IR to the position of the exciting VLA 1 source. An analysis of the IRAC colours indicates that the jet/counterjet emission is dominated by collisionally excited H2 pure rotational lines arising from a medium with a neutral Hydrogen gas density of 1000-2000 per cubic cm and a temperature of 1500 K. The observed jet/counterjet brightness asymmetry is consistent with an intrinsically symmetric outflow with extinction from a dense, circumstellar structure of 6" size (along the outflow axis), and with a mean visual extinction of Av=11 mag.

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Haro objects are small patches of nebulosity associated with newly-born stars, and are formed when gas ejected by young stars collides with clouds of gas and dust nearby at speeds of several hundred kilometres per second. Herbig-Haro objects are ubiquitous in star-forming regions, and several are often seen around a single star, aligned along its rotational axis.
Herbig-Haro objects 1 and 2.kmz
Google Sky File



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Herbig-Haro object #1 and #2 are formed when a surrounding the cloud is heated by shock waves from jets of high-speed gas being ejected from a newborn star. Because the star itself is embedded in a dusty cocoon, the Herbig-Haro objects provide the only visible clues to physical processes occurring in the young star.

Located at a distance of about 1,500 light-years, in a star-forming region of the constellation Orion, these nebulosities have catalogue designations HH1 and HH2 for their discoverers astronomers George Herbig and Guillermo Haro.HH-2 lies . The objects are located at the leading edge of a supersonic gas flow that emanates from a young star located about 1/2 light-year from the object. The star is detectable only with infrared and radio telescopes.



Herbig-Haro objects are small patches of nebulosity associated with newly-born stars, and are formed when gas ejected by young stars collides with clouds of gas and dust nearby at speeds of several hundred kilometres per second. Herbig-Haro objects are ubiquitous in star-forming regions, and several are often seen around a single star, aligned along its rotational axis.

HH objects are transient phenomena, lasting only a few thousand years at most. They can evolve visibly over quite short timescales as they move rapidly away from their parent star into the gas clouds in interstellar space (the interstellar medium or ISM). Hubble Space Telescope observations reveal complex evolution of HH objects over a few years, as parts of them fade while others brighten as they collide with concentrations of material in the interstellar medium.

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