Motions in Stellar Jets

When young stars form out of a cloud of gas and dust, they are typically surrounded by a spinning disk of material that will later coalese to form planets. At very young ages, material from this circumstellar disk accretes onto the star, and some fraction of the material is redirected into highly collimated supersonic outflows that emerge along the poles of the disk. Stellar jets can be quite spectacular visually - glowing gas from shock waves in the flow can be visible over light years from the driving star.

Remarkably, by observing with the Hubble Space Telescope over a span of several years it is possible to watch these jets move and change shape in the sky in real time. Reconstructing intermediate times allows astronomers to make movies of the motion within the jets, which clarifies how the flows interact internally and with their surroundings.

Rice professor Patrick Hartigan has led a major effort to construct these movies. The large scale movie of HH 47 shows a complex structure in the jet that moves as a unit outward from an obscured star visible only at infrared wavelengths. The jet ends in a bright bow shock, and movies of the bow shock show several clumps that penetrate into the bow and may even begin to emerge on the other side of the shock. The scenario these movies imply is one where the flows are much clumpier than previously thought, and in fact this internal structure appears to dominate the dynamics of the flows. Additional images of these regions at future times should continue to produce fascinating results.

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Patrick Hartigan