8 Apr. 2011

 

Delayed jets in Herbig-Haro 34

 

Studies conducted with NASA's Spitzer Space Telescope on Herbig-Haro 34, a star near the start of its life in the constellation of Orion, have showed that the clumps of gas in one of its two jets are emitted 4.5 years later than similar clumps in the other jet.
Herbig-Haro objects (named after the two researchers that first catalogued them) are the name given to the jets associated with a transient phase in the life of a young star. As the parent gas cloud undergoes collapse, a disk of dusty interstellar medium can form around the young star and symmetrical jets can develop in directions perpendicular to this disk. How the jets are formed is very uncertain, but it is likely that they are associated with the passage of sound waves from the star to the disk.
Until now, it was thought that the region around the star involved in the formation of the jets was about 30 astronomical units across (the orbital radius of Neptune), but in the case of Herbig-Haro 34, it is estimated to be only 3 astronomical units. The research team (including Alberto Noriega-Crespo of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena) were able to make this conclusion by measuring the time delay between the emission of features in one jet with respect to the other, and knowing the velocity of the jets and the sound speed in the medium surrounding the star, they could estimate the distance between the base of the two jets.
At present, Herbig-Haro 34 is the only object known to show a time delay between the two jets, something made possible thanks to the unique capabilities of Spitzer in penetrating the dusty nebular gas in which the object lies. At the infrared wavelengths used by Spitzer, the second, more obscured jet is visible (image to the right) whereas at optical wavelengths (image to the left) only a single jet is visible.

 

by Michele Ferrara & Marcel Clemens

credit: NASA/JPL-Caltech