Identical jet lags behind twin
BY DR EMILY BALDWIN
Posted: 05 April 2011
Two seemingly symmetrical jets shooting out knots of gas and dust from opposite sides of a growing star have now been found by the Spitzer Space Telescope to lag behind each other by four and a half years.
Stars form at the centre of a spinning, collapsing cloud of gas and dust. As material folds into the stellar core, a disc of material forms around its equator, with twin jets of gas and dust blasting from above and below the disc that slows down the spinning cloud. Once the star ignites, the jets die out and the disc thins, with planet formation occurring in any clumps that remain.
Visible light image of the baby star in which one jet can be seen (left) and Spitzer's infrared view of the same star (right), which reveals the identical jet shooting off in the opposite direction to the first.
One jet of a stellar pair located 1,400 light years away in the Orion constellation and collectively known as Herbig-Haro 34, was already well-studied, but its twin remained obscured by a dark cloud until Spitzer's infrared eyes pierced the intervening dust. By scrutinizing the separation between succeeding clumps of material knotted into the jets, astronomers revealed that for every knot of material punched out by one jet, a similar knot is shot out in the opposite direction 4.5 years later. The time delay also allowed the astronomers to home in on the size of the zone from which the jets originate, confining them to within three astronomical units of the star (1 AU is the separation of the Earth from the Sun), ten times smaller than previous estimates.
“Where we stand today on Earth was perhaps once a very violent place where high-velocity gas and dust were ejected from the disc circling around our very young Sun,” says lead author of the research Alex Raga of the Universidad Nacional Autónoma de México. “If so, the formation of planets like Earth depends on how and when this phenomenon ended. Essentially, every star like our own Sun has gone through a similar cloud-disc-jets formation process.”
The team suggest that some kind of communication is going on between the two jets, likely carried by sound waves, but further investigation will be required, at Herbig-Haro 34 and other symmetrical jets, to determine the root cause of the time lags.
The new research is presented in the 1 April issue of Astrophysical Journal Letters.
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