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Jets from a Three-Star System
Hubble Space Telescope images in infrared light, combined with ground-based radio observations, reveal three young stars located near a huge torus, or donut, of gas and dust from which they formed. This torus is tilted edge-on and can be seen as a dark bar near the lower left of the picture. However, what's surprising is that the stars are not located at the center of this donut. Instead, a pair of stars is offset to one side, below the torus, while the third star is off to the other side, far above it. Newborn stars are normally found precisely in the centers of such donuts of proto-stellar material.
The pair of stars below the donut coincides with the point of origin of huge jets of gas blasted into space by one of the twin stars. Each oppositely directed stream is 12 light-years long. (Only the jet to the right is shown here.) The star system is about 1,400 light-years away.
"It's mind-boggling that small stars like this can have such a profound influence on their environment," says Bo Reipurth of the University of Colorado, who headed the research team that photographed the region with HST's infrared and visible-light cameras.
It appears that a gravitational brawl among the stars occurred a few thousand years ago and kicked out one member. As a result, the two other stars were joined together as a tight binary pair and flew off in the opposite direction. Computer simulations of three-body stellar interactions support such a scenario. But, future observations to directly measure the motions of the stars will be needed to confirm this conclusion.
The components of the binary star are so close to each other - within five billion miles - that even Hubble does not resolve them. But the radio observations, with the Very Large Array in New Mexico, show two pairs of stellar jets almost at right angles, implying that what appears in the Hubble Space Telescope images as a single object really is two separate stars, each of which drives an outflow consisting of pairs of oppositely directed jets.
These observations may provide an important clue to how the masses of stars are determined. Now that the newborn stars are outside the giant donut, they can no longer feed on the rich supply of gas and dust in the abandoned torus. And so they can no longer grow. Thus, in this case, the three-body interaction determined the stars' final masses.
Newborn stars grow - and at the same time produce giant jets - by ingesting large quantities of gas and dust. Since each component of the close binary still produces jets, the stars must still retain small inner gas disks for fueling the continuing outflow activity.
These inner disks must have been dragged along for the ride as the stars were ejected from the center of the giant torus. But as these small reservoirs are depleted, the remarkable jet activity should begin to fizzle out.
The huge jet seen in Hubble's visible-light images comes from one of the members of the binary. This star spews out streams of gas in opposite directions, like water from a garden hose. It is not a smooth flow, but rather happens episodically, creating lumps of gas that fly across space at over one million miles per hour. These gaseous cannonballs catch up with and "rear-end" slower moving blobs, creating a pattern that resembles a string of Christmas lights embedded in the jet.