Astronomers studying the fast-moving jet of material ejected by a still-forming, massive young star found a major difference between that jet and those ejected by less-massive young stars. The scientists made the discovery by using the National Science Foundation's Karl G. Jansky Very Large Array (VLA) to make the most detailed image yet of the inner region of such a jet coming from a massive young star. José-Maria Torrelles, from the Institute of Space Sciences (ICE-CSIC) has participated in this collaborative work, that has involved scientists from UNAM (México), INAF (Italy), University of Leeds (UK) and ESO.

The team of scientists observed a massive protostar called Cep A HW2, located about 2,300 light-years from Earth in the constellation Cepheus. Cep A HW2 is expected to develop into a new star about 10 times more massive than the Sun. The new VLA images showed the finest detail yet seen in such an object, giving the astronomers their first view of the innermost portion of the jet, a portion roughly as long as the diameter of the Solar System.

According to the astronomers, the discovery raises two main possibilities: first, the same mechanism could be at work in both high-mass and low-mass protostars, but the collimation distance could be determined by the mass, occurring farther away in more-massive systems. The second possibility is that high-mass stars might produce only the wide-angle wind seen in Cep A HW2, with collimation only coming when physical conditions around the star restrict the flow.

The researchers are reporting their findings in The Astrophysical Journal Letters.