New clues refute the ideas of massive star formation

The supersonic jet and the accretion disk survive the destructive effects of ultraviolet radiation that accompanies the birth of a massive star.

Massive stars emit much ultraviolet radiation. Such molecules and radiation destroys surrounding dust generating ionized gas, which in turn hinders the growth process of the star. It is for this reason that theories suggesting that the model of a small birth through a protoplanetary disk of gas and dust star was not applicable to high-mass stars. However, this new research goes in the opposite line.

    The young star studied G345.4938 + 01.4677, is located in the constellation Scorpio and has a mass 15 times greater than the sun. This is where scientists discovered at least three significant milestones. "The first is to detect an emerging supersonic jet of the forming star within the region of ionized gas. This suggests that the accretion disk and the jet of gas are strong enough to survive despite the damage caused by ultraviolet light "explains Andrew Guzman, principal investigator and postdoctoral researcher at the University of Chile.

    In parallel and thanks to the technology frontier ALMA, found first direct evidence of the effect of electric fields on the emission lines of hydrogen. "The detection of this phenomenon called Stark effect was possible due to the high density of gas around the star, and the extraordinary sensitivity of ALMA" says Guido Garay, Director of the Department of Astronomy at the University of Chile and co-author .

    "Thanks to the high sensitivity and angular resolution of ALMA could detect a rotating around a massive star disk, first, witness the effects of electric fields on hydrogen emission lines of a jet from the same star" he said Lars Nyman, Head of Science Operations ALMA and co-author of the research.

MOLECULAR GAS AND Polbo orbiting the star

    The third major milestone is the discovery of molecular gas and dust rotating around the massive star. This finding extends the observation of protoplanetary disks at high mass regime, where the dynamics is dominated by the mass of the disk and not from the central star. While it is estimated that there are 56 solar masses on the disc, compared with 15 solar masses in the central star, the disk rotation is perfectly aligned with the jet of ionized gas, suggesting that the supersonic gas jet is being accelerated and aligned from an accretion disk.

    In the near future, "expect to find and study more jets associated with this type of ionized regions hyper compact. No ALMA really would be impossible to better characterize the accretion in this massive star, and determine if it is part of a binary system," says Guzman .

Bu Haber için yorum yapabilirsiniz 24.02.2015 12:39:25 207.241.229.214

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