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Radio blobs at the Milky Way's center.

Radio blobs at the Milky Way's center

The most detailed portrait yet of the Milky Way's core reveals an array of huge plasma blobs just a fraction of a light-year away from an intense, compact source of radio waves. The location and orientation of these blobs of hot, ionized gas suggest they may have been expelled in opposite directions from a turbulent sea of material surrounding a massive, unseen black hole.

The newly discovered array of plasma blobs represents just one of several previously unrecognized features now apparent in the vicinity of the Milky Way's center, says Farhad Yusef-Zadeh of Northwestern University in Evanston, Ill., who described the discoveries at last week's American Astronomical Society meeting in Albuquerque, N.M. The findings support the notion that the radio source Sgr A*, which presumably envelops a black hole, marks the position of the Milky Way's active nucleus.

The galactic center lies about 25,000 light-years away from Earth in the direction of the constellation Sagittarius. To map it, Yusef-Zadeh and his collaborators used the Very Large Array radiotelescope near Socorro, N.M., measuring the intensity of radio emissions at a wavelength of 2 centimeters.

The most detailed maps show a pattern of radio-emitting plasma blobs less than 0.2 light-year from the central radio source. Farther out, the astronomers detected more blobs and a cavity about 0.3 light-years across, perhaps swept out by strong particle and radiation "winds" emanating from the center.

They also see evidence for a trail of hot, ionized gas apparently streaming from a red, supergiant star less than 1 light-year from Sgr A*. This flow, possibly driven by a powerful wind of charged particles or by intense ultraviolet radiation from the galactic center, appears as a tail pointing directly away from the central radio source.

Whereas the Milky Way's nucleus is a relatively calm place compared with the centers of some other galaxies, the kinds of activity witnessed there may be similar to those powering even the most energetic quasars and radio galaxies, Yusef-Zadeh says. "In no other nucleus do we get such a good view of what is taking place."
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Author:Peterson, Ivars
Publication:Science News
Date:Jun 23, 1990
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