A Radio Atlas of the Milky Way's Core

AUSTIN, TEXAS--A freshly reprocessed image from 27 radio telescopes has given astronomers their largest and clearest view yet of the turbulent core of the Milky Way. The image, unveiled here last week at an American Astronomical Society meeting, sheds light on the magnetic influence of the black hole thought to lie at the galaxy's hidden heart.

Surrounding the black hole at the center of our galaxy is a maelstrom of crowded stars and energetic particles. Thick veils of gas and dust shield the core from our view. However, radio waves penetrate the fog to reveal hot cradles of baby stars, ghostly outlines of ancient supernova explosions, and glowing bands that follow the paths of intense magnetic fields. Ten years ago, radio astronomers at the Very Large Array in Socorro, New Mexico--a Y-shaped bank of telescopes made famous in the movie Contact--tried to capture this large region in a single image. But as a result of subtle geometric errors, caused by the Earth's curvature and slight differences in the telescopes' elevations, only the central part of the image was clear. Computer programs of the day couldn't fix this.

Using faster computers and software, radio astronomers at the Naval Research Laboratory in Washington, D.C., have removed those distortions to produce a strikingly sharp radio atlas of a swath of sky as broad as eight full moons. "This is by far the widest field of view of the galactic center at high resolution," says team leader Namir Kassim. The improved clarity reveals several new patterns of glowing gas, including a supernova remnant (upper arrow) and a bright band called the "Pelican," for its birdlike profile at high magnification (lower arrow). The Pelican lines up parallel to the plane of the galaxy, Kassim notes, whereas all other bands are perpendicular. This may mean that the Milky Way's magnetic field twists into surprisingly complex shapes near the black hole.

The display is "magnificent," says radio astronomer K. R. Anantharamiah of the Raman Research Institute in Bangalore, India, who helped collect the original data during visits to New Mexico in the 1980s. "There is no such image to compare." He notes that it will serve primarily as a "finder atlas," guiding astronomers who wish to zoom in on noteworthy features.