Radio Waves Detected Coming From Center of Galaxy

March 2, 2005

Astronomers have detected an unusual, powerful burst of intermittent radio waves emanating from the direction of the center of our galaxy.

Now the search is on to trace the source of the mystery radio bursts, or at least find more like it. Was it a dying star "burping" its last radio emissions? Or is there something out there completely new to science?

The discovery "will cause a stampede of further observations," write astronomers Shri Kulkarni and Sterl Phinney in tomorrow's issue of the science journal Nature. They're in the Division of Physics, Mathematics, and Astronomy at the California Institute of Technology in Pasadena.

Astronomer Scott Hyman of Sweet Briar College in Virginia helped make the discovery while observing the center of the Milky Way through radio telescopes set at various wavelengths. The galaxy is full of objects that emit radio waves, including black holes and stars of various kinds. But the cause of this particular burst of radio waves has astronomers scratching their heads.

"The most spectacular aspect of this is that five bursts occurred at regular intervals of about an hour and a quarter [77 minutes]," Hyman said. "They were at a constant intensity … and each burst had basically the same time profile." Each burst lasted about ten minutes.

Hyman and colleagues reported their findings in this week's Nature.

Transient radio emissions are not particularly unusual. They generally occur, at many different wavelengths, in conjunction with large releases of energy such as occur during deaths of stars. Binary systems featuring black holes or neutron stars emit radio and x-ray bursts, while supernovas emit over the entire electromagnetic spectrum.

But short-lived radio bursts are rarely detected, because radio telescopes, until recently, have only been able to focus on a relatively small area of the sky in each observation.

"We need a different way of building telescopes," Kulkarni said. "Now we have very sensitive instruments, but they have tunnel vision. They are good when you know what you want to see but not so good [for looking] at a large piece of sky and being ready to pounce on something."

Kulkarni added that discoveries like Hyman's could galvanize astronomers to press on with the development of more "wide sky" radio instruments.

Hyman's team was able to achieve a considerably wider sky view than other astronomers have.

"If we found this by just scratching the surface, imagine what's lurking out there," he said. "We may uncover many additional types of lower-energy-radio transient sources."

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