Puzzling radio blasts

Astronomers are stumped by powerful radio wave hiccups that appear to have emanated from near the center of our galaxy. Scott Hyman of Sweet Briar (Va.) College and his colleagues recently discovered the radio bursts while analyzing a survey of the Milky Way’s center taken in 2002 with the Very Large Array radio telescopes near Socorro, N.M.

RADIO MYSTERY. Radio wave image of the Milky Way’s core shows source (green) of puzzling blasts. N. Kassim, et al., NRL, NRAO, AUI, NSF

The team found five radio bursts, each lasting about 10 minutes and spaced 76 minutes apart, on the night of Sept. 30. The blasts were surprisingly intense, briefly rivaling the power of the radio emissions from the presumed supermassive black hole at the galaxy’s center.

The bursts, which appear to have come from a source some 600 light-years from the galactic core, had never been detected before the 2002 survey and have not been noted since, the researchers note in the March 3 Nature.

Having taken 2 minutes to reach their peak intensity, the bursts don’t resemble the fast-peaking radio blasts generated by pairs of dense, rapidly rotating stars.

The extraordinarily high magnetic field of exotic stars known as magnetars could act as both an energy source for the radio waves and a brake that could slow a star’s rotation, producing a beaconlike energy source with the 76-minute interval between bursts, Hyman speculates.

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