Take it to the max: supernova in overdrive.

Of all the things that go bang in the sky, astronomers have ranked supernovas as the most powerful. In these explosions, a star hurls its outer layers into space at 10 percent of the speed of light and crushes its mammoth core down to a cinder a few kilometers in diameter.

Now, researchers have the first evidence of a souped-up supernova--an eruption of similar origin that generates 100 times more energy. Traditional supernovas often leave behind a compact kernet known as a neutron star, but this explosion may have given birth to a much denser remnant, a black hole.

On May 5, researchers at the Australia Telescope Compact Array in Narrabri detected the most intense radio emission ever recorded from a stellar explosion. The most likely explanation is that a massive star underwent an explosion so cataclysmic that material raced into space at nearly the speed of light, asserts Shrinivas R. Kulkarni of the California Institute of Technology in Pasadena. He and his colleagues describe the findings in a May 13 circular of the International Astronomical Union.

Theorists recently invoked such an explosion, dubbed a hypernova, to explain the enormous energy unleashed by a gamma-ray burst recorded in December 1997 (SN: 5/9/98, p. 292).

Intriguingly, just 10 days before the May 5 radio outburst, the Dutch-Italian satellite BeppoSAX recorded a burst of gamma rays from the same patch of sky. However, X-ray emissions recorded by BeppoSAX shortly after the gamma-ray burst do not coincide with the radio emissions Thus, it remains uncertain whether the radio emission is associated with this gamma-ray burst, notes Bohdan Paczynski of Princeton University.

The recent stellar explosion is fascinating in its own right, says Kulkarni. The visible light radiated by the exploding object, which astronomers first observed on May 2, is characteristic of a new horn supernova, lie notes, Spectni revealed that the explosion originated in it relatively nearby galaxy about 130 million light-years from Earth.

When Kulkarni's Australian collaborators recorded radio waves from the exploded object shortly afterward, it marked the first time that astronomers had detected a strong Source of radio waves from a newborn supernova, he says.

Kulkarni and his collaborators calculated the intensity of the radio wave emission, measured in terms of temperature, as about 300 trillion kelvins--100 times greater than an ordinary supernova could produce. The most reasonable explanation, he says, is that his sopcinova expelled a portion of its material at 99 percent of the speed of light.

If the discovery holds up, "it will provide the missing link between supernovas and gamma-ray bursts and it Rosetta stone for understanding both," says Stanford E. Woosley of the University of California, Santa Cruz. He argues that if supernovas mark the birth of neutron stars, then hypernovas and gamma-ray bursts may mark the birth of black holes.