York researchers find evidence of new black hole or neutron star

Researchers at York University have announced the discovery of what they believe is a brand new black hole or neutron star. The object, which was detected as radio waves coming from the centre of a supernova in a nearby galaxy, appears to confirm the theory that stars more than five times the mass of Earth’s sun leave behind new objects after they explode.

Left and below: Artist’s impressions of Supernova 1986J.  N. Bartel & M. Bietenholz; artist: G. Arguner

“This is very exciting,” said Michael Bietenholz, senior research associate in the Department of Physics and Astronomy at York, “because this would be the first direct link between a modern supernova and a black hole or a neutron star. We just don’t know yet if it is one or the other. It’s like witnessing the birth of a baby for the first time and not yet knowing if it’s a boy or a girl.” The team of astronomers includes York’s Norbert Bartel, a professor in the Faculty of Pure and Applied Science and one of the world’s foremost authorities on supernovae, and Michael Rupen of the National Radio Astronomy Observatory in Socorro, New Mexico.

The article describing the observations was published yesterday in the journal Science. Bietenholz will talk about the discovery next week at a meeting of the Canadian Astronomy Society in Winnipeg and present the team’s findings at a conference in Paris in July.

Although scientists have long believed black holes and neutron stars are formed as older stars die and become supernova, this is the first time the phenomenon has been observed directly. Bietenholz said signs of the new object were not detected in previous studies of Supernova 1986J, which occurred only 20 years ago at the relatively close distance of 30 million light years from Earth.

A supernova is the explosion of a star’s outer shell that occurs when its core burns out and collapses onto itself. When a supernova explodes, the outer layers of the original star are violently thrown off, and the resulting shell of gas expands with velocities of 10,000 to 20,000 km/sec. The core of the original star, at the centre of the explosion, is thought to collapse into a neutron star or a black hole, which remains behind. Until now, no black hole had been detected in any supernova, and neutron stars had been detected only in historical supernovae several centuries or even millennia old.

“A supernova is likely the most energetic single event in the universe after the big bang. It is just fascinating to see how the smoke from the explosion is blown away and how now after all these years the fiery centre is unveiled. It is a textbook story, now witnessed for the first time,” said Bartel.

When supernovae explode they disperse into space most of the elements needed to form Earth-like planets and life forms, including humans. Without supernovae, all planets would be gaseous like Jupiter, and life on Earth could not have evolved.

Using a network of radio telescopes from around the world, the team made images of Supernova 1986J, which exploded in the nearby galaxy NGC 891. Earlier radio images showed the supernova’s expanding shell gas but no other objects. In new images made in June 2003, the team detected radio waves in the centre of the shell which were noticeably different from those of the shell and not associated with it.

Copies of the Science paper are available from the AAAS Office of Public Programs, 202-326-6440, or by e-mail to scipak@aaas.org.