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Researchers at York University have discovered what they believe to be a newly formed black hole or neutron star, a finding that establishes a direct link between the stellar objects and supernovae — exploding stars that help form Earth-like planets and life forms, including humans.

The object, detected in a nearby galaxy called NGC891, appears to confirm the theory that large stars at least eight times the mass of Earth's sun leave behind new objects after they explode.

Scientists have long believed that black holes and neutron stars are formed as stars age and become supernovae, but this is the first time the phenomenon has been observed directly.

The findings were published Thursday in the journal Science.

“I'm quite excited about this discovery because it is what I feel is a textbook story that we can witness now for the first time,” said York University professor Norbert Bartel, an expert on supernovae who was part of the research team.

“The missing piece was always, ‘What is in the centre itself?' Theory says that ... if a massive star explodes with a mass 10 to 30 times larger than our sun, then we should see ... in the centre a neutron star or even a black hole.”

A supernova occurs when a star's core runs out of fuel and collapses onto itself, causing an explosion.

The outer layers of the star are then violently ejected, with the resulting shock wave of gas expanding at 10,000 to 20,000 kilometres a second.

This fills nearby space with elements like oxygen, iron and nitrogen that are essential to the formation of planets and life.

The core of the original star, at the centre of the explosion, is believed to collapse into a neutron star or a black hole.

“It is basically exactly what we expected but have never witnessed,” Dr. Bartel said. “It comes out from calculations and from other observations where we have here a part of the puzzle and there a part of the puzzle.... But now we actually put it together and we see the whole thing.”

Michael Bietenholz, another York University professor on the team, said more research is being done to determine if the object is a neutron star or black hole.

“We just don't know yet if it is one or the other,” he said. “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.”

A neutron star is an incredibly dense star, its entire mass condensed into a fraction of its original size.

“If you take the whole sun and compress it to the size of Toronto, then you would basically have a neutron star,” Dr. Bartel said. “That is how dense the material is packed. So one spoonful of material would have the weight of a whole aircraft carrier.”

A neutron star can sometimes collapse into a black hole, which deforms space-time around it so that everything in its vicinity is swallowed — even light.

“A black hole is more bizarre,” Dr. Bartel said. “There the material is compressed to an infinite density, so that's only theoretically calculable.”

Dr. Bietenholz said signs of the new object were not detected in previous studies of Supernova 1986J, which took place 20 years ago when it was 30 million light-years from Earth — relatively close in cosmic terms.

A light-year is the distance that light can travel in one year — about 9.5 trillion kilometres.

In June 2003, the team made new images and detected radio waves that seemed to indicate a new object in the centre of the supernova.

Until now, no black hole had been detected in any supernova, and neutron stars had been detected only in supernovae hundreds or thousands of years old.

Dr. Bietenholz said Earth's sun isn't big enough to go supernova — it will instead shrink to a dense white dwarf in about five billion years.

He 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.

The team of researchers also includes Michael Rupen of the National Radio Astronomy Observatory in Socorro, N.M.