York U. team finds 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.

“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 professor Norbert
Bartel, 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
recently 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 center 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 center is unveiled. It is a text-
book story, now witnessed for the first time,” said Norbert
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 center of the shell which were noticeably
different than those of the shell and not associated with it.