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Thursday, 8 June, 2000, 13:51 GMT 14:51 UK
Bad places in space
Nasa
Cosmic crossbow: The remnant of an exploded star
By BBC News Online science editor Dr David Whitehouse

Stunning images of the hot and violent parts of the cosmos have been revealed at an astronomy conference in the US.

Nasa
Chandra being deployed from the space shuttle
Jets of hot gas pushing their way through space from a black hole, streams of X-rays blasting clouds of gas in a turbulent galaxy and a superdense star throwing charged particles into space like a cosmic catherine wheel were shown to impressed scientists.

The images were taken by the Chandra X-ray Observatory launched from the space shuttle last year.

X-rays come from hot gas so Chandra homes in on cosmic violence such as exploded stars and matter being sucked into a black hole.

Cosmic crossbow

In one of its most remarkable images, Chandra has seen details of a gas cloud that resembles a gigantic cosmic crossbow.


Nasa
X-ray shadows and radiation in the Perseus galaxy
The gas cloud, part of the wreckage of an exploded star called the Vela supernova remnant, is formed by a pulsar, a rapidly rotating superdense neutron star that spins out rings and jets of high energy particles.

"What is fascinating is that the jets from the pulsar are directed exactly along the direction of the pulsar's motion," said Dr George Pavlov of Penn State University, speaking at the 196th national meeting of the American Astronomical Society (AAS).

"The southern jet looks like a rocket exhaust!"


Nasa
The Pictor X-ray jet streaks across space
Astronomers can trace the X-ray jet all the way into the neutron star. A strange inner ring can be seen for the first time. It is thought to be a shock wave caused by matter rushing away from the neutron star.

The neutron star is enveloped in a cloud of high-energy particles emitting X-rays as they spiral around magnetic field lines. This cloud is embedded in a much larger cloud produced by the supernova and has a swept-back shape because of its motion through the larger cloud.

Galactic cannibal

Chandra has also observed the supergiant galaxy Perseus A, showing how that galaxy has grown by cannibalising gas and other galaxies in its vicinity.


Nasa
X-rays from the violence of a black hole in NGC 4151
For the first time, astronomers can see an X-ray shadow cast by a smaller galaxy as its gas is stripped away by the enormous central galaxy.

Over the eons, Perseus A has accumulated hundreds of billions of stars to become one of the most massive known galaxies.

Black hole

Also revealed at the AAS meeting was the X-ray observatory's image of a spectacular luminous spike of X rays coming from the vicinity of a giant black hole in the centre of the galaxy Pictor A.

The spike, or jet, is a beam of particles that streaks across hundreds of thousands of light years of intergalactic space toward a brilliant X-ray hot spot that marks its end point.

"Both the brightness and the spectrum of the X rays are very different from what theory predicts," said Professor Andrew Wilson of the University of Maryland.

"The Chandra observations are telling us that something out there is producing many more high energy particles than we expected," he said.

The hot spot has been seen with optical and radio telescopes. Radio telescopes have also observed a faint jet.

Cosmic disruption

Another observation shows the disruptive effects that a massive black hole can have over thousands of light years.

The activity in galaxy designated NGC4151 is believed to be due to a giant black hole in the nucleus with an estimated mass 10 million times that of the Sun. As matter swirls toward the black hole, it releases a prodigious amount of energy, much of it as X-rays.

"The black hole is shining an X-ray searchlight which illuminates the clouds in the night sky of NGC 4151," said Dr Patrick Ogle of the Massachusetts Institute of Technology.

"The clouds are being thoroughly cooked by the powerful beam from the black hole," said Ogle.

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See also:

23 Jul 99 | Sci/Tech
Shuttle deploys X-ray observatory
27 Aug 99 | Sci/Tech
Impressive debut for Chandra
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