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Tuesday, 7 November, 2000, 18:27 GMT
Chandra sees 'cosmic traffic pile-up'
X-ray images
An X-ray view of the core of a distant galaxy
By BBC News Online science editor Dr David Whitehouse

The Chandra X-ray Observatory has seen new details of the jet of super-hot gas shooting from the heart of a quasar.

Quasars are distant galaxies with brilliant cores, thought to be bright because of the colossal energy released when matter is sucked into a black hole.

The jet of gas expelled from quasars, often at velocities very close to the speed of light, have long puzzled scientists.

Astronomers believe the new observations of quasar 3C273, when coupled with optical and radio data, may reveal how such very high-velocity jets are driven.

To the core

"For the first time, Chandra has given us an X-ray view into the area between 3C273's core and the beginning of the jet," said Herman Marshall of the Massachusetts Institute of Technology, US.

"Instead of being void of X-ray emission, Chandra has enabled us to detect a faint, but definite, stream of energy," he added.

Most optical, radio, and earlier X-ray observations of high-powered jets has shown the material emerging in "blobs". The newly discovered, continuous X-ray emission from the core in 3C273 may show scientists what it is that provides the power for the jets.

Astronomers would like to learn why matter is violently ejected from the quasar's core, and then appears to suddenly slow down.

Jet formation

"If there is a slower car in front on a highway, a faster one from behind will eventually catch up and maybe cause a wreck," said Herman Marshall.

"If the jet flow velocity changes, then gas shocks may result, which are akin to car collisions. These gigantic clouds of high-energy electrons, now seen in X-rays by Chandra, may indeed be the result of some sort of cosmic traffic pile-up."

The energy emitted from the jet in 3C273 probably comes from gas that falls towards a supermassive black hole at the centre of the quasar, but is then redirected by strong electromagnetic fields into a jet. However, this process is still poorly understood.

While the black hole itself cannot be seen directly, properties of the hole can be deduced by studying the jet.

Perplexing properties

The quasar 3C273 is no stranger to making astronomical news.

It was first identified in the 1960s and was one of the first objects to be recognised as a "quasi-stellar" object. Its properties were very perplexing.

Only after careful consideration did astronomers determine that 3C273, and others like it, were not nearby stars, but very distant galaxies with incredibly powerful nuclei.

The core of an active galaxy, which may occupy a region of space no bigger than our Solar System, can shine with the luminosity of 20 billion Suns.

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See also:

26 May 00 | Sci/Tech
Chandra homes in on a black hole
08 Jun 00 | Sci/Tech
Bad places in space
12 Jul 00 | Sci/Tech
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