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Wednesday, November 17, 1999 Published at 15:53 GMT


X-rays mark galactic collision

Enough super hot gas to make hundreds of normal galaxies

By BBC News Online Science Editor Dr David Whitehouse

This image of the distant galaxy 3C295 shows a titanic explosion surrounded by a vast cloud of gas at a temperature of fifty million degrees. It was taken by the Chandra X-ray telescope which orbits Earth from space.

The gas cloud is visible only by the high energy radiation it emits. It has more than a hundred galaxies embedded in it, as well as enough matter to make a thousand more. The galaxies are too cool to be visible in X-rays.

[ image: Radio observations reveal clouds ejected from the vicinity of a black hole]
Radio observations reveal clouds ejected from the vicinity of a black hole
The superhot gas cloud, roughly two million light years in diameter, is among the most massive objects in the Universe.

It is so distant that we see it as it was five billion years ago. Astronomers think that it has grown over the aeons as mass from a colossal gas cloud cooled and settled onto the galaxy.

The evidence suggests that the centre of 3C295 was wracked by an awesome explosion about a million years before the current view. The bright X-ray knots, seen for the first time in this Chandra image, are probably the result of the dumping of gas onto 3C295.

Supermassive black hole

The central knot coincides with the centre of the galaxy. These X-rays are most likely due to matter falling into a supermassive black hole.

The upper and lower knots are in the same location as two large lobes of radio emission. The distance from the top to the bottom knot is about 100,000 light years, comparable to the diameter of our Milky Way galaxy.

Astronomers estimate that the total X-ray power in the knots is three times greater than all the power produced by our galaxy.

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