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Fraser
2003-Jul-25, 09:44 PM
SUMMARY: Two Canadian and a US astronomer have created a detailed map of the halo of dark matter that seems to surround all galaxies. The mass of dark matter accounts for 50 times the mass and five times the size of the light-producing material in a galaxy. This flattened sphere-shaped halo was seen by measuring how the gravity from a closer galaxy bends the light from a distant object that passes behind it; a technique called gravity lensing.


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Hadrian
2003-Jul-26, 01:54 PM
I once remember a scientist stating that those stars at the edge of a galaxy were unaffected by its central gravity. This was not so long ago, and at that time I had thought how strange this comment was, after all, if the overall gravity of a galaxy had no effect on its outer rim, then the edges of galaxies would be ragged and falling apart.
This dark matter halo that has been discovered surrounding galaxies is not therefore as strange as it seems. Perhaps even produced by the black hole at the center of a galaxy, all the stars and other matter are drawn and captured within it like moths drawn to a flame.
There is so much we do not know about Black Holes.
That they hold galaxies together is now almost certain, yet we have no full understanding of their true nature.
It is even possible that within a galaxy, within the energetic mix of its trillions of stars, this energy is all but impossible to detect, and therefore can only be seen across vast distances of space, surrounding faraway galaxies.