Found at last

Published: Thursday 15 June 2000

Some answers to one of the most embarrassing mysteries before astronomers are finally beginning to emerge. Astronomers using the Hubble space telescope have said they had discovered much of the world's missing hydrogen. They stumbled upon the answer by finding oxygen. Despite knowing how much matter should be there by the behaviour of galaxies and other bodies, so far most of the matter cannot be found in the universe or cannot be seen by them. The common belief is that most of the missing matter is 'dark matter' which is a special kind of matter that cannot be seen on earth. But a lot of the so-called baryonic matter--the regular stuff made up of protons, neutrons and electrons--also could not be accounted for. Astronomers think a lot of it is tied up in the form of highly ionised, or charged, hydrogen in between galaxies. Researchers Todd Tripp of Princeton University, Blair Savage from the University of Wisconsin at Madison and colleagues used the orbiting Hubble space telescope to look for it - not by looking directly, because hot hydrogen is extremely hard to see, but by looking for ionised oxygen.

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