May 21, 2008 -- Researchers say they have found about half of the universe's missing matter hidden in the spaces between billions of galaxies thanks to the Hubble telescope.
This normal matter, which is called baryons, was created during and after the Big Bang, and should not be confused with dark matter, researchers said.
"We think we are seeing the strands of a web-like structure that forms the backbone of the universe," said astronomer Mike Shull of the University of Colorado after an extensive search of the local universe.
"What we are confirming in detail is that intergalactic space, which intuitively might seem to be empty, is in fact the reservoir for most of the normal, baryonic matter in the universe."
The research, published in Tuesday's Astrophysical Journal, sought to answer the question of where the missing local normal matter had gone and what its properties are.
The analysis is the most detailed observation to date of such matter and how it looks within about four billion light-years of Earth.
Researchers used the light from 28 qasars, the brilliant hearts of distant galaxies which still have a black hole at their center, in order to illuminate these structures, a bit like torches shining on fog.
Using the space telescope imaging spectograph on board the Hubble and NASA's far ultraviolet spectroscopic explorer (FUSE), they found hot gas and spectral "fingerprints" of intervening oxygen and hydrogen superimposed on the light from the qasars.
Probing this cosmic web of normal matter will be a task taken on by the new Cosmic Origins Spectograph (COS), due to be installed on the Hubble later this year.
"We predict that COS will find considerably more of the missing baryonic matter," said Shull.
"Our goal is to confirm the existence of the cosmic web by mapping its structure, measuring the amount of heavy metals found in it, and measuring its temperature. Studying the cosmic web gives us information on how galaxies built up over time."
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