Washington, May 21 : Astronomers have claimed to have found baryons, which is half of the missing normal matter of the universe, in the spaces between the galaxies.
Although the universe contains billions of galaxies, only a small amount of its matter is locked up in them. Thus, scientists have determined over the years that most of the universe's matter that was created during and just after the Big Bang must be found elsewhere.
Now, in an extensive search of the local universe using the Hubble Space Telescope, astronomers claim to have found about half of the missing normal matter in the spaces between the galaxies.
Known as baryons, this missing matter consists of protons, neutrons, and other subatomic particles that make up ordinary matter such as hydrogen, helium, and heavier elements. Baryonic matter forms stars, planets, moons, and even the interstellar gas and dust from which new stars are born.
This important component of the universe is known as the "intergalactic medium," or IGM, and it extends essentially throughout all of space, from just outside our Milky Way galaxy to the most distant regions of space observed by astronomers.
"We think we are seeing the strands of a web-like structure that forms the backbone of the universe," said Mike Shull of the University of Colorado.
"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," he added.
Danforth and Shull, of the Department of Astrophysical and Planetary Sciences at the University of Colorado in Boulder, looked for the missing baryonic matter by using the light from distant quasars to probe spider-web-like structure that permeates the seemingly invisible space between galaxies.
The bright quasar light was measured to penetrate more than 650 filaments of hydrogen in the cosmic web. Eighty-three filaments were found laced with highly ionized oxygen in which five electrons have been stripped away.
The presence of highly ionized oxygen (and other elements) between the galaxies is believed to trace large quantities of invisible, hot, ionized hydrogen in the universe.
The team also found that about 20 percent of the baryons reside in the voids between the web-like filaments. Within these voids could be faint dwarf galaxies or wisps of matter that could turn into stars and galaxies in billions of years.
"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," said Shull. "Studying the cosmic web gives us information on how galaxies built up over time," he added.