This Echo is READ ONLY !   NO Un-Authorized Messages Please!
 ~~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Research Communications
Ohio State University

Contact:
Smita Mathur, (614) 292-5779; Mathur.17{at}osu.edu

Written by Pam Frost Gorder
(614) 292-9475; Gorder.1{at}osu.edu

Embargoed for release until 2:00 p.m. EST, February 12,
2003, to coincide with publication in the journal Nature.

RIVERS OF GAS COULD PROVIDE PART OF UNIVERSE'S "MISSING" MATTER
===============================================================

COLUMBUS, Ohio -- An Ohio State University astronomer and her 
colleagues have detected a type of hot gas in space that could account 
for part of the "missing" matter in the universe.

A gas cloud, one trillion times more massive than our sun and more 
than 150 times hotter, surrounds our local group of galaxies, the 
astronomers reported in the journal Nature.

Though vast, this gas cloud is only part of larger rivers of gas that 
wind between all the galaxies of the universe, said Smita Mathur, 
associate professor of astronomy at Ohio State.

Scientists believe that after the Big Bang, only 20 percent of the 
"normal" material in the early universe -- such as protons and 
neutrons -- converged to form stars and galaxies as seen in the night 
sky. The remaining 80 percent of this normal matter, which astronomers 
refer to as baryons, hasn't been accounted for.

A related mystery concerns dark matter, unseen material that is 
believed to provide most of the gravity in the universe.

Mathur said that astronomers aren't sure what dark matter is made of, 
but that baryons can be used as a marker to find it.

"We believe baryons are drawn to the gravity of the dark matter, so 
they trace the location of dark matter through space," Mathur said. 
"One provides a map to the other."

Mathur collaborated with lead author Fabrizio Nicastro and his 
colleagues at the Harvard-Smithsonian Center for Astrophysics, 
including Andreas Zezas, Martin Elvis, Cesare Cecchi-Pestellini, 
Douglas Burke, Jeremy Drake, and Piergiorgio Casella; and Fabrizio 
Fiorre of the Astronomical Observatory of Rome.

Last summer, Mathur and her colleagues announced preliminary evidence 
of baryonic gas found with NASA's Chandra X-ray Observatory. In 
Nature, they now report definitive evidence of the gas taken with 
NASA's Far Ultraviolet Spectroscopic Explorer (FUSE).

"This gas is so hot that it radiates at energies too high to be seen 
at visible wavelengths, so we had to look at it in the ultraviolet," 
Mathur explained.  They examined the gas surrounding the Milky Way and
Andromeda galaxies, part of our local group of galaxies.

The high temperature explains why so many baryons are invisible today. 
At some point after the Big Bang, the baryons collided and ignited in 
a "heat shock" that created so much energy as to render the particles
invisible.

But the finding doesn't answer questions about the composition of dark 
matter. Some scientists have hypothesized that dark matter is made up 
of dim stars and large gas planets similar to our Jupiter; others
believe it is made of tiny but massive particles.

"Either is still a possibility," Mathur said.

She and her collaborators would hope to probe the gas again with 
Chandra, to perform the same kind of in-depth analysis they did with 
FUSE.

This research was partly supported by NASA-Chandra grants and a 
NASA-Chandra X-ray Center contract.

-END OF FILE-
=============

---