[escepticos] materia oscura

[TORABE <TORABE@...>]

Hola.
He encontrado esta noticia de finales del mes pasado. En ella se habla 
del descubrimiento de una ?red? de materia oscura que contendría la 
mayor parte de matería del universo. Dada la importancia que creo 
tendría de ser cierta y la poca publicidad que se ha dado de la misma 
(he estado desconectado unos días, pero he seguido algunos 
informativos de tv y radio y no he oído nada de eso, sí me he enterado 
en cambio de la supuesta ralentización de la luz ) no sé hasta que 
punto hay que tomarla como totalmente confirmada. Algún ?experto? en 
el tema que quiera opinar?... 
Saludos.
(Este artículo lo podéis encontrar en 
http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-190.html)



NASA's Chandra X-ray Observatory has discovered part of an 
intergalactic web of hot gas and dark matter that contains most of the 
material in the universe. The hot gas, which appears to lie like a fog 
in channels carved by rivers of gravity, has been hidden from view 
since the time galaxies formed. The Marshall Center manages the 
Chandra program.
NASA?s Chandra X-ray Observatory has discovered part of an 
intergalactic web of hot gas and dark matter that contains most of the 
material in the universe.  The hot gas, which appears to lie like a 
fog in channels carved by rivers of gravity, has been hidden from view 
since the time galaxies formed.
?The Chandra observations, together with ultraviolet observations, are 
a major advance in our understanding of how the universe evolved over 
the last 10 billion years,? said Fabrizio Nicastro of the Harvard-
Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., and 
head of one of the teams of scientists involved in the discovery.
Four independent teams of scientists, whose results appear as separate 
papers in The Astrophysical Journal, used Chandra to detect 
intergalactic gas with temperatures ranging from 300,000 to 5 million 
degrees Celsius. This gas forms part of a gigantic system of hot gas 
and dark matter that defines the cosmic landscape. The gaseous 
component alone contains more material than all the stars in the 
universe.
?We had strong suspicions from the Big Bang theory and observations of 
the early universe that this gas exists in the present era, but like a 
stealth aircraft it had eluded our detection,? said Claude Canizares 
of the Massachusetts Institute of Technology (MIT), who along with 
Taotao Fang, led of one of the teams.
The hot gas detected by Chandra can be used to trace the presence of 
the more massive dark matter component.  The discovery of the hot gas 
may eventually enable astronomers to map of the distribution of dark 
matter in the universe and perhaps understand its origin.
Ultraviolet telescopes had detected cooler components of the hot gas 
system, but  because of its high temperatures most of it is detectable 
only with an extremely sensitive X-ray telescope. The various groups 
used two techniques to probe the intergalactic gas.  One method uses 
the absorbing effects of the gas on X-rays from distant galaxies.
On their way to Earth, the X-rays from a distant quasar dim as they 
pass through a cloud of the intergalactic gas.  By measuring the 
amount of dimming due to oxygen and other elements in the cloud, 
astronomers were able to estimate the temperature, density and mass of 
the absorbing gas.
Observations of the quasars PKS 2155-304 by the MIT and Harvard-
Smithsonian groups, and H1821+643 by an Ohio State group, revealed 
various parts of the hot gas system. One of these appears to be a 
filament in which the Milky Way and Andromeda galaxies are embedded, 
whereas other detected portions are at distances of a few billion 
light years from Earth.
These results confirm earlier work by Joel Bregman and Jimmy Irvin of 
the University of Michigan in Ann Arbor, who flipped the normal 
procedure, and used the fact that the hot gas is itself a source of X-
rays.  By observing the absorption of X-rays from the hot gas by a 
foreground galaxy, they were able to deduce presence of hot gas behind 
the galaxy.
?Normally the doctor studies the X-ray shadow produced by your bones 
to learn about your bones,? said Bregman.  ?In essence, we used the 
shadow to learn about the X-ray machine.? 
During the first few billion years of the universe, about 20 percent 
of the matter came together under the influence of gravity to form 
groups and clusters of galaxies. Theories predict that most of the 
remaining normal matter and dark matter formed an immense filamentary 
web connecting the groups and clusters of galaxies, predicted to be so 
hot that it would be invisible to optical, infrared, and radio 
telescopes.
?Computer simulations have been telling us for several years that most 
of the ?missing? gas in the universe should be in hot filaments,? said 
Smita Mathur, leader of the Ohio State team.  ?Most of those filaments 
are too faint to see, but it looks like we are finally finding their 
shadows.?
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the 
Chandra program, and TRW, Inc., Redondo Beach, Calif., is the prime 
contractor. The Smithsonian's Chandra X-ray Center controls science 
and flight operations from Cambridge, Mass.