The return of regular missing mass

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In recent years, astronomers have learned more about the composition of our Universe: 70% of dark energy, dark matter 25% (both equally mysterious) and about 5% ordinary matter.

According to the standard cosmological model, the total number of elementary particles that make up the ordinary matter (baryons such as protons and neutrons) has remained constant since the
Big Bang. Or baryons detected in the nearby Universe are half as many as those of the Big Bang universe. To account for the missing half, the theory therefore provides for the existence of what is called the WHIM (Warm-Hot Intergalactic Medium), an intergalactic web of hot, diffuse gas. Continuing published work two years ago by four teams of astronomers, Fabrizio Nicastro of the Harvard-Smithsonian Center for Astrophysics, and colleagues studied the absorption spectrum of the quasar Markarian 421, from the Observatory data Chandra X-ray emission and observations in the ultraviolet. they have
discovered the presence of ions (carbon, nitrogen, oxygen and neon) in two gas clouds heated to nearly a million degrees Celsius crossed by the quasar. Extrapolating to the whole universe the size of these representatives of the WHIM located 150 and 370 million light years from Earth, the scientists were able to estimate accurately the density of baryons contained in this type of environment .

And this estimate is the missing mass. New instruments may be needed to complete the research. It was envisaged to install a spectrograph on Hubble
but the uncertain future of the telescope now jeopardizes the project.

NYT 08 / 02 / 05 (Recovering Lost Atoms of cosmos)


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