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Hot Intergalactic Gas:
Chandra Discovers "Rivers Of Gravity" That Define
Cosmic Landscape
Four independent teams of scientists have detected
intergalactic gas with temperatures in the range
300,000 to 5 million degrees Celsius by observing
quasars with the Chandra X-ray Observatory. An
artist's rendering illustrates how 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 - see the
spectrum of the quasar PKS 2155-304 in the inset -
astronomers were able to estimate the temperature,
density and mass of the absorbing gas cloud.
Observations of PKS 2155 and the quasar 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.
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. It is thought
that this gas forms part of a gigantic system, or web,
of hot gas and dark matter that defines the cosmic
landscape. The hot gas part of this system could
contain more material than all the stars in the
universe. Ultraviolet telescopes had detected cooler
components of the hot gas system, but most of it is now
known to be detectable only with an extremely sensitive
X-ray telescope.
The hot gas detected by Chandra can be used to trace
the more massive dark matter component. Eventually,
astronomers will be able to use the hot gas to map of
the distribution of dark matter in the universe and
perhaps understand its origin.
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Fast Facts for PKS
2155-304:
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Credit
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Illustration: SAO/CXC/A.Hobart
Spectrum: NASA/MIT/T.Fang et al.
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Category
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Cosmology/Deep
Fields/X-ray Background
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Coordinates
(J2000)
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RA 21h 58m 52s | Dec -30º 13'
32" |
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Constellation
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Piscis Austrinus
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Observation
Date
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May 31, 2001 & December 6, 2001
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Observation
Time
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7.4 hours & 8.3 hours
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Obs.
ID
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1703 & 2335
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Release Date
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July 31, 2002
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Instrument
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ACIS
/LETG |
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Distance
Estimate
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Gas cloud illustrated: about 800
million light years.
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