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Dark Matter Illustrations
Dark matter is a term used to describe the mass in galaxies and clusters of galaxies. The existence of dark matter is inferred from its gravitational effects, but it has not been detected by electromagnetic radiation.
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1. What the Universe is Made of
Most of the Universe is dark. The protons, neutrons and electrons that make up the stars, planets and us represent only a small fraction of the mass and energy of the Universe. The rest is dark and mysterious. X-rays can help reveal the secrets of this darkness. X-ray astrophysics is crucial to our understanding not only of the Universe we see, but the quest to determine the physics of everything.
(Credit: NASA/CXC/M.Weiss)

Chronicle Article: The Universe

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2. X-ray Distance Measurement Technique
This set of illustrations shows the technique used to make distance measurements to galaxy clusters. Chandra's observations are used to determine the ratio of the mass of the hot gas and the mass of the dark matter in different galaxy clusters. This "gas fraction" depends on the assumed distances to the clusters, which in turn depends on the amount of matter and dark energy in the Universe. Because galaxy clusters are extremely large, the gas fraction should be the same for every cluster, and so the distances to the clusters are adjusted to satisfy this requirement. Each of these 3 illustration shows Chandra in the top left, observing a galaxy cluster, shown in the top right (in red). The relative amounts of hot gas (in red) and dark matter (in blue) are shown at the bottom, with the green marker giving the expected, correct amount. The first illustration shows a gas fraction that is too small, implying that the distance to the cluster is too small, the second shows the correct gas fraction and distance, and the third illustration shows a gas fraction and distance that are too large. (Credit: NASA/CXC/M.Weiss)

View X-ray Distance Measurement Technique animation

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3. Energy Distribution of the Universe
The new Chandra observations include estimates of the total energy content of the Universe. As shown in this illustration, dark energy is estimated to contribute about 75% of the energy in the Universe, dark matter about 21% and normal matter about 4%. Only the normal matter can be directly detected with telescopes, and about 85% of this is hot, intergalactic gas, as detected in Chandra observations of galaxy clusters. (Credit: NASA/CXC/M.Weiss)


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Chronicle Article: The Wonderful (And Fearful) Dark Side
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4. Three Possible Futures for the Universe
This illustration shows three possible futures for the Universe, depending on the behavior of dark energy, by showing how the scale of the Universe may change with time. If dark energy is constant, as the new Chandra results suggest, the expansion should continue accelerating forever. If dark energy increases, the acceleration may happen so quickly that galaxies, stars, and eventually atoms will be torn apart, in the so-called Big Rip. Dark energy may also lead to a recollapse of the Universe, in the Big Crunch. The illustration also shows the early decelerating expansion of the Universe, followed by the accelerating phase that started about 6 billion years ago. (Credit: NASA/CXC/M.Weiss)

Photo Album: Galaxy Clusters and Dark Energy
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5. Animation Stills: Effects of Dark Energy
These still images show the expansion history of the Universe by modeling the Universe as a two-dimensional grid of galaxies. The Big Bang, shown as a flash of light, is immediately followed by rapid expansion of the Universe. This expansion then slows down because of the gravitational attraction of the matter in the Universe. As the Universe expands, the repulsive effects of dark energy become important, causing the expansion to accelerate. (Credit: NASA/STScI/G. Bacon)

View Animation of the Effects of Dark Energy
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6. Dark Matter
X-ray telescopes have discovered vast clouds of multimillion degree gas in clusters of galaxies. An X-ray image has been superimposed on an optical picture of a cluster of galaxies. This image was taken by ROSAT and shows hot gas highlighted in false red color. (Illustration: Richard Mushotzky(GSFC/NASA),ROSAT,ESA,NASA)

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7. Still Image from Dark Matter Animation
Clues from Chandra have enabled scientists to constrain the size of dark matter particles in galaxy clusters. Dark matter is the invisible and unknown material that constitutes about 80% of the matter in the Universe. (Credit: NASA/SAO/CXC)

Related Field Guide
Animations & Video: Dark Matter
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