More Images of Dark Energy
1
Images of Galaxy Clusters in Dark Energy Study
These six galaxy clusters from the Chandra X-ray
Observatory are representative of over 80 clusters that
were used to track the effects of dark energy on these massive objects
over time. Most of the matter in galaxy clusters is in the form of
very hot gas, which emits copious amounts of X-rays. By studying
clusters across large distances, astronomers have determined that dark
energy has stifled their growth.
(Credit: NASA/CXC/SAO/A.Vikhlinin et al.)
2
Simulation Showing Structures Growing with Cosmic Time
These are three snapshots taken from a simulation by J.Diemand, J.Stadel
and B.Moore showing the formation of cosmic structure in the presence of
dark matter and dark energy. The snapshots are taken at times when the
Universe was 20%, 60% and 100% of its full size (for ease of comparison,
the images have been scaled to be the same size). Note how structures
increase in size under the attractive force of gravity, leading to the
formation of the largest collapsed structures, galaxy clusters. The growth
of galaxy clusters is stifled at later times by dark energy, which is
driving accelerated expansion.
(Credit: J.Diemand et al.)
3
Images of Abell 85
This one galaxy cluster is representative of over 80 clusters that
were used to track the effects of dark energy on these massive objects
over time. This galaxy cluster, Abell
85, is shown in X-ray light from NASA's Chandra X-ray
Observatory and optical light from SDSS. Most of the matter in galaxy clusters is in the form of
very hot gas, which emits copious amounts of X-rays. By studying
clusters across large distances, astronomers have determined that dark
energy has stifled their growth.
Credits: X-ray(NASA/CXC/SAO/A.Vikhlinin et al.); Optical (SDSS)
4
Comparing of Expansion of Universe and Growth of Structures
This pair of illustrations shows the change in scale of the Universe
over cosmic time, followed by the change in the weight of a typical
galaxy cluster over the same time frame. The orange line shows the
evolution of the observed Universe, with dark energy and cosmic
acceleration, and the yellow and blue lines show high and low density
models that do not contain dark energy. The observed change in weight
of galaxy clusters over the last 7 billion years agrees very well with
predictions for a Universe dominated by dark energy.
(Illustration: NASA/CXC/M.Weiss)
5
Illustration of the Universe's Composition
As shown in this illustration, dark energy is estimated to contribute
about 74% of the energy in the Universe, dark matter about 22% and
normal matter about 4%. Only the normal matter can be directly
detected with telescopes, which includes the hot gas emitted by galaxy
clusters. Scientists have used this information from normal matter to
get a better handle on the properties of dark energy.
(Illustration: NASA/CXC/M.Weiss)
6
"Weighing" the Universe with Chandra
This set of three illustrations gives a basic explanation of how galaxy
cluster observations using Chandra can be used to study dark energy. The
analogy used here is that of measuring scales. The measured weight of
clusters is shown on the left side of the scales, while different parts of
the theory, including the amount of matter, the amount of dark energy and
properties of dark energy, are put on the other side of the scales until
there is a balance. Other important factors are the current expansion rate
of the Universe (Hubble constant) and the clumpiness of matter in the early
Universe (amplitude). This is how it is possible to "weigh" the universe
using galaxy clusters.
(Credit: A.Vikhlinin)
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