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1E 0657-56: NASA Finds Direct Proof of Dark Matter
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| Credit: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al. |
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Tiff (9.2 MB) |
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This composite image shows the galaxy cluster 1E 0657-56, also known as the
"bullet cluster." This cluster was formed after the collision of two large
clusters of galaxies, the most energetic event known in the universe since
the Big Bang.
Hot gas detected by Chandra in X-rays is seen as two pink clumps in the
image and contains most of the "normal," or baryonic, matter in the two
clusters. The bullet-shaped clump on the right is the hot gas from one
cluster, which passed through the hot gas from the other larger cluster
during the collision. An optical image from Magellan and the Hubble Space
Telescope shows the galaxies in orange and white. The blue areas in this
image show where astronomers find most of the mass in the clusters. The
concentration of mass is determined using the effect of so-called
gravitational lensing, where light from the distant objects is distorted by
intervening matter. Most of the matter in the clusters (blue) is clearly
separate from the normal matter (pink), giving direct evidence that nearly
all of the matter in the clusters is dark.
The hot gas in each cluster was slowed by a drag force, similar to air
resistance, during the collision. In contrast, the dark matter was not
slowed by the impact because it does not interact directly with itself or
the gas except through gravity. Therefore, during the collision the dark
matter clumps from the two clusters moved ahead of the hot gas, producing
the separation of the dark and normal matter seen in the image. If hot gas
was the most massive component in the clusters, as proposed by alternative
theories of gravity, such an effect would not be seen. Instead, this
result shows that dark matter is required.
| Fast Facts for 1E 0657-56: |
| Credit |
X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al. |
| Scale |
Image is 7.5 x 5.4 arcmin |
| Category |
Groups & Clusters of Galaxies |
| Coordinates (J2000) |
RA 06h 58m 19.85s | Dec -55º 56' 29.40" |
| Constellation |
Carina |
| Observation Dates |
2004: Aug 10, 11, 14, 15, 17, 19, 24, 25
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| Observation Time |
140 hours |
| Obs. IDs |
5355-58, 5361, 4984-86
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| Color Code |
Energy (X-ray: Pink; Optical: White/Orange; Lensing Map: Blue) |
| Instrument |
ACIS |
| Also Known As | The Bullet Cluster |
| Distance Estimate |
About 3.8 billion light years |
| Release Date |
August 21, 2006 |
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