These composite images, taken by two different teams using the Hubble Space Telescope, show different results concerning the amount of dark matter in the core of the merging galaxy cluster Abell 520.
Dark matter is an invisible form of matter that astronomers deduce is the underlying gravitational "glue" that holds galaxies together.
Top Image: Observations of the cluster, taken by D. Clowe with the Advanced Camera for Surveys, map the amount of dark matter in Abell 520. The map reveals an amount of dark matter astronomers expect based on the number of galaxies in the core. The dark-matter densities are marked in blue, and the dotted circle marks the dark-matter core. The map is superimposed onto visible-light images of the cluster.
Bottom Image: A second team, led by James Jee of the University of California, Davis, used the Wide Field Planetary Camera 2 and found an unusual overabundance of dark matter in the cluster's core, denoted by the bright blue color at image center. The observation was surprising because astronomers expect that dark matter and galaxies should be anchored together, even during a collision between galaxy clusters.
This discrepancy between the two results requires further observation and analysis, say researchers.
The two dark-matter maps were made by detecting how light from distant objects is distorted by the galaxy clusters, an effect called gravitational lensing.
Abell 520 is located 2.4 billion light-years away.
Credits
[Top] NASA, ESA, and D. Clowe, (Ohio University);[Bottom] NASA, ESA, and J. Jee (University of California, Davis)
| About The Object | |
|---|---|
| Object Name | Abell 520 |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
