These four dwarf galaxies are part of a census of small galaxies in the tumultuous heart of the nearby Perseus galaxy cluster.
The galaxies appear smooth and symmetrical, suggesting that they have not been tidally disrupted by the pull of gravity in the dense cluster environment. Larger galaxies around them, however, are being ripped apart by the gravitational tug of other galaxies.
The images, taken by NASA's Hubble Space Telescope, are evidence that the undisturbed galaxies are enshrouded by a "cushion" of dark matter, which protects them from their rough-and-tumble neighborhood.
Dark matter is an invisible form of matter that accounts for most of the universe's mass. Astronomers have deduced the existence of dark matter by observing its gravitational influence on normal matter, consisting of stars, gas, and dust.
Observations by Hubble's Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 million light-years away and one of the closest galaxy clusters to Earth. Of those galaxies, 17 are new discoveries.
The images were taken in 2005.
Credits
NASA, ESA, and C. Conselice and S. Penny (University of Nottingham)| About The Object | |
|---|---|
| Object Description | Dwarf Galaxies |
| Constellation | Perseus |
| Distance | 250 million light-years (77 megaparsecs) |
| Dimensions | Each individual galaxy image is 25 arcseconds (30,000 light-years or 9,200 parsecs) wide. |
| About The Data | |
| Data Description | This image was created from HST data from proposal : C. Conselice (University of Nottingham, U.K.), S. De Rijcke (University of Ghent, Belgium), and E. Held (Astronomical Observatory of Padua, Italy). The science team comprises: S. Penny and C. Conselice (University of Nottingham, U.K.), S. De Rijcke (University of Ghent, Belgium), and E. Held (Astronomical Observatory of Padua, Italy). |
| Instrument | HST>ACS/WFC |
| Exposure Dates | January and February 2005, Exposure Time: 13 hours |
| Filters | F814W (I) and F555W (V) |
| About The Image | |
| Color Info | The image is a composite of separate exposures made by the ACS instrument on the Hubble Space Telescope. Two filters were used to sample broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Yellow: F814W (I) Blue: F555W (V) |
| Compass Image |  |
| 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. |
