This composite image shows the massive galaxy cluster MACS J0717.5+3745 (MACS J0717, for short), where four separate galaxy clusters have been involved in a collision – the first time such a phenomenon has been documented. Hot gas is shown in an image from NASA's Chandra X-ray Observatory, and galaxies are shown in an optical image from NASA's Hubble Space Telescope. The hot gas is color-coded to show temperature, where the coolest gas is reddish purple, the hottest gas is blue, and the temperatures in between are purple.
The repeated collisions in MACS J0717 are caused by a 13-million-light-year-long stream of galaxies, gas, and dark matter – known as a filament – pouring into a region already full of matter. A collision between the gas in two or more clusters causes the hot gas to slow down. However, the massive and compact galaxies do not slow down as much as the gas does, and so move ahead of it. Therefore, the speed and direction of each cluster's motion – perpendicular to the line of sight – can be estimated by studying the offset between the average position of the galaxies and the peak in the hot gas.
MACS J0717 is located about 5.4 billion light-years from Earth. It is one of the most complex galaxy clusters ever seen. Other well-known clusters, like the Bullet Cluster and MACS J0025.4-1222, involve the collision of only two galaxy clusters and show much simpler geometry.
Credits
NASA, ESA, CXC, C. Ma, H. Ebeling, and E. Barrett (University of Hawaii/IfA), et al., and STScI| About The Object | |
|---|---|
| Object Name | MACS J0717.5+3745 |
| Object Description | Cluster of Galaxies |
| R.A. Position | 07h 17m 33.79s |
| Dec. Position | 37° 45' 20.01" |
| Constellation | Auriga |
| Distance | 5.4 billion light-years or 1.7 billion parsecs |
| Dimensions | The image is roughly 4.5 arcminutes (7.7 million light-years or 2.4 megaparsecs) wide. |
| About The Data | |
| Data Description | Chandra Data: Chandra data used were from proposal . Hubble Data: The Hubble images were created from HST data from proposal : PI: Dr. H. Ebeling (University of Hawaii), I. Smail (University of Durham, UK), J.-P. Kneib (Laboratoire d'Astrophysique de Marseille, France), G. Smith (University of Birmingham, UK), and D. Donovan and E. Barrett (University of Hawaii). |
| Instrument | CXO>ACIS and HST>ACS/WFC |
| Exposure Dates | January 10, 2003 (CXO) and January 24, 2005 - February 9, 2005 (HST) |
| Filters | ACS: F606W (V) and F814W (I) ACIS Energies: 5 - 25 T(keV) |
| About The Image | |
| Color Info | The image is a composite of separate exposures made by the ACS instrument on the Hubble Space Telescope and the ACIS instrument onboard the Chandra X-ray Observatory. Two filters were used to sample broad wavelength ranges. A continuous energy band was used to sample the X-ray data. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Cyan: F606W (V) Yellow: F814W (I) Blue - Violet (temperature map): 5 - 25 T(keV) |
| 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. |
