New Image Reveals Violent Collision of Galaxies

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Astronomers at the National Radio Astronomy Observatory (NRAO) have compiled data from a variety of instruments to create a stunning composite image of colliding galaxy clusters collectively known as MACS J0717, 5.4 billion light years away in the Auriga constellation. The composite makes this the most well-studied galaxy cluster, and the image was presented at the 224th Meeting of the American Astronomical Society.

The background of the image was taken by NASA’s Hubble Space Telescope and captures wavelength spectra spanning near ultraviolet, visible, and near infrared. The blue light represents x-ray wavelengths, taken by the Chandra X-Ray Observatory. Radio waves are shown in red, and were produced by NRAO’s Very Large Array.

The blue and red regions represent some of the most sensitive images ever collected by these instruments, and the radio waves revealed results that were quite telling. The linear red region with a light-colored dot in the middle is actually a black hole with jets of particles being shot out in either direction. The irregular red region in the lower left corner is believed to be a radio galaxy being drawn into this violent cluster of collisions. The misshapen red region is the most exciting, as it is believed to indicate particles that interact with magnetic fields during the collisions, with radio waves being emitted as a byproduct.

“The complex shape of this region is unique; we’ve never spotted anything like this before,” astrophysicist Reinout van Weeren of the Harvard-Smithsonian Center for Astrophysics told NRAO. “The shape probably is the result of the multiple ongoing collisions.” 

MACS J0717 is one of the most massive known galaxy clusters, making it a popular target for astronomers. Its size and distance also makes it the largest known gravitational lens, which can bend light around it and is very useful when studying more distant celestial bodies as well as dark matter.

MACS J0717’s lensing power will also be utilized by the Frontier Fields mission for the Hubble Space Telescope. It will image the area in both visible and near infrared wavelengths. Imaging will occur twice, first in September-November of this year and again in February-May of 2015. This will allow Hubble’s cameras to collect data from the galaxy cluster fiend and adjacent parallel field, observing the most distant regions of space to date.

Colliding galaxy clusters MACS J0717+3745, more than 5 billion light-years from Earth. Background is Hubble Space Telescope image; blue is X-ray image from Chandra, and red is VLA radio image. Image credit: Van Weeren, et al.; Bill Saxton, NRAO/AUI/NSF; NASA.

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