Kicking in the Void

NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)

A translucent leg kicks out at an orange ball in this combined image of merging galaxy cluster Abell 520 from NASA’s Hubble Space Telescope, Chandra X-ray Observatory and the Canada-France Hawaii Telescope.

Explore the false-color hues imposed on the faraway galaxies. What stories or patterns do you see? Leave a note below.

This is not a true image. Astronomers used Chandra and the CFHT telescope to map the ghostly orange and blue-green blobs of color. These colors show areas of different temperatures of hot gas and give an indication of where dark matter lies. A Hubble image was then placed within the image to give astronomers an idea of the galaxies involved in the collision.

First hypothesized about 80 years ago, dark matter is an unseen force in the Universe. Astronomers don’t know much about dark matter. The bizarre material is not made up of the same matter that makes up stars, planets and humans. But even though it is poorly understood, astronomers believe it makes up most of the Universe’s mass.

What excites astronomers most about this image is how it shows the clumping of starlight, hot gas and the interaction with dark matter in this galaxy cluster. The blue-green area, including the kicking leg, is a clump of dark matter left behind after the colossal galactic wreck. After most galactic collisions and mergers, galaxies hang together. Dark matter and galaxies clump together. They become larger elliptical galaxies. Scientists expected that here but instead most of the galaxies seem to be zooming away from each other.

Collisions between galaxy clusters, the largest structures in the Universe, offer some clues as to the nature of dark matter. This massive collision is incredibly distant; about 2.4 billion light-years from Earth toward the constellation of Orion, the mythical Hunter.

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