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Colliding clusters turn on radio halos
Posted: 01 September 2010

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A study of 32 galaxy clusters using the Chandra Space Observatory and the Giant Metrewave Radio Telescope (GMRT) shows that collisions between clusters trigger huge radio halos.

Composite image from Chandra (blue, X-ray data) and the Giant Metrewave Radio Telescope (pink, radio data) showing the effect of a collision between two galaxy clusters. Image: X-ray (NASA/CXC/SAO/M.Markevitch); Radio (TIFR/GMRTSAO/INAF/R.Cassano, S.Giacintucci); Optical (DSS).

The new image shows a 12 million light year wide galaxy cluster known as Abell 1758, located 3.2 billion light years away in the constellation Canes Venatici. Clusters are groups of galaxies bound together by gravity, with swathes of hot gas permeating the intracluster medium. They are some of the largest structures in the Universe, with clumps of mysterious dark matter likely contributing to their gravitational strength.

Collisions between clusters generate huge of amounts of energy, and in this image the rich pink and blue hues represent radio and X-ray data respectively. While the X-ray data is indicative of hot gas, the GMRT data reveals radio halos generated by relativistic particles and intense magnetic fields.

The observations of Abell 1758, along with 31 other clusters in the study, show that galaxy clusters with radio halos are still forming, while clusters without clear radio emission are not still accumulating large quantities of material. The result also implies that electrons moving at close to the speed of light are likely accelerated by turbulence stirred up by the merging event.

The rate at which clusters are forming has slowly decreased over the last seven billion years due to the effects of dark energy, a force used to explain the acceleration of the expanding Universe.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!


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