Collage of six cluster collisions, with dark-matter maps and x-ray data: This collage shows images of six different galaxy clusters taken with the NASA/ESA Hubble Space Telescope and NASA's Chandra X-ray Observatory. The clusters were observed in a study of how dark matter in clusters of galaxies behaves when the clusters collide. Seventy-two large cluster collisions were studied in total. Using visible-light images from Hubble, the team was able to map the post-collision distribution of stars and also of the dark matter(coloured in blue), which was traced through its gravitational lensing effects on background light. Chandra was used to see the X-ray emission from impacted gas (pink). The team determined that dark matter interacts with itself and everything else even less than previously thought. The clusters shown here are, from left to right and top to bottom: MACS J0416.1-2403, MACS J0152.5-2852, MACS J0717.5+3745, Abell 370, Abell 2744, and ZwCl 1358+62.

Name: Abell 2744, Abell 370, MACS J0152.5-2852, MACS J0416.1-2403, MACS J0717.5+3745, ZwCl 1358+62
Type: Early Universe : Galaxy : Grouping : ClusterEarly Universe : Cosmology : Phenomenon : Dark Matter
Category: Cosmology
Release date: 26 March 2015, 19:00
Credit: NASA/ESA/STScI/CXC, D. Harvey (Ecole Polytechnique Federale de Lausanne, Switzerland; University of Edinburgh, UK), R. Massey (Durham University, UK), T. Kitching (University College London, UK), and A. Taylor and E. Tittley (University of Edinburgh, UK

Hubble spies eight green filaments lit up by past quasar blasts: This image shows the winding green filaments observed by the NASA/ESA Hubble Space Telescope within eight different galaxies. The ethereal wisps in these images were illuminated, perhaps briefly, by a blast of radiation from a quasar — a very luminous and compact region that surrounds a supermassive black hole at the centre of a galaxy. In each of these eight images a quasar beam has caused once-invisible filaments in deep space to glow through a process called photoionisation. Oxygen, helium, nitrogen, sulphur and neon in the filaments absorb light from the quasar and slowly re-emit it over many thousands of years. Their unmistakable emerald hue is caused by ionised oxygen, which glows green. The Hubble team found a total of twenty galaxies that had gas ionised by quasars; those featured here are (from left to right on top row) the Teacup (more formally known as 2MASX J14302986+1339117), NGC 5972, 2MASX J15100402+0740370 and UGC 7342, and (from left to right on bottom row) NGC 5252, Mrk 1498, UGC 11185 and 2MASX J22014163+1151237.

Name: 2MASX J14302986+1339117, 2MASX J15100402+0740370, 2MASX J22014163+1151237, Mrk 1498, NGC 5252, NGC 5972, Teacup Galaxy, UGC 11185, UGC 7342
Type: Local Universe : Nebula : Appearance : EmissionLocal Universe : Galaxy : Activity : AGN : Quasar
Category: NebulaeQuasars and Black Holes
Release date: 2 April 2015, 17:00
Credit: NASA, ESA, Galaxy Zoo Team and W. Keel (University of Alabama, USA)

Hubble view of green filament in Teacup galaxy: This new NASA/ESA Hubble Space Telescope image shows ghostly green filaments, lying within the galaxy Teacup (also known as 2MASX J14302986+1339117). This filament was illuminated by a blast of radiation from a quasar — a very luminous and compact region that surrounds the supermassive black hole at the centre of its host galaxy. Its bright green hue is a result of ionised oxygen, which glows brightly at green wavelengths.

Name: 2MASX J14302986+1339117, Teacup Galaxy
Type: Local Universe : Nebula : Appearance : EmissionLocal Universe : Galaxy : Activity : AGN : Quasar
Category: NebulaeQuasars and Black Holes
Constellation: Bootes
Release date: 2 April 2015, 17:00
Credit: NASA, ESA, W. Keel (University of Alabama, USA)

Hubble view of green filament in galaxy NGC 5972: Twisting in the darkness like a disturbed double helix, NGC 5972 exhibits a remarkable structure of ionised gas, which appears to be reeling in space as a result of a huge disturbance of some kind, possibly a merger with another galaxy. The sweeping trails of gas — both H-alpha and doubly ionised Oxygen, which would both usually be expected in areas of star creation and destruction — reach out into space far beyond the stars that comprise the main body of the galaxy — so far, in fact, that when the Hubble Space Telescope applied the filter necessary to view the gas, it was unable to fit the entire extent of the clouds within its field of view, as seen in this original image. Aside from its intriguing tendrils, NGC 5972 also plays host to an active galactic nucleus. This means a supermassive black hole resides at the centre of the galaxy, and the accretion disc around this monster’s genocidal jaws is rotated with such ferocity that twin beams of plasma are ejected in opposite directions out into the depths of space at close to the speed of light. Because of the vast sums of energy involved, this process can be imaged most effectively in the radio wavelengths, and doing so produces images of structures that are of indescribable magnitudes. Cygnus A provides perhaps the best illustration of this, as seen in this image taken by the NRAO Very Large Array, where the nucleus of the host galaxy appears as nothing more than an insignificant mote of dust, dwarfed by the jets and lobes of highly charged particles protruding outwards with spectacular flamboyance.

Name: NGC 5972
Type: Local Universe : Nebula : Appearance : EmissionLocal Universe : Galaxy : Activity : AGN : Quasar
Category: NebulaeQuasars and Black Holes
Constellation: Serpens Caput
Release date: 2 April 2015, 17:00
Credit: NASA, ESA, W. Keel (University of Alabama, USA)

Hubble view of green filament in galaxy 2MASX J15100402+0740370: This new NASA/ESA Hubble Space Telescope image shows ghostly green filaments, lying within galaxy 2MASX J15100402+0740370. This filament was illuminated by a blast of radiation from a quasar — a very luminous and compact region that surrounds the supermassive black hole at the centre of its host galaxy. Its bright green hue is a result of ionised oxygen, which glows brightly at green wavelengths.

Name: 2MASX J15100402+0740370
Type: Local Universe : Nebula : Appearance : EmissionLocal Universe : Galaxy : Activity : AGN : Quasar
Category: NebulaeQuasars and Black Holes
Constellation: Bootes
Release date: 2 April 2015, 17:00
Credit: NASA, ESA, W. Keel (University of Alabama, USA)