Centre of M31: This Hubble Space Telescope image centres on the 100-million-solar-mass black hole at the hub of the neighboring spiral galaxy M31, or the Andromeda galaxy, one of the few galaxies outside the Milky Way visible to the naked eye and the only other giant galaxy in the Local Group. This is the sharpest visible-light image ever made of the nucleus of an external galaxy.

Name: Andromeda Galaxy, M 31, Messier 31, NGC 224
Type: Local Universe : Galaxy : Component : Center/Core
Category: Galaxies
Constellation: Andromeda
Release date: 11 January 2012, 20:21
Credit: NASA, ESA, and T. Lauer (National Optical Astronomy Observatory)

Ground-based image of Andromeda Galaxy, M31: This image of the Andromeda galaxy was taken on 13 January 2001, with the WIYN/KPNO 0.9-metre Mosaic I by T. Rector and B. Wolpa of the National Optical Astronomy Observatory in Tucson, Arizona (USA).

Name: Andromeda Galaxy, M 31, Messier 31, NGC 224
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Release date: 11 January 2012, 18:52
Credit: T. Rector and B. Wolpa (NOAO/AURA/NSF)

Hubble sees giant lensed galaxy arc: Thanks to the presence of a natural "zoom lens" in space, this is a close-up look at the brightest distant "magnified" galaxy in the Universe known to date. It is one of the most striking examples of gravitational lensing, where the gravitational field of a foreground galaxy bends and amplifies the light of a more distant background galaxy. In this image the light from a distant galaxy, nearly 10 billion light-years away, has been warped into a nearly 90-degree arc of light in the galaxy cluster RCS2 032727-132623. The galaxy cluster lies 5 billion light-years away. The background galaxy's image is over three times brighter than typically lensed galaxies. The natural-colour image was taken in March 2011 with the Hubble Space Telescope's Wide Field Camera 3.

Name: RCS2 032727-132623, RCSGA 032727-132609
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Cosmology
Constellation: Eridanus
Release date: 8 February 2012, 13:46
Credit: NASA, ESA, J. Rigby (NASA Goddard Space Flight Center), K. Sharon (Kavli Institute for Cosmological Physics, University of Chicago), and M. Gladders and E. Wuyts (University of Chicago)

Galaxy cluster RCS2 032727-132623 (uncropped): Galaxy cluster RCS2 032727-132623 (uncropped).

Name: RCS2 032727-132623, RCSGA 032727-132609
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Cosmology
Constellation: Eridanus
Release date: 8 February 2012, 13:50
Credit: NASA, ESA, J. Rigby (NASA Goddard Space Flight Center), K. Sharon (Kavli Institute for Cosmological Physics, University of Chicago), M. Gladders and E. Wuyts (University of Chicago), and the Hubble Heritage Team (STScI/AURA)

Merging galaxy cluster Abell 520: This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters. The natural-colour image of the galaxies was taken with the NASA/ESA Hubble Space Telescope and with the Canada-France-Hawaii Telescope in Hawaii. Superimposed on the image are "false-coloured" maps showing the concentration of starlight, hot gas, and dark matter in the cluster. Starlight from galaxies, derived from observations by the Canada-France-Hawaii Telescope, is coloured orange. The green-tinted regions show hot gas, as detected by NASA's Chandra X-ray Observatory. The gas is evidence that a collision took place. The blue-coloured areas pinpoint the location of most of the mass in the cluster, which is dominated by dark matter. Dark matter is an invisible substance that makes up most of the Universe's mass. The dark-matter map was derived from the Hubble Wide Field Planetary Camera 2 observations by detecting how light from distant objects is distorted by the cluster of galaxies, an effect called gravitational lensing. The blend of blue and green in the centre of the image reveals that a clump of dark matter resides near most of the hot gas, where very few galaxies are found. This finding confirms previous observations of a dark-matter core in the cluster. The result could present a challenge to basic theories of dark matter, which predict that galaxies should be anchored to dark matter, even during the shock of a collision. Abell 520 resides 2.4 billion light-years away.

Name: Abell 520
Type: Early Universe : Galaxy : Grouping : ClusterEarly Universe : Cosmology : Phenomenon : Dark Matter
Category: Cosmology
Constellation: Orion
Distance: 2 billion light years
Release date: 23 March 2012, 15:59
Credit: NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)

Galaxy custer Abell 520 (HST-CFHT-CXO composite): This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters. The natural-colour image of the galaxies was taken with the NASA/ESA Hubble Space Telescope and with the Canada-France-Hawaii Telescope in Hawaii. Superimposed on the image are maps showing the concentration of starlight, hot gas, and dark matter. Starlight from galaxies, derived from observations by the Canada-France-Hawaii Telescope, is coloured orange. The green-tinted regions show hot gas, as detected by NASA's Chandra X-ray Observatory. The gas is evidence that a collision took place. The blue-coloured areas pinpoint the location of most of the mass in the cluster, which is dominated by dark matter. Dark matter is an invisible substance that makes up most of the Universe's mass. The dark-matter map was derived from the Hubble Wide Field Planetary Camera 2 observations by detecting how light from distant objects is distorted by the cluster of galaxies, an effect called gravitational lensing. The blend of blue and green in the centre of the image reveals that a clump of dark matter resides near most of the hot gas, where very few galaxies are found. This finding confirms previous observations of a dark-matter core in the cluster. The result could present a challenge to basic theories of dark matter, which predict that galaxies should be anchored to dark matter, even during the shock of a collision. Abell 520 resides 2.4 billion light-years away.

Name: Abell 520
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Cosmology
Constellation: Orion
Distance: 2 billion light years
Release date: 23 March 2012, 16:27
Credit: NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)

Galaxy cluster Abell 520 (CFHT and HST): The natural-colour image of the galaxies was taken with the NASA/ESA Hubble Space Telescope and the Canada-France-Hawaii Telescope in Hawaii. Abell 520 formed from a violent collision of massive galaxy clusters and resides 2.4 billion light-years away.

Name: Abell 520
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Cosmology
Constellation: Orion
Distance: 2 billion light years
Release date: 23 March 2012, 16:31
Credit: NASA, ESA, CFHT, and M.J. Jee (University of California, Davis)

Galaxy cluster Abell 520's luminosity (CFHT): This image shows the concentration of starlight at the core of merging galaxy cluster Abell 520. The map was derived from observations by the Canada-France-Hawaii Telescope in Hawaii. Abell 520 resides 2.4 billion light-years away.

Name: Abell 520
Type: Early Universe : Star : Grouping : Cluster
Category: Cosmology
Constellation: Orion
Distance: 2 billion light years
Release date: 23 March 2012, 16:48
Credit: NASA, ESA, CFHT, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)