The cluster RDCS1252.9-2927 (detail): Looking back in time to when the universe was in its formative youth, the Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope captured this revealing image of the galaxy cluster RDCS1252.9-2927. This image is made with an additional infrared exposure taken with the European Southern Observatory's Very Large Telescope, shows mature galaxies in a massive cluster that existed when the cosmos was 5 billion years old. The cluster, called RDCS1252.9-2927, is as massive as 200 trillion suns and is the most massive known cluster for its epoch. The image reveals the core of the cluster and is part of a much larger mosaic of the entire cluster. Dominating the core are a pair of large, reddish elliptical galaxies [near centre of image]. Their red colour indicates an older population of stars. Most of the stars are at least 1 billion years old. The two galaxies appear to be interacting and may eventually merge to form a larger galaxy that is comparable to the brightest galaxies seen in present-day clusters. The red galaxies surrounding the central pair are also cluster members. The cluster probably contains many thousands of galaxies, but only about 50 can be seen in this image. The full mosaic reveals several hundred cluster members. Many of the other galaxies in the image, including several of the blue galaxies, are foreground or background galaxies. The colour-composite image was assembled from two observations (through i and z filters) taken between May and June 2002 by the ACS Wide Field Camera, and one image with the ISAAC instrument on the VLT taken in 2002 (combined from a J filter exposure and a K filter exposure).

Name: RDCS1252.9-2927
Type: Early Universe : Galaxy : Grouping : Cluster
Category: CosmologyGalaxies
Constellation: Hydra
Distance: z=1.2 (redshift)
Release date: 31 December 2003, 15:00
Credit: NASA, ESA, J. Blakeslee (Johns Hopkins University), M. Postman ( Space Telescope Science Institute) and P. Rosati, Chris Lidman & Ricardo Demarco (European Southern Observatory)

The cluster TNJ1338-1942 (overview): In this image astronomers are seeing an embryonic cluster as it was when the universe was 1.5 billion years old. The young system, called TNJ1338-1942, is the most distant known developing cluster, or proto-cluster. It is dominated by a massive "baby galaxy" - the green object in the centre. The galaxy is producing powerful radio emissions, and is the brightest galaxy in the proto-cluster. The green colour indicates that the galaxy is emitting glowing hydrogen gas. Its clumpy appearance suggests that it is still in the process of forming. Smaller developing galaxies are scattered around the massive galaxy. The galaxy on the left of the massive galaxy is a foreground galaxy. The bright object in the upper half of the image is a foreground star. This colour-composite image was assembled from observations taken between July 8 and 12, 2002 by the ACS Wide Field Camera.

Name: TNJ1338-1942
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Galaxies
Constellation: Virgo
Distance: z=4.11 (redshift)
Release date: 31 December 2003, 15:00
Credit: NASA, ESA, G. Miley (Leiden Observatory) and R. Overzier (Leiden Observatory)

The cluster RDCS1252.9-2927 (overview): Looking back in time to when the Universe was in its formative youth, the Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope captured this revealing image of the galaxy cluster RDCS1252.9-2927. The image shows the entire cluster (1/15 of a degree, corresponding to about 7 million light-years, across). The cluster probably contains many thousands of galaxies. Most of the other galaxies in the image, including most of the blue galaxies, are foreground or background galaxies. The image, which is made with an additional infrared exposure taken with the European Southern Observatory's Very Large Telescope, shows mature galaxies in a massive cluster that existed when the cosmos was 5 billion years old. The cluster, called RDCS1252.9-2927, is as massive as 200 trillion suns and is the most massive known cluster for its epoch. Dominating the core are a pair of large, reddish elliptical galaxies [near centre of image]. Their red colour indicates an older population of stars. Most of the stars are at least 1 billion years old. The two galaxies appear to be interacting and may eventually merge to form a larger galaxy that is comparable to the brightest galaxies seen in present-day clusters. The red galaxies surrounding the central pair are also cluster members. The colour-composite image was assembled from two observations (through i and z filters) taken between May and June 2002 by the ACS Wide Field Camera, and one image with the ISAAC instrument on the VLT taken in 2002 (combined from a J filter exposure and a K filter exposure).

Name: RDCS1252.9-2927
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Galaxies
Constellation: Hydra
Distance: z=1.2 (redshift)
Release date: 31 December 2003, 15:00
Credit: NASA, ESA, J. Blakeslee (Johns Hopkins University), M. Postman ( Space Telescope Science Institute) and P. Rosati, Chris Lidman & Ricardo Demarco (European Southern Observatory)

Close-up of the Supernova 1993J explosion site (ACS/HRC image): This NASA/ESA Hubble Space Telescope image shows the area in Messier 81 where Supernova 1993J exploded. The companion to the supernova "mother star" that remains after the explosion is seen in the centre of the image. The image is taken with Hubble's Advanced Camera for Surveys and is a combination of four exposures taken with ACS' High Resolution Camera. The exposures were taken through two near-UV filters (250W, 2100 seconds and 330W, 1200 seconds) shown in purple and blue, a deep blue filter (435W, 1000 seconds) shown in green and a green filter (555W, 1120 seconds) shown in red. The quarter-circle around the supernova companion is a so-called light echo originating from sheets of dust in the galaxy reflecting light from the original supernova explosion. The timing of the appearance of these echoes can be used to map out the dust structure around the supernova. The light echo was detected in late 2002 and early 2003 by two competing groups of scientists.

Name: Messier 81, NGC 3031, SN 1993J
Type: Local Universe : Star : Evolutionary Stage : SupernovaLocal Universe : Galaxy : Component : Spiral Arm
Category: GalaxiesStars
Constellation: Ursa Major
Distance: 12 million light years
Release date: 7 January 2004, 15:00
Credit: ESA and Justyn R. Maund (University of Cambridge)

Messier 81 spiral arm (WFPC2 image) ˜: This NASA/ESA Hubble Space Telescope image shows a small portion of one of Messier 81's spiral arms. It extends about 0.03 x 0.03 degrees. The supernova companion is the bluish star in the upper right hand corner. Dust lanes in the spiral arms of the galaxy are seen, as well as many other stars and a few star forming nebulae. The image is composed of four separate exposures from the ESO/ST-ECF Archive through a blue filter, a green filter, a red filter and a near-infrared filter. The image was taken with Hubble's Wide Field and Planetary Camera 2.

Name: Messier 81, NGC 3031
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Ursa Major
Distance: 12 million light years
Release date: 7 January 2004, 15:00
Credit: ESA and Justyn R. Maund (University of Cambridge)Acknowledgement: Bob Kirshner (Harvard University, USA)

Grand Spiral Messier 81 (ground-based): This ground-based image shows the spiral galaxy Messier 81 in its entirety. The image is a combination of exposures from the Isaac Newton Telescope on La Palma (courtesy of Jonathan Irwin) and Digitized Sky Survey 2 images.

Name: Messier 81, NGC 3031
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Ursa Major
Distance: 12 million light years
Release date: 7 January 2004, 15:00
Credit: ESA/INT/DSS2