Galaxy cluster Abell 520's hot gas (Chandra): This image shows regions of hot gas at the core of merging galaxy cluster Abell 520, detected by NASA's Chandra X-ray Observatory. The gas is evidence that a collision between massive galaxy clusters took place.

Name: Abell 520
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Cosmology
Constellation: Orion
Distance: 2 billion light years
Release date: 23 March 2012, 17:01
Credit: NASA, ESA, CXO, and M.J. Jee (University of California, Davis)

Galaxy cluster Abell 520's mass (HST WFPC2): This image shows the location of most of the mass in merging galaxy cluster Abell 520's core, 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 Hubble Wide Field Planetary Camera 2 observations, by detecting how light from distant objects is distorted by the cluster galaxies, an effect called gravitational lensing. 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, 17:06
Credit: NASA, ESA, and M.J. Jee (University of California, Davis)

Eta Carinae light echo region — 10 March 2003: The double-star system Eta Carinae, about 120 times more massive than the Sun, produced a spectacular outburst that was seen on Earth from 1837 to 1858. This image shows an area near Eta Carinae that is not illuminated by the double-star system's outburst. The image was taken in March 2003 with the NOAO Optical Astronomy Observatory's Blanco 4-metre telescope at Cerro Tololo Inter-American Observatory in Chile.

Name: Eta Carinae
Type: Milky Way : Star : Type : Variable
Category: Stars
Constellation: Carina
Release date: 20 February 2012, 12:12
Credit: NOAO, AURA, NSF, and N. Smith (University of Arizona)

Eta Carinae light echo brightening — 10 May 2010: The double-star system Eta Carinae, about 120 times more massive than the Sun, produced a spectacular outburst that was seen on Earth from 1837 to 1858. This image shows the light from Eta Carinae's outburst illuminating the dust clouds near the doomed star system as it moves through them. The effect is like shining a flashlight on different regions of a vast cavern. The image was taken in March 2010 with the NOAO Optical Astronomy Observatory's Blanco 4-metre telescope at the Cerro Tololo Inter-American Observatory in Chile.

Name: Eta Carinae
Type: Milky Way : Star : Type : Variable
Category: Stars
Constellation: Carina
Release date: 20 February 2012, 12:14
Credit: NASA, NOAO, and A. Rest (STScI)

Eta Carinae light echo brightening — 6 February 2011: The double-star system Eta Carinae, about 120 times more massive than the Sun, produced a spectacular outburst that was seen on Earth from 1837 to 1858. This image shows the light from Eta Carinae's outburst illuminating the dust clouds near the doomed star system as it moves through them. The effect is like shining a flashlight on different regions of a vast cavern. The image was taken in February 2011 with the NOAO Optical Astronomy Observatory's Blanco 4-metre telescope at the Cerro Tololo Inter-American Observatory in Chile.

Name: Eta Carinae
Type: Milky Way : Star : Type : Variable
Category: Stars
Constellation: Carina
Release date: 20 February 2012, 12:16
Credit: NASA, NOAO, and A. Rest (STScI)