Abell 2218

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Abell 2218
Abell NGC2218 hst big.jpg
Abell 2218. Credit: NASA/ESA
Observation data (Epoch J2000)
Constellation(s) Draco
Right ascension 16h 35m 54s[1]
Declination +66° 13′ 00″[1]
Number of galaxies ~10,000
Richness class 4[2]
Bautz-Morgan classification II [2]
Redshift 0.17560[1]
Distance
(co-moving)
719 Mpc (2,345 Mly) h−1
0.705
[1]
X-ray flux (7.50 ± 9.1%)×10−12 erg s-1 cm-2 (0.1—2.4 keV) [1]
See also: Galaxy groups, Galaxy clusters, List of galaxy clusters

Abell 2218 is a cluster of galaxies about 2 billion light-years away in the constellation Draco.

Acting as a powerful lens, it magnifies and distorts all galaxies lying behind the cluster core into long arcs. The lensed galaxies are all stretched along the cluster's center and some of them are multiply imaged. Those multiple images usually appear as a pair of images with a third — generally fainter — counter image, as is the case for the very distant object. The lensed galaxies are particularly numerous, as we are looking in between two mass clumps, in a saddle region where the magnification is quite large.

Gravitational lensing[edit]

Abell 2218 was used as a gravitational lens to discover the most distant known object in the universe as of 2004. The object, a galaxy some 13 billion years old, is seen from Earth as it would have been just 750 million years after the Big Bang.[3][dubious ]

The color of the lensed galaxies is a function of their distances and types. The orange arc is an elliptical galaxy at moderate redshift (z=0.7). The blue arcs are star-forming galaxies at intermediate redshift (z=1-2.5). The encircled very red pair is the newly discovered star-forming galaxy at about redshift 7.[citation needed]

See also[edit]

References[edit]

  1. ^ a b c d e "NASA/IPAC Extragalactic Database". Results for Abell 2218. Retrieved 2006-09-18. 
  2. ^ a b Abell, George O.; Corwin, Harold G., Jr.; Olowin, Ronald P. (May 1989). "A catalog of rich clusters of galaxies" (PDF). Astrophysical Journal Supplement Series 70 (May 1989): 1–138. Bibcode:1989ApJS...70....1A. doi:10.1086/191333. ISSN 0067-0049. Retrieved March 13, 2012. 
  3. ^ MSNBC: "Galaxy ranks as most distant object in cosmos"

External links[edit]

Coordinates: Sky map 16h 35m 54s, +66° 13′ 00″