Abell 2218

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Abell 2218
Abell NGC2218 hst big.jpg
Abell 2218. Credit: NASA/ESA
Observation data (Epoch J2000)
Right ascension 16h 35m 54s[1]
Declination+66° 13′ 00″[1]
Number of galaxies~10,000
Richness class4[2]
Bautz–Morgan classificationII [2]
719 Mpc (2,345 Mly) h−1
X-ray flux(7.50 ± 9.1%)×1012 erg s−1 cm−2 (0.1–2.4 keV) [1]
See also: Galaxy group, Galaxy cluster, List of galaxy groups and 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]

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). There is a pair of images in the lower part of the picture of the newly discovered star-forming galaxy[4] at about redshift 7.[citation needed]

See also[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. ^ NBC News: "Galaxy ranks as most distant object in cosmos"
  4. ^ information@eso.org. "Hubble and Keck's newly discovered galaxy 'building block'". www.spacetelescope.org. Retrieved 2017-08-23.

External links[edit]

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