Abell 2218

Galaxy cluster
name = Abell 2218


caption = Abell 2218. Credit: NASA/ESA
epoch=J2000
ra=RA|16|35|54cite web
title=NASA/IPAC Extragalactic Database
work=Results for Abell 2218
url=http://nedwww.ipac.caltech.edu/
accessdate=2006-09-18]
dec=DEC|+66|13|00
constellation = Draco
member_no = ~10,000
Redshift=0.18
brightest_member =
other_names =

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.

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.

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.

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.

ee also

* Abell 370
* Abell 1835 IR1916
* IOK-1

External links

* [http://www.spacetelescope.org/news/html/heic0113.html Release about Abell 2218 at ESA/Hubble]

References