Abell 370: Galaxy Cluster Gravitational Lens
Explanation:
What is that strange arc?
While imaging the cluster of galaxies Abell 370, astronomers had noted an unusual
arc to the right of many cluster galaxies.
Although curious, one
initial response was to avoid commenting on the arc because nothing like it
had ever been noted before.
In the mid-1980s, however, better images allowed astronomers to
identify the arc as a prototype of a new kind of
astrophysical phenomenon --
the
gravitational lens
effect of entire
cluster of galaxies
on background galaxies.
Today, we know that this arc actually consists of
two distorted images of a fairly normal galaxy that
happened to lie far behind the huge cluster.
Abell 370's
gravity caused the background galaxies' light -- and others -- to
spread out and come to the observer along
multiple paths, not unlike a distant light appears through the stem of a
wine glass.
In mid-July of 2009, astronomers used the then
just-upgraded Hubble Space Telescope
to image Abell 370 and its gravitational lens images in unprecedented detail.
Almost all of the yellow images
featured here are galaxies in the Abell 370 cluster.
An astute eye can pick up many
strange arcs and
distorted arclets, however,
that are actually images of more distant galaxies.
Studying
Abell 370
and its images gives astronomers a unique window into the distribution of normal
and
dark matter in
galaxy clusters and the universe.
Free Download:
APOD 2017 Calendar: NASA Images
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
