Distortion from a Distant Cluster
Explanation:
This stunning
color deep sky view toward the constellation Pisces was
made with data from a fast, sensitive, digital detector known as the
Big
Throughput Camera operating at
Cerro Tololo
Inter-American
Observatory in Chile.
Hardly noticeable in the original picture is the small
cluster of about 15 galaxies nearly 3
billion light-years
distant,
circled at the lower right.
In fact, this distant cluster was not discovered by noticing
its appearance in the image at all, but instead by mapping
the subtle distortions created by its gravity.
As predicted by
Einstein's General Relativity theory,
the cluster's gravitational mass acts like a lens, bending light
and distorting the shape of background galaxies.
The effect is known as
gravitational lensing.
Computer
mapping of
weak distortions of background galaxy shapes
across the Big Throughput image revealed that the large scale
distribution of mass in that part of the sky was concentrated in a
small region.
That region turned out to correspond to the galaxy
cluster -- the first time such an object
has
been discovered
on the basis of its mass properties rather than its light.
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.
