MACS 1206 a Galaxy Cluster Gravitational Len

Father Sky — Tue, 18 Oct 2011 10:19:29 +0000

It is difficult to hide a galaxy behind a cluster of galaxies.

The closer cluster's gravity will act like a
huge lens, pulling images of the distant galaxy around the sides and greatly distorting them.

This is just the case observed in the above recently released image from the CLASH survey with the
Hubble Space Telescope.

The cluster
MACS J1206.2-0847 is composed of many galaxies and is lensing the image of a yellow-red background galaxy into the
huge arc on the right.

Careful inspection of the image will reveal at least several other lensed background galaxies -- many appearing as elongated wisps.

The foreground
cluster can only create such smooth arcs if most of its mass is smoothly distributed
dark matter -- and therefore not concentrated in the cluster galaxies visible.

Analyzing the positions of these
gravitational arcs also gives astronomers a method to estimate the
dark matter distribution in galaxy clusters, and infer from that when these
huge conglomerations of galaxies
began to form.

Read the full story:
MACS 1206: A Galaxy Cluster Gravitational Len

Tags: Galaxy groups and clusters, gravitational arcs, galaxy cluster, red background, Gravitational lens, cluster galaxies, yellow-red background galaxy

The Einstein Cross Gravitational Lens

Father Sky — Mon, 28 Feb 2011 15:34:23 +0000

Most galaxies have a single nucleus -- does this galaxy have four?

The strange answer leads
astronomers
to conclude that the nucleus of the surrounding galaxy is not even visible in
this image.

The central
cloverleaf is rather light emitted from a background

quasar.

The gravitational field of the visible foreground
galaxy
breaks light
from this distant
quasar
into four distinct images.

The quasar must be
properly aligned behind the center of a massive galaxy for a
mirage like this to be evident.

The general effect is known as
gravitational lensing, and this specific case is known as the
Einstein Cross.

Stranger still, the images of the
Einstein Cross vary in relative brightness,
enhanced occasionally by the additional
gravitational microlensing
effect of specific stars in the foreground galaxy.

Tags: galaxy, lens, einstein cross, Cross, foreground galaxy, Einstein

Skylook | Astronomy | Eclipses | Telescopes » Gravitational

MACS 1206 a Galaxy Cluster Gravitational Len

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The Einstein Cross Gravitational Lens

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