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The NASA / ESA Hubble
Space Telescope

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has captured a new image
of the galaxy NGC 1132

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which is most likely to
be a 'cosmic fossil'

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the aftermath of an enormous
multi-galactic pile-up

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where the carnage of
collision after collision

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has built up a brilliant but
fuzzy giant elliptical galaxy

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far outshining typical galaxies.

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This is the Hubblecast.

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News and images from the
NASA / ESA Hubble Space Telescope.

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Travelling through time and space
with our host, Dr. J

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EPISODE 13: Gargantuan galaxy NGC 1132.
A "cosmic fossil".
a.k.a. Dr. Joe Liske.

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Welcome to the Hubblecast.

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In this episode
we'll take a closer look

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at the latest image from
the Hubble Space Telescope.

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It shows the giant elliptical
galaxy NGC 1132.

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Now you may ask:

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what's so special about this fuzzy,
seemingly bland object?

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Well, the interesting thing about it
is not so much what it looks like today

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but rather what
happened in its past.

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So lets try to trace its history
by taking a very close look

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at its present day features.

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NGC 1132 is located about 320 million
light years away from Earth.

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in the constellation of Eridanus,
the River.

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At first glance NGC 1132 looks like
any other ordinary elliptical galaxy:

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it is smooth, featureless and contains
hundreds of millions of stars

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whose yellowish colour is a
tell-tale sign of their great age.

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But closer up we see that
NGC 1132 is rather special.

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It's humongous!

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Many times larger than
the average elliptical galaxy.

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It belongs to a category of
galaxies called giant ellipticals.

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Seen in visible light NGC 1132
appears as a single,

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almost isolated, giant galaxy.

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But this is only the
tip of the iceberg.

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Scientists have found
that NGC 1132

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resides in an enormous
halo of dark matter,

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comparable to the amount
usually found in an entire group

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of tens to hundreds of galaxies.

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It also has a strong X-ray glow
from an abundance of hot gas,

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an amount normally only
found in galaxy groups.

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In fact its X-ray glow extends
over a region of space

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ten times larger than the
120,000 light-years radius

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seen in visible light.

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This is a glow equal in size to that
of an entire group of galaxies.

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So there is enough dark matter
and hot gas here

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for an entire group of galaxies

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and yet we see only a single
although gargantuan galaxy.

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Well, actually not quite.

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If we look closely at the image
we can see that NGC 1132

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is actually associated with a whole
bunch of small dwarf galaxies,

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which look a little bit
like huge wads of cotton,

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but there are definitely
no medium-sized galaxies.

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So what's going on?

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Well, the most likely explanation
is that NGC 1132

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is the result of
galactic cannibalism.

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It's probably
a so called 'fossil group'.

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In other words
what we are looking at here

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are the remains of
an entire group of galaxies

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that have all merged
together into a single galaxy

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at some point in its past.

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Now if we examine
the image closely

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we can also see that NGC 1132

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is surrounded by thousands
of ancient globular clusters,

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swarming around the galaxy
like bees around the hive.

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These globular clusters
are most likely survivors

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of the disruption
of their parent galaxies

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that have been swallowed
by NGC 1132.

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Because of that
they can tell us a lot

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about the merging history
of the whole group.

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There is also a stunning tapestry
of background galaxies

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that are much further away
and have nothing to do

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with the fossil group
in the foreground.

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The formation of "fossil groups"
remains a puzzle

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that astronomers are
still trying to solve.

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The most likely explanation is
that they are the end product

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of a cosmic feeding frenzy
in which a large galaxy

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devours all its neighbours.

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An alternative
but less favoured view

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is that they may be
very rare objects

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that formed in a region
of space or period of time

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where the growth
of medium-sized galaxies

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was somehow suppressed,

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and only one
large galaxy formed.

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Many galaxies,
including our own Milky Way,

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reside in groups that are
gravitationally bound together.

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There is plenty of evidence that
the Milky Way is also a cannibal

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and has snacked on
a number of smaller galaxies

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throughout its lifetime, inheriting
the stars in the process.

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So what will happen to the
Milky Way and its neighbours

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over the next
few billions of years.

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Well, that is precisely
one of the questions

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that astronomers are
trying to answer

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when they study the structure
and evolution of other galaxies

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such as NGC 1132.

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By analysing their properties it is
possible to trace back their history

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and to better understand
what will happen

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in our own neighbourhood
in the future.

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This is Dr. J
signing off for the Hubblecast.

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Once again, nature has surprised us
beyond our wildest imagination...

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Hubblecast is produced
by ESA / Hubble

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at the European
Southern Observatory in Germany.

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The Hubble mission is a project
of international cooperation

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between NASA and
the European Space Agency.