A cluster and a sea of galaxies (w/ Video)

May 05, 2010
This wide-field, deep image reveals thousands of galaxies crowding an area on the sky roughly as large as the full moon. These galaxies span a vast range of distances from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos, especially in the upper part of the image. The more distant, instead, appear just like faint blobs -- their light has traveled through the universe for eight billion years or more before reaching Earth. Beginning in the center of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a massive galaxy cluster, designated Abell 315, about two billion light-years away from us. To complement the enormous range of cosmic distances and sizes surveyed by this image, a handful of objects much smaller than galaxies and galaxy clusters and much closer to Earth are dotted throughout the field: besides several stars, many asteroids are also visible as blue, green or red trails. This image has been taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile. It is a composite of several exposures acquired using three different broadband filters, for a total of almost one hour in the B filter and about one and a half hour in the V and R filters. The field of view is 34 x 33 arcminutes. Credit: ESO/J. Dietrich

(PhysOrg.com) -- A new wide-field image released today by ESO displays many thousands of distant galaxies, and more particularly a large group belonging to the massive galaxy cluster known as Abell 315. As crowded as it may appear, this assembly of galaxies is only the proverbial "tip of the iceberg", as Abell 315 -- like most galaxy clusters -- is dominated by dark matter. The huge mass of this cluster deflects light from background galaxies, distorting their observed shapes slightly.

When looking at the sky with the unaided eye, we mostly only see stars within our and some of its closest neighbours. More distant galaxies are just too faint to be perceived by the human eye, but if we could see them, they would literally cover the sky. This new image released by ESO is both a wide-field and long-exposure one, and reveals thousands of galaxies crowding an area on the sky roughly as large as the full Moon.

These galaxies span a vast range of distances from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos, especially in the upper part of the image. The more distant appear just like the faintest of blobs — their light has travelled through the Universe for eight billion years or more before reaching Earth.

This video is not supported by your browser at this time.
This video zooms on the cluster of galaxies Abell 315, located in between the faint, red and blue galaxies and the Earth, about two billion light-years away from us. It lies in the constellation of Cetus. Credit: ESO/ Digitized Sky Survey 2

Beginning in the centre of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a cluster, designated with the number 315 in the catalogue compiled by the American astronomer George Abell in 1958. The cluster is located between the faint, red and blue galaxies and the Earth, about two billion light-years away from us. It lies in the constellation of Cetus (the Whale).

Galaxy clusters are some of the largest structures in the Universe held together by gravity. But there is more in these structures than the many galaxies we can see. Galaxies in these giants contribute to only ten percent of the mass, with hot gas in between galaxies accounting for another ten percent. The remaining 80 percent is made of an invisible and unknown ingredient called dark matter that lies in between the galaxies.

The presence of is revealed through its gravitational effect: the enormous mass of a acts on the light from galaxies behind the cluster like a cosmic magnifying glass, bending the trajectory of the light and thus making the galaxies appear slightly distorted. By observing and analysing the twisted shapes of these background galaxies, astronomers can infer the total mass of the cluster responsible for the distortion, even when this mass is mostly invisible. However, this effect is usually tiny, and it is necessary to measure it over a huge number of galaxies to obtain significant results: in the case of Abell 315, the shapes of almost 10 000 faint galaxies in this image were studied in order to estimate the total mass of the cluster, which amounts to over a hundred thousand billion times the mass of our Sun.

To complement the enormous range of cosmic distances and sizes surveyed by this image, a handful of objects much smaller than galaxies and galaxy clusters and much closer to Earth are scattered throughout the field: besides several stars belonging to our galaxy, many asteroids are also visible as blue, green or red trails. These objects belong to the main asteroid belt, located between the orbits of Mars and Jupiter, and their dimensions vary from some tens of kilometres, for the brightest ones, to just a few kilometres in the case of the faintest ones.

This image has been taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile. It is a composite of several exposures acquired using three different broadband filters, for a total of almost one hour in the B filter and about one and a half hours in the V and R filters. The field of view is 34 x 33 arcminutes.

Explore further: A spectacular landscape of star formation

More information: A weak lensing study of the galaxy cluster Abell 315 has been published in a paper that appeared in Astronomy & Astrophysics in 2009 (“Weak lensing observations of potentially X-ray underluminous galaxy clusters”, by J. Dietrich et al.). adsabs.harvard.edu/abs/2009A%26A...499..669D

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El_Nose
not rated yet May 05, 2010
which amounts to over a hundred thousand billion times the mass of our Sun.


hundred thousand billion --- OR -- one hundred trillion

which one is eaiser to understand???
Au-Pu
1 / 5 (1) May 05, 2010
The margin for error in such attempts to prove dark matter is so great as to render any results as seriously doubtful.
With such a discrepancy in the volume of matter might it not be a more worthwhile exercise to question the big bang theory?
Or has the big bang theory assumed the status of a cosmological religion?
jsa09
not rated yet May 06, 2010
@ el_nose
which amounts to over a hundred thousand billion times the mass of our Sun.
is much easier to understand.

trillions mean different things in different versions of English.
Titto
not rated yet May 06, 2010
Just imagine where one would be if one is between galaxies????I cannot understand my brain will explode!! This creation is endless. Where is it? What space is it in?The reason for evrything else but earth?
frajo
not rated yet May 06, 2010
which amounts to over a hundred thousand billion times the mass of our Sun.
is much easier to understand.
Depends on what you are accustomed to.
trillions mean different things in different versions of English.
In the US, billion=10**9 and trillion=10**12.
In Europe, billion=10**12 and trillion=10**18.
Whether the English are Europeans, I don't know.
Fortunately, all of us use the same prefixes - giga, tera, peta, exa.
frajo
not rated yet May 06, 2010
The margin for error in such attempts to prove dark matter is so great as to render any results as seriously doubtful.
They don't attempt to prove DM. Instead, they try to interprete observational data in the light of the dominant standard cosmological model.
With such a discrepancy in the volume of matter might it not be a more worthwhile exercise to question the big bang theory?
There are a couple of alternative models, some of them quite promising. Unfortunately, none of them is testable yet.
Or has the big bang theory assumed the status of a cosmological religion?
No. Nevertheless, it's a bit of mind stretching to assume to know the undistorted shapes of 10000 background galaxies (of which only their distorted images can be seen) in order to calculate the cluster mass of Abell 315. The contents of the visible universe might not be distributed uniformly enough to validate such an (obviously statistical) approach.
Shootist
1 / 5 (1) May 06, 2010
which amounts to over a hundred thousand billion times the mass of our Sun.
is much easier to understand.
Depends on what you are accustomed to.
trillions mean different things in different versions of English.
In the US, billion=10**9 and trillion=10**12.
In Europe, billion=10**12 and trillion=10**18.
Whether the English are Europeans, I don't know.
Fortunately, all of us use the same prefixes - giga, tera, peta, exa.


so what does 10^9 equal in the country formerly known as England?
LuckyBrandon
1 / 5 (1) May 06, 2010
nobody will believe dark matter is real until a dark matter organism holds up a sign post pointed at our telescopes that says "we are here, and we live on what you piddly humans call dark matter"...thats my take anyways...i still say the same, watch it be real, and watch it be solid just like our normal visible matter...itll be a bitch when we get to the end of our solar system and literally hit a wall...that would shut up neigh-sayers though I'd think (or hope)...

To me, the image did not look all that impressive..albeit, I only saw the blown up image from here, which could make it crappier resolution I'm sure...but still, it doesn't look any different than any other pic we've taken of the distant universe....
Alizee
May 09, 2010
This comment has been removed by a moderator.
LuckyBrandon
not rated yet May 10, 2010
alizee-my point with my post is that is does not matter if dark matter is detected...nobody (as in the normal person out there in the world) will believe it until ET stands up in there and waves...
In no way whatseover was I saying that any type of creature had to exist. The arguments will persist even after definitive proof, just as they have regarding the big bang theory...