Shedding Light on the Cosmic Skeleton

Nov 03, 2009
Astronomers have tracked down a gigantic, previously unknown assembly of galaxies located almost seven billion light-years away from us. The discovery, made possible by combining two of the most powerful ground-based telescopes in the world -- ESO's Very Large Telescope and NAOJ’s Subaru Telescope -- is the first observation of such a prominent galaxy structure in the distant Universe, providing further insight into the cosmic web and how it formed. This 3-D illustration shows the position of the galaxies and reveals the extent of this gigantic structure. The galaxies located in the newly discovered structure are shown in red. Galaxies that are either in front or behind the structure are shown in blue. Credit: ESO/L. Calçada/Subaru/National Astronomical Observatory of Japan/M. Tanaka

(PhysOrg.com) -- Astronomers have tracked down a gigantic, previously unknown assembly of galaxies located almost seven billion light-years away from us. The discovery, made possible by combining two of the most powerful ground-based telescopes in the world, is the first observation of such a prominent galaxy structure in the distant Universe, providing further insight into the cosmic web and how it formed.

"Matter is not distributed uniformly in the Universe," says Masayuki Tanaka from ESO, who led the new study. "In our cosmic vicinity, stars form in galaxies and galaxies usually form groups and clusters of galaxies. The most widely accepted cosmological theories predict that matter also clumps on a larger scale in the so-called 'cosmic web', in which galaxies, embedded in filaments stretching between voids, create a gigantic wispy structure."

These filaments are millions of light years long and constitute the skeleton of the Universe: galaxies gather around them, and immense galaxy clusters form at their intersections, lurking like giant spiders waiting for more matter to digest. Scientists are struggling to determine how they swirl into existence. Although massive filamentary structures have been often observed at relatively small distances from us, solid proof of their existence in the more distant Universe has been lacking until now.

The team led by Tanaka discovered a large structure around a distant cluster of galaxies in images they obtained earlier. They have now used two major ground-based telescopes to study this structure in greater detail, measuring the distances from Earth of over 150 galaxies, and, hence, obtaining a three-dimensional view of the structure. The spectroscopic observations were performed using the VIMOS instrument on ESO's Very Large and FOCAS on the Subaru Telescope, operated by the National Astronomical Observatory of Japan.

This image, obtained with the Subaru Telescope, operated by the National Astronomical Observatory of Japan was used by a team of astronomers, led by Masayuki Tanaka from the European Southern Observatory (ESO), to uncover a gigantic, previously unknown assembly of galaxies located almost seven billion light-years away from us. This structure was confirmed by further observations made using ESO’s Very Large Telescope and Subaru. It is the first observation of such a prominent galaxy structure in the distant Universe, providing further insight into the cosmic web and how it formed. The galaxies located in the newly discovered structure are shown in red. Galaxies that are either in front or behind the structure are shown in blue. Credit: ESO/Subaru/National Astronomical Observatory of Japan/M. Tanaka

Thanks to these and other observations, the astronomers were able to make a real demographic study of this structure, and have identified several groups of galaxies surrounding the main . They could distinguish tens of such clumps, each typically ten times as massive as our own Milky Way galaxy —and some as much as a thousand times more massive — while they estimate that the mass of the cluster amounts to at least ten thousand times the mass of the Milky Way. Some of the clumps are feeling the fatal gravitational pull of the cluster, and will eventually fall into it.

"This is the first time that we have observed such a rich and prominent structure in the distant Universe," says Tanaka. "We can now move from demography to sociology and study how the properties of galaxies depend on their environment, at a time when the was only two thirds of its present age."

The filament is located about 6.7 billion light-years away from us and extends over at least 60 million light-years. The newly uncovered structure does probably extend further, beyond the field probed by the team, and hence future observations have already been planned to obtain a definite measure of its size.

More information:
• This research was presented in a paper published as a letter in the Astronomy & Astrophysics Journal: 'The spectroscopically confirmed huge cosmic structure at z = 0.55', by Tanaka et al. www.aanda.org/10.1051/0004-6361/200912929
• A first glimpse of the very early universal web, obtained with much less than here, is presented in ESO 11/01.

Source: ESO (news : web)

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User comments : 7

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frajo
2 / 5 (2) Nov 03, 2009
and immense galaxy clusters form at their intersections, lurking like giant spiders waiting for more matter to digest. Scientists are struggling to determine how they swirl into existence.

In the ekpyrotic model the "creation" of all sizes of galaxy clusters happens quite naturally by the collision ( big crunch => big bang) of two branes.
GSwift7
5 / 5 (1) Nov 03, 2009
It would seem that the froth of the early universe got bubbles in it as it cooled then? The structure they describe seems very much like the intersection of bubbles stacked on top of each other.
yyz
5 / 5 (1) Nov 03, 2009
GSwift7, you seem to have grasped what researchers have actually found in their deep extragalactic surveys. Galaxies do appear to form on the 'surface' of large, bubble-like structures and gather into filaments and clusters at the confluence of two (or more) bubbles. A few galaxies show up in isolated 'void' regions within the bubble-like structures. But most galaxies reside on the 'surface' and confluences of these bubbles. Supercomputer simulations of cosmic structure also show similar 'bubbles', 'voids', and 'filaments'.
brant
not rated yet Nov 03, 2009
"Scientists are struggling to determine how they swirl into existence. Although massive filamentary structures have been often observed at relatively small distances from us, solid proof of their existence in the more distant Universe has been lacking until now."

The Bennett Pinch law also allows for the formation of filaments as well as accounts for plasma interactions. It would easily explain the structure of the universe from known experimental principles.
It would actually be better than gravity because it also explains magnetic fields and their preferential alignment within filament structures.
NotAsleep
not rated yet Nov 04, 2009
How much more matter do we have to find before die-hard dark matter fans start to question that theory...
vidar_lund
not rated yet Nov 05, 2009
How much more matter do we have to find before die-hard dark matter fans start to question that theory...


Matter found 7 billion light years away does not explain why the Milky-way and other galaxies in our neighborhood are spinning much faster than what they are supposed to based on the amount of stars and gas in those galaxies.
NotAsleep
not rated yet Nov 05, 2009
But if we didn't notice enormous structures at that distance, isn't it reasonable to believe that we missed smaller ones in our own galaxy? There's so much matter in our galaxy alone, I find it hard to believe that we have a perfect understanding of exactly how much there is.

I'm certainly not trying to disprove dark matter/energy, just hoping for more open mindedness on the limitations of what we "know"

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