Superclusters Flow Towards a Mysterious Unseen Mass

The reality of superclusters was not apparent until the 1980s, when new telescopes and sensors could produce three-dimensional maps of the Universe. Superclusters are typically seen as long and thin strands of clusters and galaxies, intracluster gases and, presumably, "dark matter" on a two dimensional surface, interspersed by large voids nearly empty of matter.

Astronomers discovered that the galaxies in the Universe are arranged in sheets and walls surrounding large nearly-empty voids. A new study in 2006 has found that spiral galaxies line up like beads on a string, with their spin axes aligned with the filaments that outline voids. The finding supports current galaxy-formation theory, which derives a galaxy's rotation from the uneven distribution of the visible and dark matter from which it coalesces. It predicts a galaxy's axis should be more-or-less perpendicular to the line between the galaxy and the center of the void.

The Virgo Supercluster or Local Supercluster (center of image above) is the irregular supercluster that contains the Virgo Cluster in addition to the Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 110 million light-years. It is one of millions of superclusters in the observable Universe.

It was discovered in the 1980's that not only the Local Group, but all matter out to a distance of at least 50 Mpc is experiencing a flow on the order of 600 km/sec in the direction of the Norma cluster (Abell 3627). Lynden-Bell dubbed the cause of this "The Great Attractor". While astronomers are confident of the velocity of the LS, which has been measured against the Cosmic Microwave Background (CMB), the nature of what is causing it remains one of the great mysteries of astronomy.

Astronomers have known for years that something seems to be pulling our Milky Way and tens of thousands of other galaxies toward itself at a breakneck 22 million kilometers (14 million miles) per hour. But they couldn’t pinpoint exactly what or where it is.

A huge volume of space that includes the Milky Way and super-clusters of galaxies is flowing towards a mysterious, gigantic unseen mass named mass astronomers have dubbed "The Great Attractor," some 250 million light years from our Solar System.

The Milky Way and Andromeda galaxies are the dominant structures in a galaxy cluster called the Local Group which is, in turn, an outlying member of the Virgo supercluster. Andromeda -- about 2.2 million light-years from the Milky Way -- is speeding toward our galaxy at 200,000 miles per hour.

This motion can only be accounted for by gravitational attraction, even though the mass that we can observe is not nearly great enough to exert that kind of pull. The only thing that could explain the movement of Andromeda is the gravitational pull of a lot of unseen mass -- perhaps the equivalent of 10 Milky Way-size galaxies -- lying between the two galaxies.

Meanwhile, our entire Local Group is hurtling toward the center of the Virgo cluster at one million miles per hour.

The Milky Way and its neighboring Andromeda galaxy, along with some 30 smaller ones, form what is known as the Local Group, which lies on the outskirts of a “super cluster” -- a grouping of thousands of galaxies -- known as Virgo (see image below), which is also pulled toward the Great Attractor. Based on the velocities at these scales, the unseen mass inhabiting the voids between the galaxies and clusters of galaxies amounts to perhaps 10 times more than the visible matter.

Even so, adding this invisible material to luminous matter brings the average mass density of the Universe still to within only 10-30 percent of the critical density needed to "close" the Universe. This phenomena suggests that the Universe be "open." Cosmologists continue to debate this question, just as they are also trying to figure out the nature of the missing mass, or "dark matter."

It is believed that this dark matter dictates the structure of the Universe on the grandest of scales. Dark matter gravitationally attracts normal matter, and it is this normal matter that astronomers see forming long thin walls of super-galactic clusters.

Recent measurements with telescopes and space probes of the distribution of mass in M31 -- the largest galaxy in the neighborhood of the Milky Way -- and other galaxies led to the recognition that galaxies are filled with dark matter and have shown that a mysterious force -- a dark energy -- fills the vacuum of empty space, accelerating the Universe's expansion.

Astronomers now recognize that the eventual fate of the Universe is inextricably tied to the presence of dark energy and dark matter. The current standard model for cosmology describes a universe that is 70 percent dark energy, 25 percent dark matter, and only 5 percent normal matter.

We don't know what dark energy is, or why it exists. On the other hand, particle theory tells us that, at the microscopic level, even a perfect vacuum bubbles with quantum particles that are a natural source of dark energy. But a naïve calculation of the dark energy generated from the vacuum yields a value 10120 times larger than the amount we observe. Some unknown physical process is required to eliminate most, but not all, of the vacuum energy, leaving enough left to drive the accelerating expansion of the Universe.

A new theory of particle physics is required to explain this physical process.

The Universe as we see it contains only the stable relics and leftovers of the Big Bang: unstable particles have decayed away with time, and the perfect symmetries have been broken as the Universe has cooled, but the structure of space remembers all the particles and forces we can no longer see around us.

Discovering what it is that makes up the heart of the Great Attractor -- will surely rank as one of the greatest discoveries in the history of science.

Recent findings suggest these motions are the result of gravitational forces from not one, but two things: the Great Attractor, and a conglomerate of galaxies far beyond it.

The location of the Great Attractor was finally determined in 1986 and lies at a distance of 250 million light years from the Milky Way, in the direction of the Hydra and Centaurus constellations. That region of space is dominated by the Norma cluster, a massive cluster of galaxies, and contains a preponderance of large, old galaxies, many of which are colliding with their neighbors, and or radiating large amounts of radio waves.

Major concentration of galaxies lies beyond the Great Attractor, near the so-called Shapley Supercluster, 500 million light-years away -- the most massive known super-cluster. Mapping X-ray luminous galaxy clusters in the Great Attractor region has shown that the pull our galaxy is experiencing is most likely due to both the nearby Great Attractor and these more distant structures.

In the 1987, a group of astronomers known as the "Seven Samurai," at Cal Tech uncovered this coordinated motion of the Milky Way and our several million nearest galactic neighbors. They found that galaxies are very unevenly distributed in space, with galactic super-clusters separated by incredibly huge voids of visible ordinary matter.

The place towards which we all appear headed was originally called the New Supergalactic Center or the Very Massive Object until one of the discoverers, Alan Dressler, decided they needed a more evocative name and came up with "The Great Attractor."

The motion of local galaxies indicated there was something massive out there that are pulling the Milky Way, the Andromeda Galaxy, and other nearby galaxies towards it. For a while, nobody could see what it was, because it lies behind the plane of our Galaxy -- that means the gas and dust in our Galaxy obscures the light from the Great Attractor, and it is outshone by the stars and other objects in our Galaxy.

The Great Attractor is a diffuse concentration of matter some 400 million light-years in size located around 250 million light-years away within the so-called "Centaurus Wall" of galaxies , about seven degrees off the plane of the Milky Way. X-ray observations with the ROSAT satellite then revealed that Abell 3627 is at the center of the Great Attractor. It lies in the so-called Zone of Avoidance, where the dust and stars of the Milky Way's disk obscures as much as a quarter of the Earth's visible sky.

The reality of superclusters did not sink in until the 1980s, when new telescopes and sensors could produce three-dimensional maps of the universe. Superclusters are typically seen as long and thin strands of clusters and galaxies, intracluster gases and, presumably, "dark matter" on a two dimensional surface. The strands are interspersed by large voids nearly empty of matter.




The Daily Galaxy via universe-review.ca, solstation.com, nasa.gov world-science.net

Comments

[Maureen]

What utter nonsense! How can a galaxy,such as the Milky Way,"hurtle towards itself"? This is a poorly written sophomoric attempt to communicate what? It is repetitive and rife with grammatical errors. Needs to be rewritten by someone who knows what they are talkngabo'ut!

We think your comment is what needs rewriting: the article says "pulling" not "hurtle."

The editors. "Astronomers have known for years that something seems to be pulling our Milky Way and tens of thousands of other galaxies toward itself at a breakneck 22 million kilometers (14 million miles) per hour. But they couldn’t pinpoint exactly what or where it is."

[abckontebonkerzyx]

The Shapley Supercluster lies very close to the direction in which the Local Group of galaxies (including our Galaxy) is moving with respect to the CMB frame. This has led many to speculate that the Shapley Supercluster may indeed be one of the major causes of our peculiar motion (the Great Attractor), and has led to a surge of interest in this supercluster.

http://en.wikipedia.org/wiki/Shapley_Supercluster

[James Ph. Kotsybar]

DARK ENERGY QUESTION
-- James Ph. Kotsybar

Could inflation have done more than we know,
shortly after the Big Bang’s first salvo,
and created a dense matter halo
beyond the horizon where we can go?

Beyond the horizon that we can see,
is there a remote possibility
of a most massive field of gravity
that pulls the strings of our reality?

Perhaps it’s just dense matter that’s the source,
accelerating expansion perforce,
and not some new and mysterious force,
or change of gravity’s attractive course,
as though we are bound by a black hole’s skin,
that stretches space to surface dimension.

[orrery]

Stop thinking in terms of gravity. The vacuum of space simply does not exist, but is instead a dense soup of electron & quark plasma that provides a conducting medium for electromagnetic forces over vast cosmic distances. Galactic filaments are organized in large power cable like electromagnetic flows of Birkeland Currents. Gravitational ideas that require 'fictitious dark matter' need not apply to the real world.

[SB]

@ orrery

So why doesn't your soup of matter bits congeal into blobs of high density matter, like planets and stars? Or, what happens to your soup near a planet or black hole? Finally, why can't we see/measure the temperatures of this soup in relationship to the ambient background radiation or see an increase in temp as this soup condenses near massive objects?

[dr burke]

probably

[dr burke]

Gee, do they really think there was ONLY ONE BIG BANG? Probably the other gravitational super cluster is pulling our super clusters along with them, to God knows where? Maybe into some super
cluster meat grinder; a really, really big black hole, that will turn our Newtonian matter into hyper
energy and back we go to become a white hole again and another BIG BANG...

[Asdf]

They are not hurtling. They are revolving around.

Milky Way revolves around Maffei 1. Maffei 1 with many local spiral galaxies revolves around M87. M87 together with the associated supercluster in its gravitational reach revolves around the Great Attractor.

Simple.