Dork Matter

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Dork Matter - because nature's wrong but scientists can not be

Dark stuff is amazing. We can not directly see it, measure it, or even prove its existence but not only is all Dark stuff a fact it is everywhere and nearly everything. Dark Matter is 95% of the Universe. Imagine that. Our Universe exists of something that we can not see or measure.

But Dark stuff is ever expanding. It starts with Dark Matter then has evolved to include Dark Energy, Dark Galaxies, Dark Collisions and now Dark Flow.

newscientist.com - Orion's dark secret: Violence shaped the night sky

WHERE will astronomers stop in their love affair with the enigmatic substance called dark matter? First we were told it was essential to allow a galaxy to spin without falling apart. Then it was the glue that held clusters of galaxies together. Later it was said to have catalysed the formation of the galaxies in the first place. Now, surely, they have gone too far. If the latest theories pan out, dark matter has also given us some of the world's most enduring astrological myths...

That lack of success set astrophysicists thinking. What is the one thing that astronomers cannot see but are nevertheless convinced exists in vast quantities? Dark matter, of course....

Though there is no doubt in most astronomers' minds that dark matter exists, the evidence remains circumstantial. No one has directly detected a single particle of the stuff, and we are not even sure what it is made of. According to the leading theory, it is composed of particles called neutralinos. These hypothetical particles do not interact with passing light rays, but they are expected to unleash gamma rays if two happen to collide with each other.
newscientist.com - Orion's dark secret: Violence shaped the night sky

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Dark Collisions and Gould's Belt

Gould's belt

In the middle of the 19th century, the English astronomer John Herschel noticed that we are surrounded by a ring of bright stars. But it was Boston-born Benjamin Gould who brought this to wider attention in 1874. Gould's belt, as it is now known, supplies bright stars for many famous constellations including Orion, Scorpius and Crux, the Southern Cross...

It is a sizeable structure, some 3000 light years across, and can be traced as a bright band of stars tilted at about 20 degrees to the Milky Way. Within it are several thousand high-mass stars as well as up to a million low-mass ones. Most importantly, these stars appear to have formed separately from the rest of the stars in the galaxy - and that's what makes them so interesting.

Stars do not form randomly in the Milky Way. Instead they are confined to the arms that spiral around its nucleus...

"Gould's belt is not part of the spiral structure," says Fernando Comerón of the European Southern Observatory in Garching, Germany, who has been studying the belt for more than 30 years. "It must have been triggered by some local, violent event." But what caused that event?
Orion's dark secret: Violence shaped the night sky

Dark Collisions

Every galaxy is thought to be surrounded by a giant sphere of dark matter more than 10 times the width of the visible portion of the galaxy, and containing at least 10 times the mass of the visible stars. The dark matter "halo" is clumpy rather than smooth, because it contains residues of smaller halos that the galaxy has swallowed to grow to its present size. These clumps are referred to as the "halo substructure", and there are usually plenty of them.

"Count them all and you get a huge number," says Jürg Diemand who runs high-resolution supercomputer simulations of the Milky Way's halo substructure at the University of California, Santa Cruz. He estimates that in the halo surrounding the Milky Way - which is a pretty typical sort of galaxy - there could be a million billion (1015) such clumps of dark matter.

Crucially, this substructure is remarkably durable. Inside the halo, clumps of ordinary matter tend to radiate energy away, and this allows them to settle onto the disc of the galaxy. Dark matter clumps do not normally emit radiation, and so continue to circulate in the same orbits into which they were born - and this means that from time to time a clump of dark matter will come crashing through the disc of the Milky Way.
Dark collisions

For Kenji Bekki of the University of New South Wales in Sydney, Australia, this line of thinking was encouragement enough to set to work. He cranked up a computer model and began simulating what happened as clump after clump of dark matter smashed into one giant molecular cloud after another. Sure enough, he found that it was child's play to generate something resembling a Gould's belt. "The tilt is easy to reproduce," he says. "These collisions may be entirely natural.

Bekki's simulation shows that as a clump of dark matter with a mass of about 10 million suns passes through a giant molecular cloud, it pulls gas in towards the centre of the collisions and triggers a wave of star formation. As it continues through to the other side, it tilts the cloud and sets it spinning, as observed in Gould's belt (Monthly Notices of the Royal Astronomical Society: Letters, vol 398, p L36).
Orion's dark secret: Violence shaped the night sky

Childs play

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Massive "Dark Halo" Discovered Beyond Edge of the Milky Way

The biggest things in the universe just got bigger - or rather, they've always been bigger and we somehow missed it up to now.  Supercomputer simulations of galactic core black holes indicate that instead of being a mere two billion times the mass of the sun, so insignificant you'd surely lose them if you sneezed, some could be as large as six billion suns -not including the "dark halo" that surrounds the Milky Way, which is more than ten times as much mass as all of the visible stars, gas, and dust in the rest of the galaxy.

The study by scientists at the Max Planck Institute for Extraterrestrial Studies (which couldn't sound smarter if it was Lex Luthor's university degree) focused on Messier 87, a particularly bright active galaxy in the Virgo cluster whose size, strong signals and proximity to Earth make it a common astronomical experimentation subject.  Dr Karl Gebhart and colleagues ran a supercomputer simulation to calculate the mass of the monster at M87's core.

You need to simulate a black hole's size because there's no way to observe its mass directly - you can only infer its immensity by studying the effects on the mass around it (little things like entire galaxies).  Where the new model differs from past efforts is its inclusion of the "dark halo", an unobservable ring of dark matter which astrophysicists now believe surround galaxies.  Including something you can't see might sound like a great way to get any answer you like, but the simulation worked it out by observing the effects of this halo on the visible stars, then accounting for those calculated effects when simulating the black hole - which is why the program took several days to run on a computer that could probably calculate you to ten decimal places in one minute.

The dark matter halo is the single largest part of the Milky Way, covering the space between 100,000 light-years to 300,000 light-years from the galactic center. It is now believed that about 95% of the Galaxy is composed of dark matter, which does not seem to interact with the rest of the Galaxy's matter and energy in any way except through gravity. The dark matter halo is more than ten times as much mass as all of the visible stars, gas, and dust in the rest of the galaxy. While the luminous matter we see in the night skymakes up approximately 90,000,000,000 solar masses, he dark matter halo is believed to include around 600,000,000,000 to 3,000,000,000,000 solar masses of dark matter.

Don't worry, the results aren't entirely dependent on the dark matter magic-factor which affects so much of current cosmology - the results seem to explain observations which previously puzzled many scientists (always a good sign for a new result).  Recordings of distant quasars show evidence of black holes far larger than anything we've ever seen closer to home.  Now it seems that they were here all along, we just weren't looking at them right.
Massive "Dark Halo" Discovered Beyond Edge of the Milky Way

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Amazing. dark matter perhaps makes up 80% of the mass of the universe, yet we might have just perhaps detected it for the first time. 1 in 4 chance but worth an article. keeps someone in a job, career and pension.

Dark matter may have been "felt" for the first time deep in a Minnesota mine, physicists say.

Detectors in the mine, part of the Cryogenic Dark Matter Search experiment, were tripped recently by what might be weakly interacting massive particles, or WIMPs.

WIMPs are among the most popular candidates for dark matter, the invisible material that scientists think makes up more than 80 percent of the mass in the universe.

Recently detectors in the mine recorded two hits with "characteristics consistent with those expected from WIMPs," according to a statement posted on the Cryogenic Dark Matter Search Web site.

There is a one-in-four chance, however, that the particles detected are not dark matter but ordinary subatomic particles such as neutrons, the team cautions. (Related: "Dark Matter Proof Found Over Antarctica?")

Mike Shull, an astrophysicist at the University of Colorado at Boulder, also urged restraint in interpreting the results.

"I regard this as interesting but very much an interim 'progress report' on a promising technique," said Shull, who did not participate in the research.

"I hope they've detected [WIMPs]," he added, "It's exciting if it's true."

WIMPS: Best Dark Matter Candidate?

Scientists have predicted that WIMPs can interact with normal atoms but only weakly and very rarely—hence the name.

When such an interaction happens, a WIMP careens like a billiard ball off an atom, the theory goes. But the collision leaves behind a unique signature in the form of a small amount of heat, which can be detected.

The smashup also creates charged atoms, or ions, that are detectable.

The Cryogenic Dark Matter Search experiment uses 30 detectors made of germanium and silicon crystals.

The detectors were placed a half-mile (0.8 kilometer) underground at the Soudan mine, a defunct iron mine in northern Minnesota. The deep location helps block "background noise" from other particles, such as solar and cosmic rays.

Aside from the online statement, details on the new detections have yet to be published, and members of the Cryogenic Dark Matter Search team are declining comment.

But University of Chicago theorist Craig Hogan said that while the new detections are exciting, "it's not time for the champagne bottles yet."

The real significance of the apparent find would be that it could be used to help shape future dark matter detectors, which will be more sensitive and can better rule out false hits, Hogan said.

"It's not a discovery yet, but if these detections are real, we can turn it into a discovery."

Dark Matter Origins

If WIMP detections are confirmed by other experiments, then scientists will likely want to know where the particles are coming from, the University of Colorado's Shull added.

That's because the origins of dark matter particles passing Earth could help solve other cosmic mysteries.

Some theories of galaxy formation, for instance, say that our Milky Way and other "adult" galaxies are enveloped by halos of dark matter that are densest in the galactic centers.

If this is correct, Shull said, then dark matter particles would be expected to originate from the center of the Milky Way more often than from other regions of space.

Dark Matter Detected for First Time? - news.nationalgeographic .com

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Survey gets a grip on dark energy

Astronomers have measured the precise distance to over a quarter of a million galaxies to gain new insights into a key period in cosmic history.

The 3D map of the sky allows scientists to probe the time six billion years ago when dark energy became the dominant influence on the Universe's expansion.

No-one knows the true nature of this repulsive force, but the exquisite data in the international BOSS survey will help test various theories.

Preferred separation

The discovery that everything in the cosmos is moving apart at a faster and faster rate was one of the major breakthroughs of the 20th Century.

It went against all preconceptions. Up until the discovery, it was thought the Universe's expansion would most likely have been decelerating under the influence of gravity.

Scientists now find themselves grasping for new physics to try to explain what is going on.
Survey gets a grip on dark energy | bbc.co.uk

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Normal science and theory explains 4% of the whole universe but the original theories it is based on can not be wrong, the (gravity) universe has to be wrong. So lets create 96% of the whole universe that can not be seen or measured to explain that 4%. Very empirical and scientific.

Perhaps something else could explain it? Perhaps it is an Electric Universe?

The Fermi space telescope, designed to catch gamma rays, has seen hints of evidence for dark matter in high-energy gamma rays seen at the galaxy's centre.

The Fermi team is now opening a call for ideas on changing how it observes.

That may focus efforts on those early hints, opening the possibility to solve one of physics' greatest mysteries.

We only know of the existence of dark matter because of its gravitational effects; true to its name, it cannot be seen because it interacts only very weakly with light or normal matter.

Dark energy and dark matter mysteries
* Gravity acting across vast distances does not seem to explain what astronomers see
* Galaxies, for example, should fly apart; some other mass must be there holding them together
* Astrophysicists have thus postulated "dark matter" - invisible to us but clearly acting on galactic scales
* At the greatest distances, the Universe's expansion is accelerating
* Thus we have also "dark energy" which acts to drive the expansion, in opposition to gravity
* The current theory holds that 75% of the Universe is dark energy, 21% is dark matter, and just 4% the kind of matter we know well

"The nice fact which distinguishes this situation from other similar situations with dark matter candidates is that there are no viable astrophysical alternatives," said Lars Bergstrom, who first proposed this idea in a paper in Physical Review D in 1988.

"It is a so-called 'smoking gun' signal of dark matter annihilation," Prof Bergstrom told the BBC.
Fermi telescope may change to dark matter hunting | bbc.co.uk