Tag Archives: dark matter

Rethinking Dark Matter

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New model replaces dark energy theory with magnetic forces

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New model replaces dark energy theory with magnetic forces

It has been long believed that 70 percent of the universe is composed of dark energy, which makes it expand at an ever-increasing rate. However, a new model by researchers from the University of Copenhagen (UCPH) suggests that the expansion is due to a dark substance with a magnetic force, indicating that dark energy does not exist.

For many years, scientists have believed that 70 percent of the ever-accelerating, expanding universe is due to dark energy. The mechanism has been associated with an unknown repellant cosmic power called a cosmological constant, developed by Albert Einstein in 1917.

However, scientists cannot directly measure the cosmological constant, so a number of researchers, including Einstein himself, have begun doubting its existence, without suggesting a feasible alternative.

Now, a new study by UCPH researchers presented a model that replaces dark energy with a dark substance in the form of magnetic forces.

“If what we discovered is accurate, it would upend our belief that what we thought made up 70 percent of the universe does not actually exist,” explained Steen Harle Hansen, an associate professor at the Niels Bohr Institute’s DARK Cosmology Center.

“We have removed dark energy from the equation and added in a few more properties for dark matter. This appears to have the same effect upon the universe’s expansion as dark energy.”

The common understanding of how the universe’s energy is distributed is that it has five percent normal matter, 25 percent dark matter, and 70 percent dark energy.

However, in this new model, the 25 percent share of dark matter is given special qualities that make the 70 percent share of dark energy unnecessary.

dark-matter-04-01-2021

Image: Dark matter, which is invisible to the naked eye, illustrated with a blue color. Credit: NASA

“We don’t know much about the dark matter other than that it is a heavy and slow particle. But then we wondered— what if the dark matter had some quality that was analogous to magnetism in it?” said researcher Steen Hansen.

“We know that as normal particles move around, they create magnetism. And, magnets attract or repel other magnets– so what if that’s what’s going on in the universe? That this constant expansion of dark matter is occurring thanks to some sort of magnetic force?”

Hansen’s question served as the new model’s foundation, so the team developed it from the assumption that dark matter particles have some sort of a magnetic force. They then investigated the effect this force would have on the universe.

“It turns out that it would have exactly the same effect on the speed of the university’s expansion as we know from dark energy,” said Hansen.

“Honestly, our discovery may just be a coincidence. But if it isn’t, it is truly incredible. It would change our understanding of the universe’s composition and why it is expanding.”

“As far as our current knowledge, our ideas about dark matter with a type of magnetic force and the idea about dark energy are equally wild. Only more detailed observations will determine which of these models is the more realistic. So, it will be incredibly exciting to retest our result.”

Reference

“Consistency analysis of a Dark Matter velocity dependent force as an alternative to the Cosmological Constant” – Loeve, K., et al. – Cosmology and Nongalactic Astrophysics – arXiv:2102.07792

Abstract

A range of cosmological observations demonstrate an accelerated expansion of the Universe, and the most likely explanation of this phenomenon is a cosmological constant. Given the importance of understanding the underlying physics, it is relevant to investigate alternative models. This article uses numerical simulations to test the consistency of one such alternative model. Specifically, this model has no cosmological constant, instead the dark matter particles have an extra force proportional to velocity squared, somewhat reminiscent of the magnetic force in electrodynamics. The constant strength of the force is the only free parameter. Since bottom-up structure formation creates cosmological structures whose internal velocity dispersions increase in time, this model may mimic the temporal evolution of the effect from a cosmological constant. It is shown that models with force linearly proportional to internal velocites, or models proportional to velocity to power three or more cannot mimic the accelerated expansion induced by a cosmological constant. However, models proportional to velocity squared are still consistent with the temporal evolution of a Universe with a cosmological model.

Featured image credit: NASA

https://watchers.news/2021/04/01/new-model-replaces-dark-energy-theory-with-magnetic-forces/

Whole Lotta Untangling to Do

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The Universe May Be Flooded with a Cobweb Network of Invisible Strings

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We may soon find out whether we live in an axiverse

an abstract image of axion strings

(Image: © Shutterstock)

What if I told you that our universe was flooded with hundreds of kinds of nearly invisible particles and that, long ago, these particles formed a network of universe-spanning strings?

It sounds both trippy and awesome, but it’s actually a prediction of string theory, our best (but frustratingly incomplete) attempt at a theory of everything. These bizarre, albeit hypothetical, little particles are known as axions, and if they can be found, that would mean we all live in a vast “axiverse.”

The best part of this theory is that it’s not just some physicist’s armchair hypothesis, with no possibility of testing. This incomprehensibly huge network of strings may be detectable in the near future with microwave telescopes that are actually being built.

If found, the axiverse would give us a major step up in figuring out the puzzle of … well, all of physics.

A symphony of strings

OK, let’s get down to business. First, we need to get to know the axion a little better. The axion, named by physicist (and, later, Nobel laureate) Frank Wilczek in 1978, gets its name because it’s hypothesized to exist from a certain kind of symmetry-breaking. I know, I know — more jargon. Hold on. Physicists love symmetries — when certain patterns appear in mathematics.

There’s one kind of symmetry, called the CP symmetry, that says that matter and antimatter should behave the same when their coordinates are reversed. But this symmetry doesn’t seem to fit naturally into the theory of the strong nuclear force. One solution to this puzzle is to introduce another symmetry in the universe that “corrects” for this misbehavior. However, this new symmetry only appears at extremely high energies. At everyday low energies, this symmetry disappears, and to account for that, and out pops a new particle — the axion.

Now, we need to turn to string theory, which is our attempt (and has been our main attempt for 50-odd years now) to unify all of the forces of nature, especially gravity, in a single theoretical framework. It’s proven to be an especially thorny problem to solve, due to a variety of factors, not the least of which is that, for string theory to work (in other words, for the mathematics to even have a hope of working out), our universe must have more than the usual three dimensions of space and one of time; there have to be extra spatial dimensions.

These spatial dimensions aren’t visible to the naked eye, of course; otherwise, we would’ve noticed that sort of thing. So the extra dimensions have to be teensy-tiny and curled up on themselves at scales so small that they evade normal efforts to spot them.

What makes this hard is that we’re not exactly sure how these extra dimensions curl up on themselves, and there’s somewhere around 10^200 possible ways to do it.

But what these dimensional arrangements appear to have in common is the existence of axions, which, in string theory, are particles that wind themselves around some of the curled-up dimensions and get stuck.

What’s more, string theory doesn’t predict just one axion but potentially hundreds of different kinds, at a variety of masses, including the axion that might appear in the theoretical predictions of the strong nuclear force.

Silly strings

So, we have lots of new kinds of particles with all sorts of masses. Great! Could axions make up dark matter, which seems to be responsible for giving galaxies most of their mass but can’t be detected by ordinary telescopes? Perhaps; it’s an open question. But axions-as-dark-matter have to face some challenging observational tests, so some researchers instead focus on the lighter end of the axion families, exploring ways to find them.

And when those researchers start digging into the predicted behavior of these featherweight axions in the early universe, they find something truly remarkable. In the earliest moments of the history of our cosmos, the universe went through phase transitions, changing its entire character from exotic, high-energy states to regular low-energy states.

During one of these phase transitions (which happened when the universe was less than a second old), the axions of string theory didn’t appear as particles. Instead, they looked like loops and lines — a network of lightweight, nearly invisible strings crisscrossing the cosmos.

This hypothetical axiverse, filled with a variety of lightweight axion strings, is predicted by no other theory of physics but string theory. So, if we determine that we live in an axiverse, it would be a major boon for string theory.

A shift in the light

How can we search for these axion strings? Models predict that axion strings have very low mass, so light won’t bump into an axion and bend, or axions likely wouldn’t mingle with other particles. There could be millions of axion strings floating through the Milky Way right now, and we wouldn’t see them.

But the universe is old and big, and we can use that to our advantage, especially once we recognize that the universe is also backlit.

The cosmic microwave background (CMB) is the oldest light in the universe, emitted when it was just a baby — about 380,000 years old. This light has soaked the universe for all these billions of years, filtering through the cosmos until it finally hits something, like our microwave telescopes.

So, when we look at the CMB, we see it through billions of light-years’ worth of universe. It’s like looking at a flashlight”s glow through a series of cobwebs: If there is a network of axion strings threaded through the cosmos, we could potentially spot them.

In a recent study, published in the arXiv database on Dec. 5, a trio of researchers calculated the effect an axiverse would have on CMB light. They found that, depending on how a bit of light passes near a particular axion string, the polarization of that light could shift. That’s because the CMB light (and all light) is made of waves of electric and magnetic fields, and the polarization of light tells us how the electric fields are oriented — something that changes when the CMB light encounters an axion. We can measure the polarization of the CMB light by passing the signal through specialized filters, allowing us to pick out this effect.

The researchers found that the total effect on the CMB from a universe full of strings introduced a shift in polarization amounting to around 1%, which is right on the verge of what we can detect today. But future CMB mappers, such as the Cosmic Origins Explorer, Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD), and the Primordial Inflation Explorer (PIXIE) , are currently being designed. These futuristic telescopes would be capable of sniffing out an axiverse. And once those mappers come online, we’ll either find that we live in an axiverse or rule out this particular prediction of string theory.

Either way, there’s a lot to untangle.

Paul M. Sutter is an astrophysicist at The Ohio State University, host of Ask a Spaceman and Space Radio, and author of Your Place in the Universe.

from:    https://www.livescience.com/universe-filled-with-axion-strings.html

Where is the Dark Matter?

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Astronomy

19 more galaxies mysteriously missing dark matter have been found

The newly found outliers defy ideas of how these star systems evolve

NGC 5477
Most dwarf galaxies, like NGC 5477 seen in this image from the Hubble Space Telescope, have far more dark matter than normal everyday matter. But researchers recently found 19 dwarf galaxies that seem to be missing huge stores of dark matter.   Hubble/ESA and NASA

By Christopher Crockett

A smattering of small galaxies appear to be missing a whole lot of dark matter.

Most of a typical galaxy is invisible. This elusive mass, known as dark matter, seems to be an indispensable ingredient for creating a galaxy — it’s the scaffolding that attracts normal matter — yet reveals itself only as an extra gravitational tug on gas and stars.

But now, researchers have found 19 dwarf galaxies — all much smaller than the Milky Way — that defy this common wisdom. These newly identified outliers have much less dark matter than expected. The finding, published November 25 in Nature Astronomy, more than quintuples the known population of dark-matter renegades, adding fuel to an already simmering mystery.

“We are not sure why and how these galaxies form,” says Qi Guo, an astrophysicist at the Chinese Academy of Sciences in Beijing. Typical dwarf galaxies concentrate dark matter far more than their larger cousins, she notes. Their smaller size leads to weaker gravity, which has trouble holding on to tenuous clouds of gas. That usually shifts the balance of mass in dwarf galaxies away from normal matter and toward dark matter.

“This new class of galaxy is straining our ability to explain all galaxies in one cohesive framework,” says Kyle Oman, an astrophysicist at Durham University in England who was not involved in this research.

In 2016, Oman and his colleagues identified two galaxies that appeared to be missing dark matter. In short order, two more oddballs turned up (SN: 3/28/18).

Guo and her colleagues wondered if these galaxies had more company. So using existing data from the Arecibo radio telescope in Puerto Rico, the team weighed dwarf galaxies by looking at how fast hydrogen whipped around each one. Higher speed means more total mass. The researchers then combined the mass of the hydrogen and of all the stars, inferred from starlight, to estimate how much of each galaxy’s mass is made up of normal matter.

For every galaxy, total mass added up to more than the mass of the gas and stars — not surprising, as that extra mass is the dark matter. But in about 6 percent of cases, there wasn’t as much extra mass as expected.

One oddball, designated AGC 213086, weighs in at around 14 billion suns. If it were typical, about 2 percent of its mass — nearly 280 million solar masses — would be gas and stars. Instead, its actual inventory of normal matter is about 3.8 billion solar masses, or about 27 percent of its total mass.

Of 324 dwarf galaxies analyzed, 19 appear to be missing similarly large stores of dark matter. Those 19 are all within about 500 million light-years of Earth, and five are in or near other groups of galaxies. In those cases, the researchers note, perhaps their galactic neighbors have somehow siphoned off their dark matter. But the remaining 14 are far from other galaxies. Either these oddballs were born different, or some internal machinations such as exploding stars have upset their balance of dark matter and everyday matter, or baryons.

It may not be a case of missing dark matter, says James Bullock, an astrophysicist at the University of California, Irvine. Instead, maybe these dwarf galaxies have clung to their normal matter — or even stolen some — and so “have too many baryons.” Either way, he says, “this is telling us something about the diversity of galaxy formation…. Exactly what that’s telling us, that’s the trick.”

from:    https://www.sciencenews.org/article/19-more-galaxies-mysteriously-missing-dark-matter-found

THe Universe Just Keeps getting Bigger

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Scientists Find Dozens of ‘Invisible’ Galaxies, Changing Our Understanding of the Universe

Astronomers have discovered a stunning set of 39 massive galaxies that had previously been invisible.

ELIAS MARAT

Invisible Galaxies Universe

(TMU) — Using the combined power of multiple astronomical observatories across the world, astronomers have discovered a stunning set of 39 massive galaxies that had previously been invisible.

The multiple discovery is the first of its kind, according to a study published on Wednesday in Nature, and is set to forever change the way in which scientists look at how galaxies are formed.

The galaxies, which are located billions of light-years away, are intimately connected with supermassive black holes and the distribution of dark matter.

In a press release, lead researcher Tao Wang at the University of Tokyo said:

“This is the first time that such a large population of massive galaxies was confirmed during the first 2 billion years of the 13.7-billion-year life of the universe. These were previously invisible to us … This finding contravenes current models for that period of cosmic evolution and will help to add some details, which have been missing until now.”

And while the Hubble Space Telescope has allowed astronomers to gain major insights into previously unknown parts of the universe, the research team from the University of Tokyo relied on the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile to uncover this latest massive find.

And it appears that the huge galaxies would overwhelm our humble view of the heavens if they were actually visible to us humans. Given the age and distance of the huge galaxies, they have always been hidden from our view thanks to the weak and stretched light emanating from them. As a result of such distance, the visible light becomes infrared.

Kotaro Kohno, the study’s author and a professor at the University of Tokyo, explained:

“The light from these galaxies is very faint with long wavelengths invisible to our eyes and undetectable by Hubble.

So we turned to the Atacama Large Millimeter/submillimeter Array (ALMA), which is ideal for viewing these kinds of things. I have a long history with that facility and so knew it would deliver good results.”

The infrared light from the distant galaxies was originally revealed by the NASA Spitzer Space Telescope before ALMA’s “sharp eyes” detected them, cutting through the thick dust that obscured them from our sight, Wang explained.

“It took further data from the imaginatively named Very Large Telescope in Chile to really prove we were seeing ancient massive galaxies where none had been seen before.”

The new discovery will also shed light on the existence of supermassive black holes. Professor Kohno explained:

“The more massive a galaxy, the more massive the supermassive black hole at its heart. So the study of these galaxies and their evolution will tell us more about the evolution of supermassive black holes, too.

Massive galaxies are also intimately connected with the distribution of invisible dark matter. This plays a role in shaping the structure and distribution of galaxies. Theoretical researchers will need to update their theories now.”

So what would the sky look like if we happened to live in one of these ancient, massive galaxies? Wang explained:

“For one thing, the night sky would appear far more majestic. The greater density of stars means there would be many more stars close by appearing larger and brighter … But conversely, the large amount of dust means farther-away stars would be far less visible, so the background to these bright close stars might be a vast dark void.”

Wang is sure that in the future, new space-based telescopic technology will be able to reveal the chemicals, number of stars and basic composition of the dozens of galaxies that have been revealed. He explained:

“Previous studies have found extremely active star-forming galaxies in the early Universe, but their population is quite limited.

Star formation in the dark galaxies we identified is less intense, but they are 100 times more abundant than the extreme starbursts. It is important to study such a major component of the history of the Universe to comprehend galaxy formation.”

By Elias Marat | Creative Commons | TheMindUnleashed.com

from:   https://themindunleashed.com/2019/08/invisible-galaxies-universe.html

On Dark Matter

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Dark Matter Could Be Evidence of a Parallel Universe, Scientist Claims

  • Jun 13, 20199
(TMU) — One of the greatest mysteries in the universe is dark matter, which represents five times more matter than ordinary matter. At least, that is the ratio in our universe. An outlandish new theory suggests our physical reality may be attached at the hip to a parallel, mirror-image universe with inverse quantities of matter to dark matter.

The stunning theory is meant to resolve a seemingly intractable conundrum: one of the most pervasive substances in the universe—and that which binds galaxies together and makes it possible for life to exist—can’t be explained by modern physics. There is no shortage of scientists claiming to have theoretical explanations for dark matter, though, and now physicist Leah Broussard and her team of researchers are offering a mind-boggling solution to the question that doubles-down on the mystery: our universe is connected to a mirror-image alternate universe with its own molecules, galaxies, and life forms.

The theory resulted from new experiments with neutrinos that seem to suggest some particles can phase back and forth between our universe and the mirror-image universe. This could explain the anomalous neutron decay rate, which does not seem to produce as many protons as it should. Broussard posits that the reason for this violation of parity and symmetry is that 1 in 100 neutrons is being shared with the mirror universe.

The concept of dark matter producing its own parallel universe—which may contain its own dark matter life forms—is not new, but for the first time researchers will conduct an experiment that could offer proof.

Broussard says she plans to conduct an experiment that will involve firing high-speed neutrons at an “impenetrable” wall and measuring if any of them phase through. If the experiments produce evidence of a parallel universe, according to Broussard, “The implications would be astounding,” and could offer explanations of anti-matter, dark matter—which could be a gravitational force spilling over from the mirror universe—and the ever-elusive question of whether there are alternate universes.

However, such a mirror-universe would be different from many other depictions of alternate universes—including the type 1 multiverse, which is essentially just an endless universe where configurations of matter inevitably get repeated. It may even be different than a type 2 bubble multiverse, although Broussard describes it in similar terms, “It would form a bubble of reality nestling within the fabric of space and time alongside our own familiar universe, with some particles capable of switching between the two.”

This would suggest that universes may be inextricably interwoven, their realities and particles intertwined. It makes one wonder: What else might we be sharing with our mirror-universe? What else crosses over?

By Jake Anderson | Creative Commons | TheMindUnleashed.com

from:   https://themindunleashed.com/2019/06/dark-matter-parallel-universe.html

Dark Energy On the Rise

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The universe’s dark energy may be growing stronger with time, study suggests

, USA TODAYPublished 10:42 p.m. ET Jan. 31, 2019 | Updated 6:14 a.m. ET Feb. 1, 2019

While we aren’t really sure what dark matter and dark energy are, the final data released from ESA’s Planck mission confirms it apparently does exist. Buzz60

Dark energy, a mysterious invisible force believed to play a role in how the universe expands, may be growing stronger over time, according to a new study.

Dark energy, discovered 20 years ago by scientists measuring the distances to supernovas, or exploding stars, is described as an energy of empty space that never changes over space and time. Researchers believe it represents about 70 percent of the total universe.

The study published this week in the peer-reviewed British journal Nature Astronomyinstead measures the distances to quasars, bright celestial objects located in the center of galaxies.

Using data from NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton observatory, researchers found the expansion rate of the universe is different from the model using supernovas.

“We observed quasars back to just a billion years after the Big Bang, and found that the universe’s expansion rate up to the present day was faster than we expected,” Guido Risalti, a study co-author from the department of physics and astronomy at the University of Florence in Italy, said in a statement. “This could mean dark energy is getting stronger as the cosmos grows older.”

Elisabeta Lusso of Durham University in the United Kingdom said because this technique for assessing dark energy is new, researchers took extra steps to make sure it was a reliable way to measure. “We showed that results from our technique match up with those from supernova measurements over the last 9 billion years, giving us confidence that our results are reliable at even earlier times,” she said.

Researchers say they used quasars to measure because they have a much farther reach compared to supernovas.

Adam Riess, a professor of physics and astronomy at Johns Hopkins University, said while the discovery would be “a really big deal” if confirmed, quasars have not proven to be historically reliable.

“People have not really used them as precision measuring tools for the universe because they have a very large dynamic range,” said Riess. “We don’t have a lot of confidence when we see one, we know how luminous it ought to be.”

Robert Kirshner, a Clowes Research Professor of Science, Emeritus at Harvard University, said that while the results of the study could prove true, there is no other evidence to date showing dark energy has changed with time.

“The thing that’s attractive about (their work) is that quasars are brighter, so you can see them farther back,” said Kirshner. “But you do worry the quasars from the early universe are not quite the same as the ones nearby.”

from:    https://www.usatoday.com/story/tech/news/2019/01/31/dark-energy-mysterious-force-space-growing-stronger-study/2732772002/

Gravity & Dark Matter

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Dutch scientist publishes new theory of gravity

By Janene Pieters on November 8, 2016

Erik Verlinde

@erikverlinde / Twitter
University of Amsterdam scientist Erik Verlinde published a new theory of gravity which he debunks the existence of dark matter, NOS reports.

Astronomers often note in their observations that they observe more gravity in galaxies than the number of stars would suggest. This extra gravity is attributed to dark matter – an unknown substance believed to hold the galaxies together.

But in Verlinde’s new theory, he can calculate the movements of stars without including dark matter in the calculations. According to NOS, this is the first time that a scientist develop a theory that fits the observations of astronomers.

According to Verlinde, physisicsts are working on a revision on Einstein’s theory of relativity “Our current ideas about space, time and gravity urgently need to be re-thought. We have long known that Einstein’s theory of gravity can not work with quantum mechanics”, he said, according to NOS. “Our findings are drastically changing, and I think that we are on the eve of a scientific revolution.”

from:    http://nltimes.nl/2016/11/08/dutch-scientist-publishes-new-theory-gravity

Large Hadron Collector -Finding New Dimensions?

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Large Hadron Collider Could Detect Extra Dimensions

March 19, 2015 | by Stephen Luntz

Photo credit: Mopic via Shutterstock. If gravity is draining out of tiny black holes into other dimensions, the LHC may find it

A paper in Physics Letters B has raised the possibility that the Large Hadron Collider (LHC) could make a discovery that would put its previous triumph with the Higgs Boson in the shade. The authors suggest it could detect mini black holes. Such a finding would be a matter of huge significance on its own, but might be an indication of even more important things.

Few ideas from theoretical physics capture the public imagination as much as the “many-worlds hypothesis,” which proposes an infinite number of universes that differ from our own in ways large and small. The idea has provided great fodder for science fiction writers and comedians.

However, according to Professor Mir Faizal from the University of Waterloo, “Normally, when people think of the multiverse, they think of the many-worlds interpretation of quantum mechanics, where every possibility is actualized,” he said to Phys.org. “This cannot be tested and so it is philosophy and not science.” Nonetheless, Faizal considers the test for a different sort of parallel universes almost within our grasp.

“What we mean is real universes in extra dimensions,” says Faizal. “As gravity can flow out of our universe into the extra dimensions, such a model can be tested by the detection of mini black holes at the LHC.”

The idea that the universe may be filled with minute black holes has been proposed to explain puzzles such as the nature of dark matter. However, the energy required to create such objects depends on the number of dimensions the universe has. In a conventional four-dimensional universe, these holes would require 1016 TeV, 15 orders of magnitude beyond the capacity of the LHC to produce.

String theory, on the other hand, proposes 10 dimensions, six of which have been wrapped up so we can’t experience them. Attempts to model such a universe suggest that the energy required to make these tiny black holes would be a great deal smaller, so much so that some scientists believe they should have been detected in experiments the LHC has already run.

So if no detection, no string theory? Not according to Faizal and his co-authors. They argue that the models used to predict the energy of the black holes in a 10-dimensional universe have left out quantum deformation of spacetime that changes gravity slightly.

Whether this deformation is real is a rapidly developing question, but if it is, the paper argues that the black holes will have energy levels much smaller than in a four-dimensional universe, but about twice as large as that detectable for any test run so far. The LHC is designed to reach 14 TeV, but so far has only gone to 5.3 TeV, while the paper thinks the holes might be lurking at 11.9 TeV. In this case, once the LHC reaches its full capacity, we should find them.

Such a discovery would demonstrate the microscale deformation of spacetime, the existence of extra dimensions, parallel universes within them and string theory. If found at the right energy levels, the holes would confirm the team’s interpretation of a new theory on black hole behavior named gravity’s rainbow, after the influential novel. Such an astonishing quadruple revelation would transform physics, although the researchers are already considering the most likely flaws in their work if the holes prove elusive.

 

from:    http://www.iflscience.com/physics/large-hadron-collider-might-reveal-extra-dimensions

Of Gamma Ray Bubbles and Dark Matter

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MILKY WAY’S GAMMA RAY BUBBLES SHAPED BY DARK MATTER?

Amy Shira Teitel
Analysis by Amy Shira Teitel
Tue May 8, 2012 11:37 AM ET

Gamma-ray-bubbles

Dark matter, the elusive stuff that makes up a substantial portion of all the mass in the universe, is largely a mystery to astronomers. They’ve tried finding it and creating it, but so far no conclusive proof as to what exactly it is though most theories state that we interact with it through gravity.

But Christoph Weniger, of the Max Planck Institute for Physics in Munich, has a different theory to explain new possible evidence for dark matter. By carrying out statistical analysis of three and a half years worth of publicly available data from NASA’s Fermi Space Telescope, he’s found a gamma ray line across the sky that he says is a clear signature of dark matter.

Astrophysicists generally think that supermassive black holes, like the one at the center of the Milky Way, release jets that interact with surrounding dark matter. This interaction is thought to be the source of high-energy gamma rays that satellites like Fermi can detect. What satellites can see are the photons produced when these jets interact with dark matter.

Weniger looked for signs of such an interaction in about three and a half years worth of gamma-ray observations carried out by the Fermi satellite’s Large Area Telescope (LAT).

To increase his chances of success he only considered data from those regions of the Milky Way that should generate the highest ratios of dark-matter photons to photons from background sources. He was looking specifically for a peak in energy, a sign that a photon was produced by the collision between and annihilation of two particles; the photon left over should have the same mass as one dark matter particle. This energy would theoretically appear as a very narrow peak, a line in gamma-ray spectra, distinct from the broad energy distribution seen across the visible universe.

That’s just what he found — a line in the gamma ray spectrum.

But he’s quick to admit it’s a provisional result. His data points come from about 50 photons and he’ll need a lot more to prove conclusively that his line is related to dark matter. It’s possible the line he observed is from a known, though no less mysterious, astronomical phenomenon: the pair of enormous gamma-ray-emitting bubbles extending outwards from the plane of the Milky Way.

In December 2010, scientists working with the Fermi Space Telescope found two giant lobes extending from the black hole at the center of our galaxy.

Twenty-five thousand light years high, each bubble spans more than half of the visible sky reaching from the constellation Virgo to the constellation Grus and may be relatively young at just a million or so years old.

The bubbles are a recent find, normally masked by the fog of gamma rays that appears throughout the sky that is a result of particles moving near the speed of light interacting with light and interstellar gas in the Milky Way. Scientists only found the bubbles by manipulating the data from the LAT to draw out the striking feature.

The manipulated images show the bubbles have well defined edges, suggesting they were formed as a result of a large and relatively rapid energy release — the source of which is still unknown. Interestingly, the energy cutoff of the bubbles corresponds to the gamma ray line Weniger found, the one he’s associating with a dark matter signature.

It’s possible the bubbles and the line have the same origin. Or, dark matter might be the cause of the bubbles’ defined endpoint.

Whether or not the two observations turn out to be linked — which of course hinges on conclusive proof of Weniger’s gamma ray line — both are very cool and part of the fascinating and mystery nature of our corner of the universe.

Image credit: NASA-Goddard

from:   http://news.discovery.com/space/dark-matter-and-gamma-ray-lobes-light-up-the-visible-universe-120508.html