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Astronomers Have Captured The First Images of Dark Matter

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The known universe contains trillion of galaxies with billions of stars in it. Looking at the big picture, the galaxies in universe are connected to each other by an invisible web of dark matter. Due to some clever use of gravitational lensing these threads of dark matter are now captured for the first time.

Artist's impression of how the Dark Matter could have been like in very early Universe might have looked.

A team of astronomers at the University of Waterloo in Canada has seen the un-seeable using the space-bending effects of dark-matter to create a visual of their dark features by combining the catalogs of galaxy groups that act as lenses with catalogs of data on the light-sources behind them.

Interesting thing is that what we observe through telescope only makes the five percent of observable universe. Other 68 percent of it exists, is some sort of energy that pushes space apart at ever faster speeds. Since so little else is known about this, the cause is referred to as 'dark energy'.

We only know the effect of dark matter not its cause and it makes almost 27 percent of the observable universe. Dark matter is different. It makes up about 27 percent of the observable Universe; and like dark energy, we can see an effect without knowing much about what seems to be causing it.

First Image of Dark Matter. Dark matter filaments bridge the space between galaxies in this false color map. The locations of bright galaxies are shown by the white regions and the presence of a dark matter filament bridging the galaxies is shown in red. Credit: S. Epps/M. Hudson/University of Waterloo

Clumps of dark matter sit silently, making a bit of a dent in the surrounding fabric of the Universe but not responding to anything else. That effect is basically gravity. As most materials that have mass also seem to either emit or absorb electromagnetic radiation.

So far we are not able to calculate the exact mass there should be to account for the movements and positions of stars and galaxies.

According to the most accepted theories of the universe, dark energy is thought to contribute 73 percent of all the mass and energy in the universe. Another 23 percent is dark matter, which leaves only 4 percent of the universe composed of regular matter, such as stars, planets and people. Pie chart via NASA.

Through this we are able to analyze that old bright matter form clumps while more prevalent dark matter forms holes around the glowing gas and stars. That also means galaxies tend to settle along these threads, forming interconnected superclusters that stretch out in maps not just of space, but of time itself.

Knowing dark matter lies between visible galaxies on the cosmic web is one thing – actually seeing it is something else.

The curves and dimples that produces with the drifts of light caused effects of gravity. The threads of dark matter appear to be strongest between bunches of galaxies less than 40 million light-years apart.

Adding this high resolution to existing maps could finally reveal a few more enticing details about this very much mysterious form of matter and would tell us how Universe evolved.

The astronomers were able to use slight variations to build a relatively detailed map of the bridges of otherwise invisible dark matter connecting them, by combining various images of 23,000 pairs of galaxies about 4.5 billion light-years away.

Epps said: "By using this technique, we're not only able to see that these dark matter filaments in the universe exist, we're able to see the extent to which these filaments connect galaxies together."

Researcher Mike Hudson said: "For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together. This image moves us beyond predictions to something we can see and measure."

It'll just make us picture the Universe as a cosmic ball of sugar.

This research was published in Monthly Notices of the Royal Astronomical Society.

Missing Neutrons May Lead a Secret Life as Dark Matter

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Neutrons shouldn’t be all that mysterious. Found inside every atomic nucleus, they may seem downright mundane—but they have long confounded physicists who try to measure how long these particles can live outside of atoms. For more than 10 years researchers have tried two types of experiments that have yielded conflicting results. Scientists have struggled to explain the discrepancy, but a new proposal suggests the culprit may be one of the biggest mysteries of all: dark matter.

Scientists are pretty sure the universe contains more matter than the stuff we can see, and their best guess is that it takes the form of invisible particles. What if neutrons are decaying into these invisible particles ? This idea, put forward by University of California, San Diego, physicists Bartosz Fornal and Benjamin Grinstein in a paper posted this month to the physics preprint site arXiv.org, would explain why one type of neutron experiment consistently measures a different value than the other. If true, it could also provide the first way to access the dark matter particles physicists have long been seeking to no avail.

The idea has already gripped many researchers making neutron lifetime measurements, and some have quickly scrambled to look for evidence of it in their experiments. If neutrons are turning into dark matter, the process could also produce gamma-ray photons, according to Fornal and Grinstein’s calculations. “We have some germanium gamma-ray detectors lying around,” says Christopher Morris, who runs neutron experiments at Los Alamos National Laboratory. By serendipity, he and his team just recently installed a large tank to collect neutrons on their way from the start of the experiment to the point where physicists try to measure their lifetimes. This tank provided a large holding cell where many neutrons might decay into dark particles, if the process in fact occurs, and produce gamma-rays as a by-product. “When we heard about this paper, we took our detector and set it up next to our big tank and started looking for gamma rays.” He and his team are still analyzing the results of this trial, but hope to have a paper out in a few weeks reporting on what they found.

Only one of the two types of neutron decay experiments would be sensitive to neutrons decaying into dark matter. This type, called “bottle experiments,” essentially puts a given number of neutrons into a “bottle” with magnetic walls that holds them inside, then counts how many are left after a certain amount of time. Through many measurements the researchers can calculate how long an average neutron lives.

The other type of experiment looks for the main product of neutron decays. Through a well-known process called beta decay, a neutron outside of an atomic nucleus will break down into a proton, an electron and an antimatter neutrino. So-called “beam” experiments shoot a beam of neutrons into a magnetic trap that catches positively charged protons. Researchers count how many neutrons go in and how many protons come out after a given time, then infer the average time it takes a neutron to decay.

Both classes of experiments find neutrons can last for only about 15 minutes outside of atoms. But bottle experiments measure an average of 879.6 seconds plus or minus 0.6 second, according to the Particle Data Group, an international statistics-keeping collaboration. Beam experiments get a value of 888.0 seconds plus or minus 2.0 seconds. The 8.4-second difference may not seem like much, but it is larger than either of the calculations’ margins of error—which are based on the experimenters’ understanding of all the sources of uncertainty in their measurements. The difference leaves the two figures with a statistically significant “4-sigma” deviation. Experimenters behind both methods have scoured their setups for overlooked problems and sources of uncertainty, with no luck so far.

But if neutrons can transform in more ways than just beta decay, it would explain why bottle and beam experiments do not find the same answers. Fornal and Grinstein suggest that occasionally neutrons turn into some type of dark particle, undetectable by traditional means. The bottle experiments would then measure a slightly shorter lifetime for the neutron than beam experiments, because the former would be counting the dark matter decays in addition to the beta decays—and thus detecting a larger number of total decays in any given time period. The beam setup, however, only measures how long it takes neutrons to turn into protons, so their tally would not include dark matter decays and would therefore suggest neutrons can stick around slightly longer. And that is indeed what the two methods show.

“It would be nice to have an explanation,” says Peter Geltenbort, who runs bottle experiments at the Institut Laue–Langevin in France. If the dark particle idea is correct, “it means that we experimentalists are giving the right error for our measurements. People have written that maybe we are just too optimistic estimating our systematic [uncertainties], but it would confirm that we did a good job.” Geltenbort is also collaborating with Morris on the Los Alamos bottle experiments.

Perhaps the larger implication—if neutron experiments show any evidence for the dark particle hypothesis—is that physicists might then have a link to dark matter. The dark particle that Fornal and Grinstein propose could be the same particle that makes up the cosmos’ missing mass. It could also be a different invisible particle, perhaps part of some larger sector of numerous dark particles. “They [Fornal and Grinstein] are building a very specific set of models to explain the neutron lifetime discrepancy,” says dark matter theorist Peter Graham of Stanford University. “It’s not obvious that their models really fit into any other dark matter models that people have built for other reasons.” For the neutron to decay into a dark particle, for instance, that particle must be lighter than the neutron’s mass of around 940 MeV/c2 (mega–electron volts divided by the speed of light squared). On the other hand, one of the most popular classes of theorized dark matter particles, so-called weakly interacting massive particles (WIMPs), would weigh somewhere around 100 GeV/c2 (giga–electron volts divided by the speed of light squared)—roughly 100 times more than a neutron.

Article was published originally on Scientific American.

NASA Just Detected A Strange, Strong Signal From Deep Inside the Milky Way --"May Reveal the Dark Side of Our Universe"

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NASA’s Chandra X-Ray Observatory has observed very strange and distinctive X-ray signal coming from our Milky Way Galaxy that researchers believe can help them in proving the existence of the mysterious dark side of the universe. That is the claim of US scientists who analyzed the energy spectrum of X-rays.

The data was gathered by NASA’s Chandra satellite who found more X-ray photons with a particular energy than would be expected if they were generated by the decay of dark matter particles, say the researchers. This is not the first time that scientists have seen extra photons with an energy of about 3,500 electronvolts (3.5 keV) in the spectra recorded by X-ray satellites.

The researchers found that the strength of their 3.5 keV signal was consistent with data from NASA’s X-ray satellite, the Nuclear Spectroscopic Telescope Array (NuStar). With no obvious interference within the satellite itself, the researchers concluded that the signal is unlikely to be caused by instrumental noise.

"This result is very exciting," said Dr Abazajian, a cosmologist at the University of California, Irvine who was not involved in the research. "It makes it more likely that the line is due to dark matter, which makes up more than 80% of all the mass in the Universe. As its name suggests, it gives off no light, but reveals its presence through the gravitational pull it exerts on stars within galaxies.

The latest research, which targets relatively light particles of dark matter, has been carried out by Nico Cappelluti of the Yale Center for Astronomy and Astrophysics in Connecticut, US, and colleagues.

His colleague, Esra Bulbul of the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology (MIT) was the first scientist to spot an anomalous line at 3.5 keV, when looking at the X-ray spectra of large numbers of galaxy clusters in 2014. Researchers elsewhere have seen a line with the same energy in spectra from a variety of other objects, including the Andromeda and Milky Way galaxies, which are thought to be enveloped in a bubble of dark matter.

The researchers are heartened by the fact that four different satellites have now seen the same signal but are not ready to claim discovery of dark matter because, they say, it is still possible that their result is a statistical fluke - that the Chandra Observatory just happened to snare more X-rays with an energy of 3.5 keV than it did others.

"As we collect more and more X-ray data, the evidence for the 3.5 keV line is growing and growing," said Cappelluti.

Astrophysicists have been scanning the Milky Way for years for the photons generated when dark matter particles either annihilate with one another or decay. The so-called weakly-interacting massive particles (WIMPs) are believed by some researchers to be responsible for unusual emissions of gamma rays seen coming from the center of the Milky Way. While others think sources such as pulsars are probably the cause.

To establish whether dark matter could be the source, they compared Chandra's spectra to those of X-rays from the center of the Milky Way that had been detected by the European Space Agency's XMM-Newton satellite. As expected, they found the signal in the latter to be stronger, given that dark matter should be densest where there are more stars as found in the galactic center.

The researchers also ruled out a couple of alternative astrophysical sources for the signal: photons emitted either when very large black holes suck in material from their surroundings or when ions of sulphur take electrons from hydrogen in the centre of galaxy clusters. "We found that our result is consistent with previous results if you assume the cause to be dark matter," said Bulbul.

Others, however, urge caution. Dan Hooper, a particle theorist at Fermilab near Chicago, points out that a number of other studies have failed to see the line, including one by a group analysing data from the Japanese space agency's (Jaxa) ill-fated Hitomi X-ray satellite that malfunctioned just over a month after launch in February 2016, but managed to collect enough data to disprove a previously claimed sighting of the 3.5 keV line in the Perseus galaxy cluster.

"The new paper claims a modest detection," said Dr Hooper, "but it doesn't sway me very strongly at this point."

Christoph Weniger, a theoretical astroparticle physicist at the University of Amsterdam, is a little more upbeat, reorting to the BBC that the new research "adds yet another piece to the 3.5 keV puzzle".

He said that the signal might be due to a hypothetical particle known as the sterile neutrino, which would decay into an X-ray photon and a normal neutrino. But he stressed the need for more data to "confirm or reject the dark matter hypothesis".

Via DailyGalaxy

Scientists Just Found Half of the Missing Matter in Our Universe

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While teams of researchers continue the hunt for clues into the nature of elusive dark matter and dark energy, which comprise most of the known universe, other teams are trying to unravel the mysteries of so-called ordinary matter, which contains the protons, neutrons, and electrons with which we’re familiar.

While we can and have observed ordinary matter under a variety of circumstances, we have yet to actually see about half of what we know must be residing in the vast gaps between galaxies, stars, and other objects in space. This missing matter even accounts for much of our own Milky Way.

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However, two teams of astronomers have now released studies outlining how they may have found this previously unobserved matter. One study was undertaken by researchers at the Institute of Space Astrophysics (IAS) in Orsay, France, while the other team worked from the University of Edinburgh on their study. The two teams confirmed that the missing ordinary matter in the universe can be found in the form of filaments of hot, diffuse gas linking galaxies together.

While long predicted, these gasses have a tenuous nature that has made them impossible to detect using X-ray telescopes. To get around that, both teams made use of the Sunyaev-Zel’dovich effect. This phenomenon occurs when leftover light from the Big Bang passes through hot gas, leaving behind a trace of the gas that can be captured. A map of this effect within the observable universe was produced by the Planck satellite in 2015.

Using data from the Sloan Digital Sky Survey, each team chose pairs of galaxies supposedly connected by baryon strands. Then, to make the faint individual signals more visible, they stacked the Planck signals for these areas. The team at IAS combined 260,000 pairs of galaxies, while the Edinburgh team worked with more than a million pairs.

Their findings were similar. The IAS group found the baryon gasses to be three times denser than the normal mass of matter in the universe, while the other group observed them to be six times denser. In short, both found definitive evidence that the gas between the galaxies was dense enough to form filaments.

Galactic Pairs

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This discovery is a remarkable example of how new technologies can allow scientists to test theories made decades prior. As Harvard-Smithsonian Center for Astrophysics in Massachusetts professor Ralph Kraft, who wasn’t involved in the studies, told New Scientist:

“Everybody sort of knows that it has to be there, but this is the first time that somebody – two different groups, no less – has come up with a definitive detection. This goes a long way toward showing that many of our ideas of how galaxies form and how structures form over the history of the universe are pretty much correct.”

Beyond giving scientists the ability to throw around an “I told you so” or two, the discovery of this missing matter also has the potential to improve our current maps of the universe and inform future research. The more we learn about this world in which we live, the more we increase our ability to maneuver within it, perhaps one day reaching the very same distant galaxies studied by these groups of researchers.

References: New Scientist, arXiv, arXiv

New Research Suggests Dark Energy Might Be The Reason Time Runs Forward

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A new study may have found a link between dark energy and the Second Law of Thermodynamics—suggesting that the very expansion of the universe may impart a direction to time. It’s one of those things that we take for granted—time moves forward and never backward. But did you ever stop to wonder why it moves in one direction, as opposed to the other?

The question continues to stump physicists. After all, there are certain physical processes that are actually time-reversible—they look the same no matter which way you run them.

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For example, gravity operates the same way regardless of Time’s Arrow; a planet will orbit a star in exactly the same way, just with the direction of that orbit reversed. But there is one aspect of the universe that is dependent on the direction of Time’s Arrow: the Second Law of Thermodynamics. This states that the disorder of a closed system (such as our universe) must increase, never decrease.

It’s commonly called “entropy,” and it’s why broken eggs don’t suddenly reassemble themselves, or why dead things don’t suddenly come back to life. Disorganization and chaos are downhill, order and complexity are uphill; complex systems like stars and planets and human beings may emerge locally, but they require an inordinate amount of energy to create, which only increases the overall entropy of the system. This is why the Second Law of Thermodynamics is universally reckoned as the mechanism that imparts directionality to time—although, understanding the how of a thing is not the same as understanding the why of it.

A DARK CONNECTION: In the quest to understand the origins of Time’s Arrow, two Armenian physicists, A. E. Allahverdyan and V. G. Gurzadyan, decided to search for a link between so-called “dark energy” and the Second Law of Thermodynamics. Dark energy is a mysterious quantity that is proposed as an explanation for why the universe is continuing to expand, rather than decelerating and collapsing, as our current understanding of gravity dictates it should.

The scientists ran a simulation to test how the orbit of a planet would change, depending upon whether dark energy was absent, or present as in our own universe. What they found was intriguing, to say the least: if dark energy is absent, or if gravity pulls space together, a planet simply orbits its star in the accepted fashion, regardless of whether time runs “forward” or “backward.” But introduce dark energy to push space apart, and eventually, over immense time scales, the planet is flung away from the star altogether.

Which means there is a temporal directionality when dark energy is introduced—in one direction, we see a planet escaping a star’s gravity; in the other, a planet is captured by a star and becomes a part of its retinue. There’s nothing absolutely conclusive about the study, which was published in Physical Review E; the authors aren’t saying dark energy is responsible for Time’s Arrow. But there’s something decidedly suggestive about it all—that the Second Law of Thermodynamics and dark energy might be two facets of the same phenomenon, some mysterious quantity of our universe that imparts or requires an arrow of time.

So next time you’re late—just blame it on dark energy.

References: Science Alert - Latest

New Theory Disproves Dark Energy And Acceleration Of Universe Expansion

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The universe is constantly expanding and has held the fascination of every sci-fi fan. This is a phenomenon that has been baffling astrophysicists for years. A paper published in the journal Monthly Notices of the Royal Astronomical Society by a group at the University of Canterbury in Christchurch, New Zealand, has found that a universe with no dark energy — which is essential to prove that the expansion is an acceleration process — better fits the Ia (pronounced one-a) Supernova theory.

Dark energy is the mysterious void in space science. It is basically a theory formed to bridge gaps in our theory about what space is actually made up of, how it expands, and how the rate of this expansion is accelerating. It was theorized to help sustain current models of the universe, how it was formed and what it is made of.

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Dark energy is a theoretical energy that acts opposite to gravity and facilitates the acceleration of the expansion of the universe. It holds the exact values of all the holes in this theory. Meaning, it was created having the exact values to fill the gaps. It is like a balancing the steps in a wrong math problem to make it seem right.

Scientists say the universe is expanding based on the changes in perceived distance and the measured distance of supernova explosions in distant galaxies. The change in distance over time pointed to one thing only, expanding universe pushing the object away.

The previous two models that tried to explain this were both based on the simplified 100-year-old cosmic expansion law — Friedmann's equation. There were the standard Lambda Cold Dark Matter cosmology model and the other model which claimed that the universe was empty with the expansion neither accelerating nor decelerating. Both were based on this same equation.

This Friedmann's equation assumes that the new space created during the expansion is just empty, and theoretically, ideal. There are complicated interactions between galaxies. Friedmann's equation does not take into account this delicate cosmic balance that needs to be maintained to balance the intricacies of the primordial ‘soup.’

Prof David Wiltshire, who led the study from the University of Canterbury in Christchurch said:

"The past debate missed an essential point; if dark energy does not exist then a likely alternative is that the average expansion law does not follow Friedmann's equation."

This presupposing of one particular answer has held back alternate ways of looking at the expansion of the universe. In the newly proposed model is called 'timescape cosmology'. There is no dark energy here to fill the gaps.

This is because the dark energy is needed to explain to this model only if certain factors are taken into consideration. These factors are known as clocks. They are basically methods or angles of studying the expansion of the universe. Each model has a clock to explain the time line and the rate of expansion of the universe. The clocks determine from what perspective you view the universe and at what rate the universe is expanding from where you are standing.

What this means is, whether this uniform acceleration happens or not depends on which clock you use. So in this model, the clocks differ at different points of observation. In environments where matter density is found slightly different from volume averages, the clocks will differ.

So, what factors you take into account to explain the expansion differ at different points in the universe. Whether or not one infers accelerating expansion then rests critically on the clock used. This model includes perspective and position of observation into account and states that the expansion may not the uniformly accelerated process for every observer.

The timescape cosmology model was found to fit the data available from the largest supernova data catalog better than the existing lambda CDM model, said the study. This is the only way to test the model. The data available is not comprehensive enough to fuel any proof that this is the right way to study expansion. The European Space Agency's Euclid satellite, scientists in the study say, will have the power to distinguish between the standard cosmology and other models that have been proposed, and help scientists to decide whether dark energy is real or not.

What this theory does is challenge existing models with ideas that carry weight. Only when such challenges are made, are breakthroughs created. We could be on the cusp of major breakthroughs in the biggest question we have faced. The creationist dilemma deserves a conclusion.