Tag Archives: dark matter

Most Convincing Evidence Yet For Dark Matter Detection

Most Convincing Evidence Yet For Dark Matter Detection

Scientists have been analyzing high-energy gamma rays originating from the center of the Milky Way and have presented the most convincing case so far that at least some of this may come from dark matter.

Dark matter is a type of matter that is thought to account for apparent effects due to mass where no mass can be observed. It behaves differently to normal matter, such as planets and stars, which only accounts for approximately 5% of the universe. It neither emits nor absorbs light or other forms of electromagnetic energy, so a simple definition is that it is matter that does not react to light. The total mass-energy of the known universe is estimated to contain approximately 27% dark matter.

Using data collected from NASA’s Fermi Gamma-ray Space Telescope, scientists from different institutions generated maps of the center of the galaxy. They found that some of the high-energy gamma rays could not be sufficiently explained by known sources. There are numerous known sources of gamma-rays in the center of the galaxy, such as supernova remnants, but it is also predicted to be rich in dark matter. Although scientists know dark matter exists, they are not entirely sure of what it is composed of. Weakly Interacting Massive Particles, or WIMPs, are a strong candidate. It is thought that collision of WIMPs may produce a quickly decaying particle, which could produce gamma rays detectable by Fermi.

Once they removed all the known sources of gamma rays from the Fermi observations, some emission was leftover. If dark matter particles with a particular mass are destroying each other, this would be a remarkable fit for the remaining emission. Despite this, the scientists err on the side of caution since alternative sources may still exist. Further sightings are also required to make this interpretation more convincing.

The Fermi scientists have also turned elsewhere in an attempt to detect dark matter by looking at dwarf galaxies orbiting the Milky Way. Dwarf galaxies are rich in dark matter and lack other types of gamma-ray sources present in the center of the Milky Way which make detection of dark matter problematic. On the flip side, their distance from us and the fact that the dark matter present is still considerably less than that in the center of the Milky Way means that the signals are weak. But according to Elliott Bloom, a member of the Fermi collaboration, “If we ultimately see a significant signal, it could be a very strong confirmation of the dark matter signal claimed in the galactic center.”

While at this stage the signal cannot be confirmed or refuted as dark matter, it represents an exciting step towards the detection of dark matter at the galactic center. 

Check out this YouTube video for an image of the Milky Way with the gamma-ray map from NASA’s Fermi superimposed on top. 

Credit: NASA Goddard; A. Mellinger, CMU; T. Linden, University of Chicago

Read more: http://www.iflscience.com/space/most-convincing-evidence-yet-dark-matter-detection

Has The Smoking Gun For Dark Matter Been Found?

Has The Smoking Gun For Dark Matter Been Found?

The hunt for mysterious dark matter has so far produced very little results, but scientists might have found evidence of “dark matter annihilation,”essentially dark matter particles colliding and producing a signal.An American team of astronomers discovered the promising gamma-ray emission coming from within the halo of the Milky Way.

The source, 3FGL J2212.5+070, was found to be producing gamma-rays by NASA’s Fermi telescope. What’s unusual, though, is that this source is spread over a large regionor in other words, it is spatially extended. Other sources for gamma-rays, such as pulsars and black holes, are “point-like” and come from one place.

Found in a subhalo clump, a region of the outer part of the Milky Way,the source was also not detected at other wavelengths aside from gamma-rays, which makes it a great candidate for dark matter, ausually invisible substance. The findings have beensubmitted to the Journal of Cosmology and Astroparticle Physics, andare available onarXiv.

Extended objects that emit in gamma-rays also emit in radio, X-rays, and so on,lead author Dr. Bridget Bertoni told IFLScience.So, the fact that we found something that was emitting only in gamma-rays that was extended and had a spectrum that looked like a dark matter annihilation spectrum made this source an especially interesting dark matter subhalo candidate.

NASA’s Fermi telescope, illustrated, was used to make the discovery. NASA/Fermi

Dark matteris a mysterious type of matter that permeates the universe. Its six times more abundant than ordinary matter and it doesnt interact with light, hence the nickname dark. But wecan see the effect of dark matter on the shape of galaxies and how they are distributed in space.

Dark matter is thought to accumulate at the center of galaxies, so several searches have been conducted to look for signals from the core of the Milky Way. But while somepotential signals have beendetected, theres alot of debateon the nature of these sources.

We followed another way to search for this dark matter annihilation, complementary to searches in the galactic center, saidDr. Bertoni.We are looking at dark mattersubhalos.These are small bound clumps of dark matter that are in the Milky Way. It is predicted that there should be many small clumps of dark matter around galaxies such as the Milky Way.

Astronomers think that dark matter could be made by weakly interacting massive particles(WIMPs). When these particles collide, they are expected to emit gamma-raysthe signal of which could be observed by gamma-ray telescopes such as the Fermi telescope.

While the source is very promising, the researchers have discussed the possibility that the detection is not a single extended subhalo but two nearby gamma-ray sources. The model suggests that there isa 2 percent probability that a pair such as this would exist somewhere in the sky. The chance is small but not zero, and more observations are necessary to confirm its true nature.

It would be great to have other follow-up [observations] of this object, said Dr. Bertoni.What you would need are observations with a high angular resolution to distinguish if this is two objects or one object. Also, to continue to search for gamma pulsations coming from this object would be useful as well.

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Fast Dwarf Galaxy Generates Ripples In The Milky Way

Fast Dwarf Galaxy Generates Ripples In The Milky Way

The edge of the Milky Way is not smooth but has ripples, and these ripples have perplexed astronomers since their discovery decades ago. But now we know exactly what caused them.

An international team of astronomers discovered that a small and quick galaxy whizzed past the Milky Way a few hundred years ago. The scientists were able to measure the speed of some of the stars belonging to the dwarf galaxy, which allowed them to work out what actually happened when the fly-by occurred.

Its a bit like throwing a stone into a pond and making ripples, Sukanya Chakrabarti, who presented the findings at the227th meetingof the American Astronomical Society in Florida,said in a statement.Of course we arent talking about a pond, but our galaxy, which is tens of thousands of light-years across, and made of stars and gas, but the result is the same ripples!

Her work is part of a new discipline called galactoseismology, and just like geologists use earthquakes to study the interior of our planet, ripples and interactions allow astronomers to estimate the distribution of matter in a galaxy. This is really the first non-theoretical application of this field, where we can infer things about the unseen composition of galaxies from analyzing galaxic-quakes, said Chakrabarti.

The stars observed are called Cepheid variables, whichare one type of standard candle, objects whose distance can be calculated based on their luminosity.

We have a pretty good idea of the distance to these stars because the intrinsic brightness of Cepheid variable stars depends on their period of pulsation, which we can measure, said Chakrabarti.

What I wanted to know was how fast this speeding bullet was going when it passed by our galaxy with that information we can begin to understand the dynamics, and ultimately how much unseen dark matter is there.

Cepheid VariableRS Puppisas imaged by Hubble(HST).

Dark matter is the dominant type of matter in the universe (making up 84 percent of all matter), but it does not interact with light so we cannot see it. Its effects can be seen on large scales, for example keeping the spiral shape in galaxies or grouping clusters of galaxies in large filaments.

We are yet to directly observe dark matter, but Chakrabarti and her team are looking for more Cepheid variable stars in the halo of the Milky Way to estimate how much dark matter there is in our galaxy.

There could be a population of yet undiscovered Cepheid variables that formed from a gas-rich dwarf galaxy falling into our galaxys halo, said Chakrabarti.With the capabilities of todays telescopes and instruments we should be able to sample enough of the Milky Ways halo to make reasonable estimates on dark matter content one of the greatest mysteries in astronomy today!

Read more: http://www.iflscience.com/space/fast-dwarf-galaxy-generates-ripples-milky-way

Researchers Spot The Early Growth Of A Giant Galaxy, Just 3 Billion Years After The Big Bang

Researchers Spot The Early Growth Of A Giant Galaxy, Just 3 Billion Years After The Big Bang

Astronomers have spotted a giant galaxy in the earliest stages of construction some 11 billion years ago, just three billion years after the Big Bang. This mighty galaxy—named GOODS-N-774 or “Sparky”—is chucking out newborn stars at a phenomenal rate, giving scientists a rare and exciting opportunity to study a process of galaxy formation that no longer occurs in our Universe today. The study has been published in Nature.

Galaxies are massive systems of stars, dust and gas bound together by gravity. There are 3 main types of galaxies: elliptical, spiral and irregular. Elliptical galaxies, such as Sparky, are shaped like an elongated sphere. Galaxies can range considerably in size, but giant elliptical galaxies are the largest.

It was theorized that these giant, gas-deficient galaxies develop from the inside out, starting off as a large, compact core. Until now, however, these elusive cores had never been spotted because they’re unique to the early Universe and probably heavily obscured from view. According to lead author of the study Erica Nelson, these dense cores were probably able to form early on because the Universe was generally much denser in the period shortly after the Big Bang.

Sparky was identified with the help of the Hubble Space Telescope, the Spitzer Space Telescope, the Herschel Space Observatory and the W.M. Keck Observatory. While Sparky may be small, it certainly packs a punch. A mere 6,000 light-years across, it already contains around twice as many stars as our home galaxy that is some 100,000 light-years across.

Using archival far-infrared images, the researchers were also able to determine the rate of star formation in its core. Impressively, Sparky is churning out around 300 stars per year; the Milky Way produces only around ten.

The researchers postulate that this intense rate of star formation is due to the fact that the core is forming within the heart of a gravitational well crammed with dark matter, an invisible material that acts as a scaffold for galaxy formation in the early Universe. They believe a torrent of gas is pouring into this well, sparking the birth of stars.

“They’re very extreme environments,” Nelson said in a news release. “It’s like a medieval cauldron forging stars. There’s a lot of turbulence, and it’s bubbling. If you were in there, the night sky would be bright with young stars, and there would be a lot of dust, gas and remnants of exploding stars. To actually see this happening is fascinating.”

The researchers suggest that this vast amount of dust and gas is likely the reason that star-forming cores such as these have evaded astronomers before. This material would heavily obscure the region, making it difficult to spot in optical and near-infrared surveys.

“We had been searching for this galaxy for years, and it’s very exciting that we finally found it,” said co-author Pieter van Dokkum. “The big challenge is to understand the physics driving the formation of such objects.” Hopefully, he says, the James Webb Space Telescope will help us find the answer. 

Read more: http://www.iflscience.com/space/researchers-spot-early-growth-giant-galaxy-just-3-billion-years-after-big-bang

Largest-Ever Simulated Universe Created With Supercomputers

Largest-Ever Simulated Universe Created With Supercomputers

One of the principles of science is that by repeating experiments we can learn some fundamental laws of nature. This is complicated when we are trying to learn about the secrets of the universe as a whole, though, because we only have one universe. And while we can’t study multiverses, we might be able to do the next best thing.

Using supercomputers, physicists have created the largest-ever simulated universe. They created detailed catalogues of fake galaxies that can be compared with large-scale observations of real galaxies. This makes for a better understanding of the universe, as we can know the cosmological parameters with more precision.

Francisco Kitaura, lead author of the research, said in astatement: “We have developed the necessary techniques to generate thousands of simulated galaxy catalogues, reproducing the statistical properties of the observations.” The research is published inMonthly Notices of the Royal Astronomical Society.

The simulated objects were created with the intention to compare them with the real objects seen in the Baryon Oscillation Spectroscopic Survey, or BOSS, whichhas scanned a large part of the sky and precisely measured the distance of more than 1 million galaxies up to 4.5 billion light-years away.

The distribution of galaxies in the universe is not random. Galaxies and clusters of galaxies are distributed in the so-called cosmic web. The galaxies follow the filaments of the web with large voids between groups of galaxies. The formations of the web happened right after the Big Bang, with its evolution being dictated bydark matter.

Dark matter is a mysterious form of matter that only interacts gravitationally. We can see the effect of it on galaxies, but we are yet to observe it in the lab. Constraining its properties was one of the challenges in preparing this simulation. Other challenges included having a realistic distribution of galaxies and including the correct mass of the galaxies, which strongly depends on their environments.

“Now we understand better the relation between the galaxy distribution and the underlying large-scale dark matter field,”said Kitaura.”We will continue refining our methods to further understand the structures we observe in the universe.”

A 2D map of galaxydistribution. On the left is real observation, and on the right isthe simulated data.F. Kitaura

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Read more: http://www.iflscience.com/space/simulating-large-scale-universe-supercomputers

New Measurements Suggest There May Be Half As Much Dark Matter In The Milky Way As Previously Thought

New Measurements Suggest There May Be Half As Much Dark Matter In The Milky Way As Previously Thought

Using a century-old technique to probe the borders of our galaxy, a team of Australian astronomers has estimated the amount of dark matter in the Milky Way. Intriguingly, according to their new calculations, there could be half as much of this poorly understood substance in our galaxy as once thought. Their work has been published in The Astrophysical Journal.

Dark matter is an elusive substance; it doesn’t absorb, reflect or emit light, meaning it’s invisible to both our eyes and the instruments we use to detect normal matter. Because it doesn’t interact with the electromagnetic force, we only know it exists because it exerts gravitational effects on visible matter. Although we can’t see it, physicists have calculated that it makes up around 25% of the universe. The stuff of our bodies, stars, dust and planets, or “normal” matter, makes up a mere 4%. The rest is something even more strange- dark energy.

Although dark matter is very difficult to study, researchers are able to measure its mass using a method pioneered in the early 19th Century by a British astronomer called James Jeans. This technique, which was developed long before scientists even knew dark matter existed, involves measuring the speed that stars are travelling throughout our galaxy. While astronomers have been doing this for some time, they had never used it to examine the very edges of the Milky Way, which is what they did in this latest study.

By peering this far out, some 5 million billion kilometers from Earth, they were able to obtain measurements that allowed them to calculate the mass of dark matter in our galaxy. Although it was found to be a pretty huge figure, some 800,000,000,000 times the mass of our sun (8 x 1011 solar masses), this is around half of the previous estimates.

The team’s new measurement has also helped them solve a problem that has been “a thorn in the cosmological side for almost 15 years,” according to study co-author Professor Geraint Lewis.

As explained by lead author Dr. Prajwal Kafle, the widely accepted idea of galaxy formation and evolution — the Lambda Cold Dark Matter theory– predicts that there should be numerous large satellite galaxies around the Milky Way. However, when their new measurement is applied, the theory predicts that there should only be three. And that is precisely what we observe: the Large Magellanic Cloud, the Small Magellanic Cloud and the Sagittarius Dwarf Galaxy. 

[Via International Centre for Radio Astronomy Research, siliconrepublic and The Astrophysical Journal]

Read more: http://www.iflscience.com/space/new-measurements-suggest-there-may-be-half-much-dark-matter-milky-way-previously-thought

Could Dark Matter Be Made Up Of Miniscule Black Holes?

Could Dark Matter Be Made Up Of Miniscule Black Holes?

Dark matter is believed to make up about a quarter of the content of the Universe, but there actually isn’t a lot that’s known about it. It doesn’t reflect or absorb anything on the electromagnetic spectrum, making it incredibly hard to detect. Two astrophysicists from the Institute for Nuclear Research of the Russian Academy of Sciences have formulated a new hypothesis that dark matter is comprised of “black hole atoms” which are potentially either microscopic or quantum. The hypothesis was detailed in an open access format in the journal Advances in High Energy Physics.

Dark matter is unable to interact with the electromagnetic spectrum and cannot be imaged with current technology, just like black holes. However, it does interact with regular matter via gravity, just like black holes. These similarities have been observed for quite some time, leading many to think that dark matter could be composed of some form of small black hole. 

The hypothesis put forward by Vyacheslav Dokuchaev and Yury Eroshenko isn’t entirely novel, though there are some key distinctions within it. They postulate that a type of dark matter existed early in the Universe and that it had an electric charge and are essentially microscopic “black hole atoms.” As it interacted with other charged particles, it would have been left with a neutral charge that is only weakly able to interact with visible matter. Though smaller than an atom, each of these particles could have weighed from 1014 kg to 1023 kg. On the larger end of that spectrum, it would have a similar mass to the moon.

These proposed black hole atoms are similar to the friedmon particle theorized about 40 years ago that are basically the TARDIS of particle physics: it’s bigger on the inside. While the outside of this particle could be quite small, the interior could be as large as the entire Universe.

There has been some immediate skepticism of this new hypothesis from Dokuchaev and Eroshenko. Valeri Frolov, who helped co-found the friedmon theory, told Space.com that friedmons are (albeit quite subtly) able to interact with the electromagnetic spectrum. Dark matter, on the other hand, cannot. Dark matter is most likely composed of weakly interacting massive particles (WIMPs).

Despite any flaws this hypothesis has, there’s no reason to discount it quite yet. After all, nobody really knows what it is made out of. Dokuchaev and Eroshenko propose that their particle could be detected indirectly, as it would interact with visible matter and could possibly produce a flash of energy as it draws electrons into itself.

[Hat tip: Katia Moskvitch, Space.com]

Read more: http://www.iflscience.com/space/could-dark-matter-be-made-miniscule-black-holes

Scientists May Have Finally Detected A Dark Matter Signal

Scientists May Have Finally Detected A Dark Matter Signal

Could scientists have finally spotted a signal from dark matter—the elusive, theoretical substance that’s thought to make up much of the universe? After laboriously scouring through X-ray data collected from one of the European Space Agency’s telescopes, astronomers spotted a weird spike in emissions that can’t be explained by any known particle or atom, leading the team to believe that it may have come from dark matter. The work will be published next week in Physical Review Letters, but you can read a preprint version here.

Dark matter is a mysterious substance that’s eluded astronomers for decades. It can’t be directly observed because it doesn’t absorb or emit light, hence the name. Scientists have only been able to infer its existence because it seems to exert gravitational effects on normal, visible matter.

When scientists observe the speed at which galaxies are rotating, they are confronted with something strange: They are spinning so fast that they should have been ripped apart long ago because the gravity produced by observable matter is insufficient to glue them together. That’s why scientists think something invisible is giving them that extra gravity they need to remain intact. These observations have led astronomers to estimate that the dark stuff could make up as much as 80% of all matter in the universe.

While scientists have never managed to detect or measure dark matter, newly gathered observations suggest we may finally have some tangible evidence for its existence. The data came from the ESA’s XMM-Newton spacecraft, which was analyzed by an international team of researchers. After scouring through thousands of signals, they spotted a weird spike in X-ray emissions coming from two different spots in the universe: the Andromeda galaxy and the Perseus galaxy cluster. The signal doesn’t correspond to any known particle or atom, and is unlikely to be the result of a measurement or instrument error, which is why, tantalizingly, the team thinks it could have been produced by a dark matter particle.

“The signal’s distribution within the galaxy corresponds exactly to what we were expecting with dark matter, that is, concentrated and intense in the center of objects and weaker and diffuse on the edges,” study author Oleg Ruchayskiy said in a news release.

“With the goal of verifying our findings, we then looked at data from our own galaxy, the Milky Way, and made the same observations,” added co-author Alexey Boyarsky.

The researchers think that the signal could have come from the destruction of a dark matter candidate particle, possibly the hypothetical sterile neutrino. That’s because it is believed the decay of these particles, which are cousins of electron-like particles called neutrinos, could produce X-rays.

If scientists can confirm this discovery, the team believes it could spur a new era in astronomy, and may lead to the development of telescopes specially designed for studying signals coming from dark matter particles.

“We will know where to look in order to trace dark structures in space and will be able to reconstruct how the universe has formed,” added Boyarsky.

Check out this video for more info:

 

 

[Via Ecole Polytechnique Fédérale de Lausanne and Space.com]

Read more: http://www.iflscience.com/space/could-scientists-have-finally-detected-dark-matter-signal