What Is Dark Matter? Colliding Galaxy Clusters May Help Find Answer

Dark matter is a hypothetical kind of matter that cannot be seen with telescopes but accounts for most of the matter in the universe.  Dark matter is estimated to constitute 84.5% of the total matter in the universe. It has not been detected directly, making it one of the greatest mysteries in modern astrophysics.



Hubble Image of Galactic Collision 

A study of 72 large cluster collisions shows how dark matter in galaxy clusters behaves when they collide.

Image Showing How two Galaxies Collides

Astronomers have used data from NASA’s Hubble Space Telescope and the Chandra X-ray Observatory to find that dark matter interacts with itself less than previously thought. In an effort to learn more about dark matter, astronomers observed how galaxy clusters collide with each other -- an event that could hold clues about the mysterious invisible matter that makes up most of the mass of the universe.

As part of a new study, published in the journal Science on Thursday, researchers used the Hubble telescope to map the distribution of stars and dark matter after a collision. They also used the Chandra observatory to detect the X-ray emission from colliding gas clouds.

“Dark matter is an enigma we have long sought to unravel,” John Grunsfeld, assistant administrator of NASA’s Science Mission Directorate in Washington, said in a statement. “With the combined capabilities of these great observatories, both in extended mission, we are ever closer to understanding this cosmic phenomenon.”



Here are images of six different galaxy clusters taken with NASA's Hubble Space Telescope (blue) and Chandra X-ray Observatory (pink) in a study of how dark matter in clusters of galaxies behaves when the clusters collide. A total of 72 large cluster collisions were studied.  NASA and ESA

According to scientists, galaxy clusters are made of three main components -- galaxies, gas clouds and dark matter. During collisions, the gas clouds bump into each other and gradually slow down. Galaxies, on the other hand, are much less affected by this process, and because of the huge gaps between the stars within them, galaxies do not slow each other down.

“We know how gas and stars react to these cosmic crashes and where they emerge from the wreckage,” David Harvey of the École Polytechnique Fédérale de Lausanne in Switzerland, and the study’s lead author, said in the statement. “Comparing how dark matter behaves can help us to narrow down what it actually is.”

The researchers studied 72 large galaxy cluster collisions and found that, like galaxies, the dark matter continued straight through the collisions without slowing down much, meaning that dark matter do not interact with visible particles.

“There are still several viable candidates for dark matter, so the game is not over. But we are getting nearer to an answer,” Harvey said.

Source : IBT times

Compact Fusion Reactor Within A Decade, Says Lockheed Martin

American advance technology company Lockheed Martin says it’s within a decade of producing a fusion reactor that’s 90 percent smaller than previous designs.

what is fusion power ?



Fusion reactor may be the ultimate solution for today's energy crisis . Fusion is the process that powers stars. Fusion power is the energy generated by nuclear fusion processes. In fusion reactions, two light atomic nuclei fuse to form a heavier nucleus (in contrast with fission power). In doing so they release a comparatively large amount of energy arising from the binding energy due to the strong nuclear force that is manifested as an increase in temperature of the reactants. Fusion power is a primary area of research in plasma physics.

The stakes are high, and so is the enthusiasm and skepticism about Lockheed’s announcement. After all, fusion could generate much more energy much more cleanly than today’s power plants that rely on nuclear fission.

But fusion reactors are elusive. So far, no researcher has been able to wring more energy from a fusion reactor than is needed to power it up.

Most efforts to create a fusion reactor have focused on containing hot plasma, a highly ionized gas, within strong magnetic fields in what’s called a “tokamak,” a doughnut-shaped device. Some of these tokamaks already being built or tested are enormous, including the world’s largest – 30 meters tall – at an international laboratory in France known as ITER. Its projected cost is $50 billion.

In an interview with MIT Technology Review, Tom McGuire, who leads Lockheed’s fusion research, said the aerospace, defense and security company has developed a compact reactor based on what he called “magnetic mirror confinement,” which is designed to contain plasma by reflecting particles from high-density magnetic fields to low-density fields.

By “compact” Lockheed means that its research reactor measures two meters long and one meter wide, much smaller than its rivals. And according to McGuire, it’s not small for small’s sake. He argues that the reduced size makes operations and hardware revisions quicker and more efficient. “That is a much more powerful development paradigm and much less capital intensive,” he said.

Small also means that a working fusion reactor of this size might easily fit in a tractor-trailer and be taken to a remote site to generate 100 megawatts of power. He concedes, “There are no guarantees that we can get there, but that possibility is there.”

Already, Lockheed’s fusion reactor team has conducted 200 firings with plasma at its research facility in Palmdale, Calif., known as Skunk Works, but it hasn’t yet produced any data on their results. Still, McGuire said, the plasma “looks like it’s doing what it’s supposed to do.”

Astronomers may have detected the first direct evidence of dark matter

Scientists have detected a mysterious X-ray signal that could be caused by dark matter streaming out of our Sun’s core.



A sketch (not to scale) shows axions (blue) streaming out of the Sun and then converting into X-rays (orange) in the Earth's magnetic field (red). The X-rays are then detected by the XMM-Newton observatory.

Scientists in the UK may have finally found direct evidence for dark matter pouring out of our Sun.

Dark matter is an invisible mass of unknown origin, that is believed to make up 85 percent of the Universe. But despite that, scientists have never been able to directly detect it - they only know it’s there because of its gravitational effect on regular light and matter.

Now scientists at the University of Leicester have identified a signal on the X-ray spectrum which appears to be a signature of ‘axions’ - a hypothetical dark matter particle that’s never been detected before.

While we can't get too excited just yet - it will take years to confirm whether this signal really is dark matter - the discovery would completely change our understanding of how the Universe works. After all, dark matter is the force that holds our galaxies together, so learning more about it is pretty important.

The researchers first detected the signal while searching through 15 years of measurements taking by the European Space Agency’s orbiting XMM-Newton space observatory.

Unexpectedly, they noticed that the intensity of X-rays recorded by the spacecraft rose by about 10% whenever XMM-Newton was at the boundary of Earth’s magnetic field facing the Sun - even once they removed all the bright X-ray sources from the sky. Usually, that X-ray background is stable.

"The X-ray background - the sky, after the bright X-ray sources are removed - appears to be unchanged whenever you look at it," said Andy Read, from the University of Leicester, one of the lead authors on the paper, in a press release. "However, we have discovered a seasonal signal in this X-ray background, which has no conventional explanation, but is consistent with the discovery of axions."

Researchers predict that axions, if they exist, would be produced invisibly by the Sun, but would convert to X-rays as they hit Earth’s magnetic field. This X-ray signal should in theory be strongest when looking through the sunward side of the magnetic field, as this is where the Earth’s magnetic field is strongest.

And that's exactly what the scientists found.

The research has now been published in the Monthly Notices of the Royal Astronomical Society. Sadly, the first author of the paper Professor George Fraser died earlier this year.

He writes in the paper: “The direct detection of dark matter has preoccupied physics for over 30 years … It appears plausible that axions – dark matter particle candidates - are indeed produced in the core of the Sun and do indeed convert to X-rays in the magnetic field of the Earth."

The next step is for the researchers to get a larger dataset from XMM-Newton and confirm the pattern they’ve seen in X-rays. Once they’ve done that, they can begin the long process of proving that they have, in fact, detecting dark matter streaming out of our Sun’s core.

And that will take a lot of work, as physicist Christian Beck, who didn’t work on the project, told Ian Sample from The Guardian. “A true discovery of dark matter that is convincing for most scientists would require consistent results from several different experiments using different detection methods, in addition to what has been observed by the Leicester group,” said Beck.

If confirmed, it’s hard to know just how profound the impact of this discovery could be.

“These exciting discoveries, in George's final paper, could be truly ground-breaking, potentially opening a window to new physics, and could have huge implications, not only for our understanding of the true X-ray sky, but also for identifying the dark matter that dominates the mass content of the cosmos,” said Read in the press release.