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Showing posts with label physics. Show all posts
Showing posts with label physics. Show all posts

Monday 30 March 2015

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.

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Hubble Image of Galactic Collision 

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

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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.”

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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

Sunday 9 November 2014

Evidence of 'Starquakes' on Neutron Star

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An earthquake can be a pretty awe-inspiring natural event - a testament to the sheer power and size of shifting landmass. But what about seismic activity on a star? NASA's Fermi satellite recently spotted evidence of seismic waves rippling throughout a high-energy neutron star, resulting in an intense "storm" of high-energy blasts.

The star in question, called SGR J1550-5418, is a magnetar - an incredibly dense and highly magnetized neutron star that spins at an exceptionally high speed. The typical neutron star boasts a magnetic pull trillions of times stronger than the Earth's. A magnetar, by comparison, is about 1,000 times more magnetic than that.

Within the last four decades, only 23 magnetars in all have been identified, and among these stars, only three massive flares have ever been seen. The flares were related to "starquakes," in which instability of a neutron's pressing magnetic field literally shakes its surface.

"Fermi's Gamma-ray Burst Monitor (GBM) has captured the same evidence from smaller and much more frequent eruptions called bursts.

Source : nature world news

Saturday 1 November 2014

Universe may face a darker future

Artist’s impression of exocomets around Beta Pictoris

New research offers a novel insight into the nature of dark matter and dark energy and what the future of our Universe might be.

Researchers in Portsmouth and Rome have found hints that dark matter, the cosmic scaffolding on which our Universe is built, is being slowly erased, swallowed up by dark energy.

The findings appear in the journal Physical Review Letters, published by the American Physical Society. In the journal cosmologists at the Universities of Portsmouth and Rome, argue that the latest astronomical data favours a dark energy that grows as it interacts with dark matter, and this appears to be slowing the growth of structure in the cosmos.

Professor David Wands, Director of Portsmouth's Institute of Cosmology and Gravitation, is one of the research team.

He said: "This study is about the fundamental properties of space-time. On a cosmic scale, this is about our Universe and its fate.

"If the dark energy is growing and dark matter is evaporating we will end up with a big, empty, boring Universe with almost nothing in it.

"Dark matter provides a framework for structures to grow in the Universe. The galaxies we see are built on that scaffolding and what we are seeing here, in these findings, suggests that dark matter is evaporating, slowing that growth of structure."

Cosmology underwent a paradigm shift in 1998 when researchers announced that the rate at which the Universe was expanding was accelerating. The idea of a constant dark energy throughout space-time (the "cosmological constant") became the standard model of cosmology, but now the Portsmouth and Rome researchers believe they have found a better description, including energy transfer between dark energy and dark matter.

Research students Valentina Salvatelli and Najla Said from the University of Rome worked in Portsmouth with Dr Marco Bruni and Professor Wands, and with Professor Alessandro Melchiorri in Rome. They examined data from a number of astronomical surveys, including the Sloan Digital Sky Survey, and used the growth of structure revealed by these surveys to test different models of dark energy.
Professor Wands said: "Valentina and Najla spent several months here over the summer looking at the consequences of the latest observations. Much more data is available now than was available in 1998 and it appears that the standard model is no longer sufficient to describe all of the data. We think we've found a better model of dark energy.

"Since the late 1990s astronomers have been convinced that something is causing the expansion of our Universe to accelerate. The simplest explanation was that empty space – the vacuum – had an energy density that was a cosmological constant. However there is growing evidence that this simple model cannot explain the full range of astronomical data researchers now have access to; in particular the growth of cosmic structure, galaxies and clusters of galaxies, seems to be slower than expected."
Professor Dragan Huterer, of the University of Michigan, has read the research and said scientists need to take notice of the findings.

He said: "The paper does look very interesting. Any time there is a new development in the dark energy sector we need to take notice since so little is understood about it. I would not say, however, that I am surprised at the results, that they come out different than in the simplest model with no interactions. We've known for some months now that there is some problem in all data fitting perfectly to the standard simplest model."

Tuesday 28 October 2014

High-Altitude Methane Ice Cloud Discovered Floating Above Titan's Pole

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NASA scientists have uncovered a starting new find on Saturn's moon, Titan. They've found an unexpected high-altitude methane ice cloud, similar to exotic clouds formed high above Earth's own poles. This cloud in the stratosphere over Titan’s north pole (left) is similar to Earth’s polar stratospheric clouds (right). NASA scientists found that Titan’s cloud contains methane ice, which was not previously thought to form in that part of the atmosphere. Cassini first spotted the cloud in 2006. (Photo : L. NASA/JPL/U. of Ariz./LPGNantes; R. NASA/GSFC/M. Schoeberl)


NASA scientists have uncovered a starting new find on Saturn's moon, Titan. They've found an unexpected high-altitude methane ice cloud, similar to exotic clouds formed high above Earth's own poles.

The researchers first spotted the cloud with the help of NASA's Cassini spacecraft. It was part of the winter cap of condensation over Titan's north pole. Now, scientists have teased apart the data and found that the cloud contained methane ice, which produces a much denser cloud than the previously identified ethane ice.

"The idea that methane clouds could form this high on Titan is completely new," said Carrie Anderson, lead author of the new study, in a news release. "Nobody considered that possible before."

The temperatures in Titan's lower stratosphere are not the same at all latitudes. In fact, the high-altitude temperature near the north pole is far colder than just south of the equator. This temperature difference-as much as 11 degrees Fahrenheit-is enough to yield methane ice.

So how do these clouds form? The mechanisms for forming these high-altitude clouds are different from what happens in the troposphere. Titan has a global circulation pattern; warm air in the summer hemisphere wells up from the surface and enters the stratosphere, slowly making its way to the winter pole. There, the air sinks back down and cools as it descends. This forms the methane clouds.

Currently, the scientists are gathering more information about Saturn's moon in order to better understand the natural processes that occur on the alien world. This could shed light on the processes that occur on exoplanets and allow scientists to apply their findings to processes that also occur on Earth.

"Titan continues to amaze with natural processes similar to those on Earth, yet involving materials different from our familiar water," said Scott Edgington, Cassini deputy project scientist. "As we approach southern winter solstice on Titan, we will further explore how these cloud formation processes might vary with season."

Amazing picture of Supernova 1987A

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Real image SN 1987A located at 1,68,000 light years from earth in Large Magellanic Cloud (Another Galaxy)

you can imagine the power of this supernova by understanding that even it was located at another galaxy it was visible to the naked eye. It was the first supernova that modern astronomers had to observe a SN and to use modern technology in that observation allowing them to gather much more data.

Supernovae are extremwely rare events. About 1 every 200 years is visible and they only last for a month or two.

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image of SN 1987A

Sunday 26 October 2014

Compact Fusion Reactor Within A Decade, Says Lockheed Martin

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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 ?

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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.”