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Showing posts with label galaxy. Show all posts
Showing posts with label galaxy. Show all posts

Wednesday 22 July 2015

Dead galaxies in Coma Cluster may be packed with dark matter



New computer simulations show that these galaxies stopped star formation as early as 7 billion years ago but haven’t been ripped apart due to their dark matter.

Galaxies in a cluster roughly 300 million light-years from Earth could contain as much as 100 times more dark matter than visible matter, according to an Australian study.

The research used powerful computer simulations to study galaxies that have fallen into the Coma Cluster, one of the largest structures in the universe in which thousands of galaxies are bound together by gravity.

It found the galaxies could have fallen into the cluster as early as 7 billion years ago, which, if our current theories of galaxies evolution are correct, suggests they must have lots of dark matter protecting the visible matter from being ripped apart by the cluster.

Dark matter cannot be seen directly, but the mysterious substance is thought to make up about 84 percent of the matter in the universe.

Cameron Yozin from the University of Western Australia, who led the study, says the paper demonstrates for the first time that some galaxies that have fallen into the cluster could plausibly have as much as 100 times more dark matter than visible matter.

Yozin says the galaxies he studied in the Coma Cluster are about the same size as our Milky Way but contain only 1 percent of the stars.

He says the galaxies appear to have stopped making new stars when they first fell into the cluster between 7 and 10 billion years ago and have been dead ever since, leading astrophysicists to label them “failed” galaxies.

This end to star formation is known as “quenching.”

“Galaxies originally form when large clouds of hydrogen gas collapse and are converted to stars; if you remove that gas, the galaxy cannot grow further,” Yozin said.

“Falling into a cluster is one way in which this can happen. The immense gravitational force of the cluster pulls in the galaxy, but its gas is pushed out and essentially stolen by hot gas in the cluster itself.

“For the first time, my simulations have demonstrated that these galaxies could have been quenched by the cluster as early as 7 billion years ago.

“They have, however, avoided being ripped apart completely in this environment because they fell in with enough dark matter to protect their visible matter,” Yozin said.

Source : Astronomy Magzine

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.”

Featured Image -- 838

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

Wednesday 11 February 2015

Hubble Captures 'Happy Face' of Universe

A smiling lens

Hubble Takes a Amazing Picture which seems like Happy Face in the Space.

Of course, this is neither a miracle nor a edited picture.

The reason behind this 'Happy face' is very Complex Phenomena called Gravitational Lensing. The Eyes of the face are two Galaxies but Face's smile is due to gravity. Gravitational lensing is one of the most fascinating thing in Physics and astronomy.

This picture shows the true power of gravity. The gravity of these massive galaxies are so intense that they even distort the space-time create this amazing lens effect. The light itself distorted and gives the magnified view of galaxies.

Some astronomer believes that it is because of Dark matter, an unknown matter which is yet to be discover. These images are the strong evidence of dark matter but further research and experiments are needed to entirely prove their existence.

Hubble takes many images which shows gravitational lensing

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Saturday 31 January 2015

A NEAR-COLLISION STRETCHED THIS GALAXY LIKE A "TAFFY PULL"

Hubble image of NGC 7714 Two galaxies drifted too close together between 100 and 200 million years ago, and began to drag at and disrupt one another’s structure and shape 

At first glance,it looks like a giant rollercoaster loop.
However, this incredible image actually shows a ‘river’ of Sun-like stars that has been pulled deep into space by the gravitational tug of a bypassing galaxy
The golden loop is made of sun-like stars that have been pulled deep into space, far from the galaxy’s centre.
Experts say the galaxy, called NGC 7714, has witnessed some violent and dramatic events in its recent past.
Tell-tale signs of this brutality can be seen in NGC 7714’s strangely shaped arms, and in the smoky golden haze that stretches out from the galactic centre, they say.
The culprit is a smaller companion named NGC 7715, which lies just out of the frame of this image.
As a result, a ring and two long tails of stars have emerged from NGC 7714, creating a bridge between the two galaxies. This bridge acts as a pipeline, funnelling material from NGC 7715 towards its larger companion and feeding bursts of star formation. Most of the star-forming activity is concentrated at the bright galactic centre, although the whole galaxy is sparking new stars.
The galaxy is located approximately 100 million light-years from Earth in the direction of the constellation Pisces.
Astronomer believe that our Galaxy will also collide with its companion galaxy Andromeda after 4 billion years . Here is the Simulation of Galactic collision
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Source : Dailymail , io9

Saturday 15 November 2014

10 Wonders Of The Universe

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What's the biggest thing in the universe? Find out here, along with 9 other incredible astronomical wonders.

http://www.youtube.com/watch?v=yUbQnHvXYEI

Saturday 8 November 2014

Half of universe's stars are orphans with no galaxy

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Celestial orphans are relatively small, less massive, cooler than our sun, expert says

New observations from suborbital rocket launches and an orbiting observatory show that as many as half the stars in the universe may be orphans with no galaxy scientists said on Thursday. They found that the dim light these stars produce from the far reaches of the cosmos equals the amount coming from all the galaxies.
'The night sky on a planet around such a star would be profoundly boring and black to human eyes - no other stars, or at least very few, no Milky Way band, only distant galaxies.'                                        - Michael Zemcov, Caltech experimental astrophysicist

The phenomenon of the orphan star has been well known. Astronomers have witnessed tidal streams of stars being stripped away from colliding pairs of galaxies.




The data suggests orphan stars are probably relatively small, less massive and cooler than our Sun, but typical of most stars in the universe, said Caltech experimental astrophysicist Michael Zemcov.


The night sky as seen from Earth is brimming with starlight. But these orphans would be so distant from other stars that a view from one would offer almost complete nothingness.


"The night sky on a planet around such a star would be profoundly boring and black to human eyes - no other stars, or at least very few, no Milky Way band, only distant galaxies. You might be lucky and see your parent galaxy off in the distance like we see Andromeda," Zemcov said.


Zemcov said scientists have traced the origin of galaxies to about 13.2 billion years ago, 500 million years after the Big Bang that created the universe.


"Galaxies have been forming and interacting continuously since then, with a peak in the star formation rate about two billion years after the Big Bang," Zemcov said. "You have enough interactions over enough time, and you end up stripping out a lot of stars."




Source : cbc.ca

Wednesday 5 November 2014

Milky Way's Supermassive Black Hole Reveals Identity of Strange Object at Center of Our Galaxy

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 What are Supermassive Black Hole ?

Supermassive black hole (SMBH) is the largest type of black hole, on the order of hundreds of thousands to billions of solar masses. Most—and possibly all—galaxies are inferred to contain a supermassive black hole at their centers.In the case of the Milky Way, the SMBH is believed to correspond with the location of Sagittarius A*.

For years, astronomers have been puzzled by a bizarre object in the center of the Milky Way that was believed to be a hydrogen gas cloud headed toward our galaxy's enormous black hole. Having studied it during its closest approach to the black hole this summer, UCLA astronomers believe that they have solved the riddle of the object widely known as G2.

A team led by Andrea Ghez, professor of physics and astronomy in the UCLA College, determined that G2 is most likely a pair of binary stars that had been orbiting the black hole in tandem and merged together into an extremely large star, cloaked in gas and dust — its movements choreographed by the black hole's powerful gravitational field. The research is published today in the journal Astrophysical Journal Letters.
"We are seeing phenomena about black holes that you can't watch anywhere else in the universe," Ghez added. "We are starting to understand the physics of black holes in a way that has never been possible before."

Ghez, who studies thousands of stars in the neighborhood of the supermassive black hole, said G2 appears to be just one of an emerging class of stars near the black hole that are created because the black hole's powerful gravity drives binary stars to merge into one. She also noted that, in our galaxy, massive stars primarily come in pairs. She says the star suffered an abrasion to its outer layer but otherwise will be fine.

Astronomers had figured that if G2 had been a hydrogen cloud, it could have been torn apart by the black hole, and that the resulting celestial fireworks would have dramatically changed the state of the black hole. "G2 survived and continued happily on its orbit; a simple gas cloud would not have done that," said Ghez, who holds the Lauren B. Leichtman and Arthur E. Levine Chair in Astrophysics. "G2 was basically unaffected by the black hole. There were no fireworks."

Black holes, which form out of the collapse of matter, have such high density that nothing can escape their gravitational pull — not even light. They cannot be seen directly, but their influence on nearby stars is visible and provides a signature, said Ghez, a 2008 MacArthur Fellow.

The image below shows Sagittarius A* — the giant black hole at the center of our galaxy — appears dim in this composite image because very little material is falling into it.



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Ghez and her colleagues — who include lead author Gunther Witzel, a UCLA postdoctoral scholar, and Mark Morris and Eric Becklin, both UCLA professors of physics and astronomy — conducted the research at Hawaii's W.M. Keck Observatory, which houses the world's two largest optical and infrared telescopes.

When two stars near the black hole merge into one, the star expands for more than 1 million years before it settles back down, said Ghez, who directs the UCLA Galactic Center Group. "This may be happening more than we thought. The stars at the center of the galaxy are massive and mostly binaries. It's possible that many of the stars we've been watching and not understanding may be the end product of mergers that are calm now."

Ghez and her colleagues also determined that G2 appears to be in that inflated stage now. The body has fascinated many astronomers in recent years, particularly during the year leading up to its approach to the black hole. "It was one of the most watched events in astronomy in my career," Ghez said.

Ghez said G2 now is undergoing what she calls a "spaghetti-fication" — a common phenomenon near black holes in which large objects become elongated. At the same time, the gas at G2's surface is being heated by stars around it, creating an enormous cloud of gas and dust that has shrouded most of the massive star.

Witzel said the researchers wouldn't have been able to arrive at their conclusions without the Keck's advanced technology. "It is a result that in its precision was possible only with these incredible tools, the Keck Observatory's 10-meter telescopes," Witzel said.

The telescopes use adaptive optics, a powerful technology pioneered in part by Ghez that corrects the distorting effects of the Earth's atmosphere in real time to more clearly reveal the space around the supermassive black hole. The technique has helped Ghez and her colleagues elucidate many previously unexplained facets of the environments surrounding supermassive black holes.

The image at the top of the page is a simulation showing the possible behavior of a gas cloud that has been observed approaching the black hole at the center of the Milky Way.

Source :  daily galaxy


Monday 3 November 2014

NASA Releases Sounds From Space On SoundCloud

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NASA recently released over a half a century of sounds on SoundCloud, ranging from eerie noises from our solar system to historic moments in space exploration. The U.S. space agency recently created a SoundCloud page to reveal some of the most unusual sounds ever recorded, according to Mother Nature Network.

Although sounds in space are stifled by a vacuum, scientists have discovered ways of capturing noise using special instruments on the Voyager space probe that converts electromagnetic vibrations into sound, Gigwise reports.

The recordings include sounds of Saturn’s rings, Neptune, Jupiter, and Uranus, as well as what Earth would sound like millions of miles away. The files also contain sounds of shuttle launching and famous quotes from NASA astronauts.

Some of the sounds are quirky, chilling, and otherworldly. Here are seven of NASA’s most interesting uploads.

  1. “Earthsong” It is also called “Chorus” and is NASA’s most popular feed. The sound is produced by our own planet. It is described as an electromagnetic phenomenon caused by plasma waves in Earth’s radiation belts that hover 8,000 miles above the surface. The sound is too high for humans to hear, however ham radio operators have detected it for a long time, especially in the morning. It has been compared to the sound of birdsongs, from which the moniker is derived. NASA recorded this in 2012 with its EMFISIS probe.

  2. Saturn Radio” Saturn is home to dramatic auroras that are a lot like the northern and southern lights that dance around the Earth’s poles when solar wind hits the upper atmosphere. These lights are closely related to the planet’s strong radio emissions, first detected by the Cassini spacecraft 2002.

  3. “Interstellar Plasma” It has taken NASA’s Voyager 1 three decades since it left Earth to escape the sun’s magnetic field. This clip represents data that was recorded outside the heliosphere in 2012 and 2013. NASA calls it “The Sounds of Interstellar Space.”

  4. “Sonified Starlight” Scientists now may “sonify” non-auditory data by translating its values to noises, a lot like a Geiger counter converts silent radiation to audible clicks. Locating patterns in in data is often easier by ear, even if the data doesn’t represent sounds. The technique also helps scientists understand faraway stars, as with this clip of sonified light waves from KIC 7671081B, a variable star listed in NASA’s Kepler Input Catalog (KIC).

  5. Eerie Enceladus” This is Saturn’s sixth-largest of its several dozen moons. Enceladus spews enormous plumes of water vapor from its ice-covered surface. In 2005, the Cassini spacecraft detected a “significant atmosphere around it,” recording data from ion cyclotron waves.

  6. A Giant Leap” Neil Armstrong’s most famous words when his foot touched the surface of the moon. This was the first SoundCloud clip that NASA posted online.

  7. “Lift Off” These are the sounds of the first manned-mission to the moon, Apollo 11. The clip includes lift off, as well as the applause in the space center.





Some of NASA’s files might sound familiar to gamers.

NASA’s release of sounds from space on its SoundCloud page comprises of 63 files so far, including several of the most historic and mind-bending moments from the past 50 years of space exploration.
Source : inquisitr

Sunday 2 November 2014

Galaxies probably settled 2 billion years earlier than previously believed

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Scientists have dug deeper and discovered that galaxies actually settled in to their current forms some 2 billion years earlier than previously thought.

A group of researchers used the collective efforts of the hundreds of thousands of people that volunteered for the galaxy Zoo project to shed some light on the way that galaxies form and develop.

Dr. Brooke Simmons of the University of Oxford and her collaborators set Zoo volunteers the task of classifying the shapes of tens of thousands of galaxies observed by the Hubble Space Telescope. These objects are typically very distant, so they appeared more than 10 billion years ago, when the universe was about 3 billion years old, less than a quarter of its present age.

The newly classified galaxies were striking in that they look a lot like those in today's universe, with disks, bars and spiral arms. But theorists predict that they should have taken another 2 billion years to begin to form, so things seem to have been settling down a lot earlier than expected.

Brooke commented that they had predictions from galaxy simulations that they shouldn't find any of the barred features that we see in nearby, evolved galaxies, because very young galaxies might be too agitated for them to form. But with the public help they got in searching through many thousands of images of distant galaxies, they have discovered that some galaxies settle very early on in the universe.

The paper is published in Monthly Notices of the Royal Astronomical Society.

Source : Zee News

Thursday 30 October 2014

Evidence Builds for Dark Matter Explosions at the Milky Way’s Core

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This Fermi map of the Milky Way center shows an overabundance of gamma-rays (red indicates the greatest number) that cannot be explained by conventional sources.

So far, dark matter has evaded scientists’ best attempts to find it. Astronomers know the invisible stuff dominates our universe and tugs gravitationally on regular matter, but they do not know what it is made of. Since 2009, however, suspicious gamma--ray light radiating from the Milky Way’s core—where dark matter is thought to be especially dense—has intrigued researchers. Some wonder if the rays might have been emitted in explosions caused by colliding particles of dark matter. Now a new gamma-ray signal, in combination with those already detected, offers further evidence that this might be the case.

One possible explanation for dark matter is that it is made of theorized “weakly interacting massive particles,” or WIMPs. Every WIMP is thought to be both matter and antimatter, so when two of them meet they should annihilate on contact, as matter and antimatter do. These blasts would create gamma-ray light, which is what astronomers see in abundance at the center of our galaxy in data from the Fermi Gamma-Ray Space Telescope. The explosions could also create cosmic-ray particles—high-energy electrons and positrons (the antimatter counterparts of electrons)—which would then speed out from the heart of the Milky Way and sometimes collide with particles of starlight, giving them a boost of energy that would bump them up into the gamma-ray range. For the first time scientists have now detected light that matches predictions for this second process, called inverse Compton scattering, which should produce gamma rays that are more spread out over space and come in a different range of energies than those released directly by dark matter annihilation.

“It looks pretty clear from their work that an additional inverse Compton component of gamma rays is present,” says Dan Hooper, an astrophysicist at the Fermi National Accelerator Laboratory who was not involved in the study, but who originally pointed out that a dark matter signal might be present in the Fermi telescope data. “Such a component could come from the same dark matter that makes the primary gamma-ray signal we've been talking about all of these years.” University of California, Irvine scientists Anna Kwa and Kevork Abazajian presented the new study October 23 at the Fifth International Fermi Symposium in Nagoya, Japan and submitted their paper to Physical Review Letters.

None of the intriguing gamma-ray light is a smoking gun for dark matter. Other astrophysical processes, such as spinning stars called pulsars, can create both types of signal. “You can make models that replicate all this with astrophysics,” Abazajian says. “But the case for dark matter is the easiest, and there’s more and more evidence that keeps piling up.”

The official Fermi telescope team has long been cautious about drawing conclusions on dark matter from their data. But at last week’s symposium, the group presented its own analysis of the unexplained gamma-ray light and concluded that although multiple hypotheses fit the data, dark matter fits best. “That’s huge news because it’s the first time they’ve acknowledged that,” Abazajian says. Simona Murgia, an astrophysicist at the University of California, Irvine and a member of the Fermi collaboration’s galactic-center analysis team, presented the team’s findings. She says the complexity of the galactic center makes it difficult to know for sure how the excess of gamma rays arose and whether or not the light could come from mundane “background” sources. “It is a very interesting claim,” she says of Abazajian’s analysis. “However, detection of extended excesses in this region of the sky is complicated by our incomplete understanding of the background.”

The dark matter interpretation would look more likely if astronomers could find similar evidence of WIMP annihilation in other galaxies, such as the two dozen or so dwarf galaxies that orbit the Milky Way. “Extraordinary claims require extraordinary evidence, and I think a convincing claim of discovery would probably require a corresponding signal in another location—or by a non-astrophysical experiment—as well as the galactic center,” says Massachusetts Institute of Technology astrophysicist Tracy Slatyer, who has also studied the Fermi data from the Milky Way’s center.

Non-astrophysical experiments include the handful of so-called direct-detection experiments on Earth, which aim to catch WIMPs on the extremely rare occasions when they bump into atoms of normal matter. So far, however, none of these has found any evidence for dark matter. Instead they have steadily whittled away at the tally of possible types of WIMPs that could exist.

Other orbiting experiments, such as the Alpha Magnetic Spectrometer (AMS) on the International Space Station, which detects cosmic rays, have also failed to find convincing proof of dark matter. In fact, the AMS results seem to conflict with the most basic explanations linking dark matter to the Fermi observations. “Most people would agree that there is something rather unexpected happening at the galactic center, and it would be tremendously exciting if it turns out to be a dark matter annihilation signal,” says Christoph Weniger of the University of Amsterdam, another astrophysicist who has studied the Milky Way’s core. “But we have to confirm this interpretation by finding corroborating evidence in other independent observations first. Much more work needs to be done.”

Source : scientificamerican