• Custom Search

Dark matter ‘ghosts’ through galactic smash-ups

Dark matter ‘ghosts’ through galactic smash-ups
By Jonathan Webb
Science reporter, BBC News

Dark Matter

Space

By observing multiple collisions between huge clusters of galaxies, scientists have witnessed dark matter coasting straight through the turmoil.

Dark matter is the mysterious, invisible stuff that makes up 85% of the matter in the cosmos – and these results rule out several theoretical models put forward to explain it.

This is because it barely interacts with anything at all, including the dark matter in the oncoming galaxies.
The work appears in Science magazine.

To conduct their study, astrophysicists looked at 72 smash-ups between galactic clusters, using two space telescopes: visible light was recorded by the Hubble Space Telescope, and X-rays by the Chandra Observatory.

Scouring multiple views of the collisions, the researchers tracked the movement of the three main components of galaxies: stars, clouds of gas, and dark matter.

The violently swirling clouds of gas are hot enough to glow with X-rays, which Chandra detects. And stars can be seen in regular, visible-light images from Hubble.

Dark matter is more difficult to “see” – but not impossible. Although it does not emit or absorb light, it does have gravity, and so it bends the path of light passing nearby. This warps our view of anything on the other side of it, in an effect called “gravitational lensing”.

“Looking through dark matter is like looking through a bathroom window,” said Dr Richard Massey from Durham University, one of the study’s authors. “All the objects that you can see in the distance appear slightly distorted and warped.”

NASA

Images were used from the Hubble Space Telescope (illustrated here) and the Chandra X-Ray Observatory

Using this distortion allowed Dr Massey, with colleagues from the University of Edinburgh, University College London and Switzerland’s Ecole Polytechnique Federale de Lausanne (EPFL), to “map” the dark matter in the clusters as they collided.

‘Smash it and see’

Galaxy clusters are vast and contain huge amounts of dark matter, so when they collide – over billions of years – it offers a unique glimpse of how the stuff behaves.

“We like these collisions because it’s exactly what we’d do in the lab,” Dr Massey told BBC News.
“If you want to figure out what something is made out of, you knock it, or you throw it across the room and see where the bits go.”

In this case, the bits went straight through each other.

Unlike the gas clouds, which grind to a turbulent halt, and the stars, which mostly glide past each other, the ubiquitous dark matter passes through everything and emerges unscathed, like a ghost.
“It seems not to interact with anything at all,” Dr Massey said.

_____________________________________________________________________________

Here be ‘space dragons’

Dr Tom Kitching, UCL Mullard Space Science Laboratory

Our new measurements of the self-interaction of dark matter are some of the best yet. But statistically speaking, the strongest result from this study is in fact the confirmation that dark matter really does exist in these galaxy clusters.

We measured three things: the position of stars, the position of mass, and the position of gas. If there was no dark matter, then all of the mass that isn’t accounted for by the stars would be associated with the gas.
But we found an offset, which confirms that there is something in the clusters that is not gas, has mass, but that we cannot see: a dark matter. This detection is statistically very significant – corresponding to a probability of better than 99.99999999999% that dark matter exists in these clusters.

Sometimes I think dark matter is a terrible name. It was originally coined because the phenomenon does not emit or absorb light. But light is everywhere in the dark matter we have observed, passing within it and around it. Indeed, the lensing effect that we employed in our study uses the light from distant galaxies that has passed through dark matter.

So perhaps “transparent matter” or “clear matter” are better names. My favourite alternative is “materia incognita” (the unknown material). Maps used to be labelled “terra incognita” in areas that were unknown, and in a similar way we could be explicit about the unknown nature of this phenomenon.
However, thanks to studies like this one – and much more work planned for the coming years – our ignorance will one day end. Then we can finally give this “something” a proper name.

____________________________________________________________________________

Earlier observations of the “Bullet Cluster” – a bust-up between two particularly big groups of galaxies, now in its final stages – had already demonstrated dark matter’s weird lack of interactions, including with itself.
But this new, major survey was able to deliver much more precision, concluding that there was even less interaction than the previous work allowed for.

“If you bang your head against the wall, the electrostatic force between the molecules in your head and the ones in the wall cause a collision. This is what dark matter doesn’t seem to feel,” Dr Massey explained.
Dark matter does “feel” gravity; those interactions are the reason we know it is there, and the reason it is bound up in the galactic collisions to begin with. But the lack of almost any other interaction makes it even more mysterious than before.

Dark matter

The late-stage collision of the Bullet Cluster yielded previous observations of dark matter

“In all of these collisions that we’ve seen, it just seems to go straight through. And now we’ve seen loads more of them, we would have been able to detect any deceleration of this dark matter, if it had interacted in the ways that most theories predict,” Dr Massey said.

So although some theories remain, many can now be ruled out. This includes the idea that dark matter is some sort of “dark” version of ordinary matter, made of “dark atoms”. It must be more outlandish than that, Dr Massey said.
“Basically, we’re saying: Back to the drawing board! Let’s come up with some more ideas.”

Space has some really interesting stuff going on. Here’s a clip featuring some of the sounds of outer space.


Bright spotlight on Dawn mission to Ceres

Bright spotlight on Dawn mission to Ceres
By Jonathan Amos
BBC Science Correspondent

The bright spots inside a 92km-wide crater have been the big surprise of the encounter so far

Scientists say they are hugely excited to learn the origin of two bright spots on the surface of Ceres.

The US space agency’s Dawn probe is bearing down on the dwarf planet and on Friday will be captured by its gravity.

That will allow the satellite to spiral down in altitude in the coming months, to take ever sharper images of the spots, which sit inside a wide crater.

The striking features could be where an impact has dug out surface deposits and exposed the dwarf’s interior layers.

But deputy project scientist Dr Carol Raymond cautioned that the resolution of Dawn’s imagery was not good enough at the moment to make any definitive statements.

“These spots were extremely surprising and they have been puzzling to everyone who has seen them,” the Nasa Jet Propulsion Laboratory researcher told reporters.

“They show up in a 92km-wide crater that’s about 19 degrees North latitude. The spot in the centre is about twice as bright as the spot on the side of the crater, and as yet it has not been resolved, meaning it is smaller than the 4km pixel size [of the images].

“But its apparent brightness is already off-scale; it’s consistent with high reflective materials.”

Intriguingly, the European Space Agency’s Herschel telescope reported last year seeing water vapour coming from two sectors on Ceres. One of these sectors includes the location of the spots. That could be very significant, Dr Raymond said.

“The association with the impact crater may indicate that impact heating resulted in exposure of underlying ice [and] its vaporisation; and perhaps we’re seeing a deposit left behind which is rich in material like salts.”

Dawn will spend 14 months studying the 950km-diameter dwarf planet, which is the largest object in the asteroid belt between Mars and Jupiter.

NASA

An artist’s impression of Dawn firing its ion engine on approach to Ceres

The satellite has turned up at Ceres having previously visited the asteroid Vesta. This 530km-wide rock had the look of a punctured football, the result of a colossal collision sometime in its past that ripped a big chunk out of its southern polar region.

Ceres, on the other hand, is big enough for gravity to have pulled it into a more spherical shape.

Scientists think both bodies are fledglings that never quite made it to the planetary big time.

In the case of Vesta, it underwent a lot of the same processes that transformed the early Earth, such as differentiating its insides to include an iron core.

In contrast, Ceres’s bid to reach the major planet league probably stalled quite quickly.

Researchers believe its interior is dominated by a rocky core topped by ice that is then insulated by rocky lag deposits at the surface.

The surface of Ceres is covered with craters of many shapes and sizes

A big question the mission hopes to answer is whether there is a liquid ocean of water at depth. Some models suggest there could well be.

The evidence may well be found in Ceres’ craters which have a very muted look about them. That is, the soft interior of the dwarf has undoubtedly had the effect of relaxing their original hard outline.

“One of the prime motivations of the Dawn mission is to examine these building blocks of the planets, Vesta and Ceres, which are two intact proto-planets from the very dawn of the Solar System. They’re literally fossils that we can investigate to really understand the processes that were going on at that time,” Dr Raymond said.

At capture, the satellite will be at a separation of about 40,000km. Controllers at Earth will work in the next few weeks to reshape the orbit to get it ready for science.

One issue is that Dawn approached the dwarf from its Sun-lit side. The probe has now gone over to the dark side, and it will not come back around again to take images until late April.

But then onwards, the pictures will just get better and better as the orbit is progressively lowered.

“We’ll get to our final orbit in December of this year at just [380km] from the surface, which for context is just a little bit lower than the International Space Station orbits around the Earth. From this vantage point, Dawn will acquire its highest detail and highest resolution images of the surface,” said Nasa project manager Robert Mase.

Discovered in 1801 by the Sicilian astronomer Father Giuseppe Piazzi, Ceres is named after the Roman goddess of agriculture and harvests.

Craters on Ceres will follow a similar theme and will be named after gods and goddesses of agriculture and vegetation from mythology. Other features on the dwarf will be named after agricultural festivals.

Ceres

The soft outline of the big basin suggests that the surface has relaxed over time


Leonard Nimoy, Star Trek’s Mr Spock, dies at 83

 

 

Leonard Nimoy, Star Trek’s Mr Spock, dies at 83

Leonard Nimoy

Spock. Live Long and Prosper

US actor Leonard Nimoy, who played Mr Spock in the cult sci-fi series Star Trek, has died at the age of 83 in Los Angeles, his family has said.

His son, Adam, said he died of end-stage chronic obstructive pulmonary disease on Friday morning.

Nimoy had a long career as both an actor and director.

However he was best known for his portrayal of the half-human, half-Vulcan character in both the TV franchise and series of films.

Last year, the actor revealed he was suffering chronic lung disease COPD, despite stopping smoking 30 years ago.

It was reported earlier this week he had been taken to hospital on 19 February after suffering from chest pains.

He later tweeted: “A life is like a garden. Perfect moments can be had, but not preserved, except in memory.”

He signed off what was to be his final tweet with “LLAP” – a reference to his character’s famous catchphrase, “Live long and prosper”.

Leonard Nimoy

Spock’s Twitter

The same Twitter account was used by his granddaughter to confirm that he died at home on Friday in Bel-Air, California.

Dani Nimoy said her grandfather was an “extraordinary man, husband, grandfather, brother, actor, author – the list goes on – and friend.”

She added that special merchandise was being added to Nimoy’s website, with all proceeds going to the COPD foundation.

George Takei, who played Hikaru Sulu on Star Trek and was a friend of Nimoy’s, paid tribute to the actor.

“The word extraordinary is often overused but I think it’s really appropriate for Leonard”, Mr Takei told US broadcaster MSNBC.

“He was an extraordinarily talented man but he was also a very decent human being.”

Among the torrent of tributes on Twitter was a message from Nasa crediting Nimoy and Star Trek as an inspiration.

NASA Tweet

Thousands took to Twitter to pay tribute after Nimoy’s death was announced, including Star Trek actors past and present.

William Shatner, who as Captain Kirk acted alongside Nimoy for years in Star Trek, said he loved the actor “like a brother”.

“We will all miss his humor, his talent, and his capacity to love,” Mr Shatner said on Twitter.

Leonard Nimoy often gave Spock’s famous salute

Wil Wheaton, who played Wesley Crusher in Star Trek: The Next Generation, said: “We stood on your shoulders, and wouldn’t have had a galaxy to explore if you hadn’t been there, first. Thank you, Leonard, Rest in peace.”

More than a Vulcan
It was Nimoy’s casting as Spock in 1966 that made him in a star and, in many ways, defined his acting career.

He played the character in all three of the original series of the programme and later in several big-screen spin offs.

Nimoy had an ambivalent relationship with Spock, seeming to both cherish and resent his close association with the role.

His two volumes of autobiography – “I Am Not Spock” in 1975 and “I Am Spock” two decades later – seemed to epitomise his mixed feelings.

Leonard Nimoy 1931-2015 83 when he died
1965 appeared in rejected Star Trek pilot The Cage
1966-69 played Spock in original Star Trek series
4 Emmy award nominations, 3 for his character Spock
2013 appeared in Star Trek Into Darkness – his last film

Nimoy did have success outside of his Spock costume, in both acting and directing, and he pursued music, painting, and photography.

After the end of Star Trek’s initial run, he played master of disguise Paris in the hit adventure series Mission Impossible.

Later he directed two of the Star Trek films, The Search for Spock and The Voyage Home, and in 1987 helmed the hit comedy Three Men and a Baby, one of the highest-grossing films of that year.

Nimoy announced that he was suffering from COPD last year, writing: “I quit smoking 30 years ago. Not soon enough. Grandpa says, quit now!!”

COPD is an umbrella term for several lung diseases including chronic bronchitis, emphysema and some forms of bronchiectasis.

Sufferers experience increasing breathlessness during the advanced stages of the disease but it can be symptomless for a long time as it develops.

Shocking or intriguing NASA challenges physics to build faster than light spaceship warp drive

 

Shocking or intriguing NASA challenges physics to build faster than light spaceship warp drive

by Vandita from We Are Anonymous anahq.com

Startrek

Starship

NASA scientist Harold White has stunned the world with his announcement that he and his team has begun work on the development of a faster-than-light Warp Drive spaceship that can move faster than the speed of light defying Albert Einstein’s Theory of Special Relativity. Warp Drive, which is all set to challenge the light speed barrier, could result in speeds that could take a spacecraft to Alpha Centauri in a only two weeks even though the system is 4.3 light-years away! The idea sounds fascinating but disobeys the laws of physics.

In his 1994 paper titled The Warp Drive: Hyper-Fast Travel Within General Relativity physicist Miguel Alcubierre had suggested a mechanism by which space-time could be “warped” both in front of and behind a spacecraft. The idea immediately caught White’s attention.

“Remember, nothing locally exceeds the speed of light, but space can expand and contract at any speed. However, space-time is really stiff, so to create the expansion and contraction effect in a useful manner in order for us to reach interstellar destinations in reasonable time periods would require a lot of energy,” White told io9.

Warp Drive

Alcubierre Warp Drive

The Theory of Special Relativity does not allow objects to move faster than the speed of light within space-time. To increase the speed of moving objects to match the speed of light, it would need infinite amount of energy. White in a way suggested horrific amounts of energy —equal to the mass-energy of planet Jupiter (which is 1.9 × 1027 kilograms or 317 Earth masses). As a result, the idea was brushed aside as being far too impractical.

White later collaborated with Mark Rademaker, an artist, to create a new, more realistic design of what such a ship might actually look like. The updated model is more compact and chunkier and includes a sleek ship nestled at the center of two massive rings of negative energy which will create the warp bubble.

Mark Rademaker’s design of what such a ship might actually look like.

At the 100 Year Starship Conference in Atlanta, he said that the Warp Drive could be powered by a mass that’s even less than that of the Voyager 1 spacecraft. The reduction in mass from a Jupiter-sized planet to an object that weighs a mere 1,600 pounds completely reset White’s sense of plausibility — and NASA’s.

Warp Drive for FTL travel is at the level of speculation since NASA also considers that FTL travel is impossible. FTL results in time travel and time travel is considered far more impossible than light travel. Dr White too admits his research is still small-scale and is light years away from any type of engine that could be constructed into a spaceship like the USS Enterprise.

The story so far. Here are a number of clips from the BBC Explorations series that looks at what we have achieved so far in space travel.


Sources:

http://fossbytes.com/nasa-working-warp-drive-faster-than-light-spaceship/

http://io9.com/5963263/how-nasa-will-build-its-very-first-warp-drive

http://anonhq.com/shocking-or-intriguing-nasa-challenges-physics-to-build-faster-than-light-spaceship-warp-drive/

Alien star system buzzed the Sun

 

 

Alien star system buzzed the Sun
By Paul Rincon
Science editor, BBC News website

Scholz’s star – shown in this artist’s impression – is currently 20 light-years away. But it once came much closer

An alien star passed through our Solar System just 70,000 years ago, astronomers have discovered.

No other star is known to have approached this close to us.

An international team of researchers says it came five times closer than our current nearest neighbour – Proxima Centauri.

The object, a red dwarf known as Scholz’s star, cruised through the outer reaches of the Solar System – a region known as the Oort Cloud.

Scholz’s star was not alone; it was accompanied on its travels by an object known as a brown dwarf. These are essentially failed stars that lacked the necessary mass to get fusion going in their cores.

The findings are published in Astrophysical Journal Letters.

Observations of the dim star’s trajectory suggest that 70,000 years ago this cosmic infiltrator passed within 0.8 light years of the Sun. By comparison, Proxima Centauri is 4.2 light years away.

Close encounter
In the paper, astronomers led by Eric Mamajek at the University of Rochester, New York, say they are 98% certain that Scholz’s star travelled through what is known as the “outer Oort Cloud” – a region at the edge of the Solar System filled with trillions of comets a mile or more across.

This region is like a spherical shell around the Solar System and may extend out to as much as 100,000 Astronomical Units, or AU (one AU is the distance between the Earth and the Sun).

The Oort Cloud is thought to give rise to long-period comets that can swing past the Sun when their orbits are disturbed.

Alien

The Oort Cloud in perspective: 1 Astronomical Unit (AU) represents the distance from the Earth to the Sun

To determine the trajectory of the star, the researchers needed two pieces of information: the change in distance from the Sun to the star (its radial velocity) and the star’s motion across the sky (its tangential velocity).

Scholz’s star currently lies 20 light years away – making it a fairly nearby system. But it showed very slow tangential motion for a star this close. This indicated that it was either moving away from us or towards a future close encounter with the Solar System.

The radial velocity measurements confirmed that the binary star system was actually speeding away from us. By tracing its movements back in time, they found its close shave with the Sun occurred some 70,000 years ago.

Grand theft Oort-o?
A star passing through the Oort Cloud could potentially play gravitational havoc with the orbits of comets there, sending them on trajectories into the inner Solar System. But Dr Mamajek believes the effects of Scholz’s star on our cosmic neighbourhood were “negligible”.

“There are trillions of comets in the Oort cloud and likely some of them were perturbed by this object,” he told BBC News.

“But so far it seems unlikely that this star actually triggered a significant ‘comet shower’.”

The effect of a passing star on the Oort Cloud is a function of the star’s mass, speed and proximity. The worst case scenario for stirring up comets would be a slow-moving, massive star that came close to the Sun.

Scholz’s star came relatively close, but the binary system (the red dwarf and its brown dwarf companion) has a low mass and it was speeding by. These factors conspired to make its effect on the Oort Cloud very small.

While this is the closest flyby detected so far, Dr Mamajek thinks it’s not uncommon for alien stars to buzz the Sun. He says a star probably passes through the Oort Cloud every 100,000 years, or so.

But he suggests an approach as close – or closer – than that made by Scholz’s star is somewhat rarer. Dr Mamajek said mathematical simulations show such an event occurs on average about once every nine million years.

“So it is a bit of a strange coincidence that we happen to have caught one that passed so close within the past 100,000 years or so,” he said.


Meteorite is ‘hard drive’ from space

Meteorite is ‘hard drive’ from space

By Simon Redfern
BBC Science writer

Meteor

The Esquel meteorite consists of gem-quality crystals embedded in metal.

Researchers have decoded ancient recordings from fragments of an asteroid dating back billions of years to the start of the Solar System.

They found tiny “space magnets” in meteorites which retain a memory of the birth and death of the asteroid’s core.

Like the data recorded on the surface of a computer hard drive, the magnetic signals written in the space rock reveal how Earth’s own metallic core and magnetic field may one day die.

The work appears in Nature journal.

Using a giant X-ray microscope, called a synchrotron, the team was able to read the signals that formed more than four-and-a-half billion years ago, soon after the birth of the Solar System.

The meteorites are pieces of a parent asteroid that originally came from asteroid belt, between Mars and Jupiter.

They represents the left-over fragments of a planet that failed to form. The magnetic recording within it traps a signal of the precise moments when an iron-rich core formed in the asteroid as well as when it froze, killing its magnetic field.

The new picture of metallic core solidification in the asteroid provide clues about the magnetic field and iron-rich core of Earth.

Core values

“Ideas about how the Earth’s core evolved through [our planet’s] history are really changing at the moment,” lead researcher Dr Richard Harrison, from the University of Cambridge, told BBC News.

“We believe that Earth’s magnetic field is linked to core solidification. Earth’s solid inner core may have started to form at very interesting time in terms of the evolution of life on Earth.

“By studying an asteroid we get to see this in fast forward. We can see the start of core solidification in the magnetic records as well as its end, and start to think about how these processes work on Earth.”

Gravity

Magnetic field The Earth’s magnetic field will likely die off when the core completely freezes

The meteorites studied by the team originally fell to Earth in Argentina, and are composed of gem-quality crystals enclosed in a metallic matrix of iron and nickel.

Tiny particles, smaller than one thousandth the width of a human hair, trapped within the metal have retained the magnetic signature of the parent asteroid from its birth in the early Solar System.

“We’re taking ancient magnetic field measurements in nano-scale materials to the highest ever resolution in order to piece together the magnetic history of asteroids – it’s like a cosmic archaeological mission,” said Dr James Bryson, the paper’s lead author.

“Since asteroids are much smaller than Earth, they cooled much more quickly, so these processes occur on a shorter timescales, enabling us to study the whole process of core solidification.”

Don’t panic
Prof Wyn William, from the University of Edinburgh, who was not involved in the study, commented: “To be able to get a time stamp on these recordings, to get a cooling rate and the time of solidification, is fantastic. It’s a very nice piece of work.”

The key to the long-lived stability of the recording is the atomic-scale structure of the iron-nickel particles that grew slowly in the asteroid core and survived in the meteorites.

Scientists have attempted to synthesise the same iron-nickel structures in the lab, without widespread success so far. But their remarkable magnetic properties rival those of rare earth magnets, a key component of wind turbines and electric cars.

They may yet prove a route to making cheap, strong magnets without the need for scarce rare earth metals.

Making a final comment on the results, Dr Harrison said: “In our meteorites we’ve been able to capture both the beginning and end of core freezing, which will help us understand how these processes affected the Earth in the past and provide a possible glimpse of what might happen in the future.”

The Earth’s magnetic field will likely die off when the core completely freezes, and Earth will no longer be protected from the Sun’s radiation.

“There’s no need to panic” said Dr Harrison. “The core won’t completely freeze for billions of years, and chances are, the Sun will get us first.”


  • Custom Search