08-10-11

Does dark energy accelerate space missions ? ESA has a plan to launch Euclid mission to find more about dark energy.

 

 

October 05, 2011

 

dark energy, ESA, cosmology,

The movie stills pictured above illustrate the formation of clusters and large-scale filaments in the Cold Dark Matter model with dark energy.

 

copyright :

 

http://upload.wikimedia.org/wikipedia/commons/thumb/7/7d/...

 

wikimedia commons

 

Perfect timing: Yesterday, three astronomers received the news every scientist wants: they would be receiving the physics Nobel Prize for their work in discovering dark energy, a repulsive force that is ramping up the expansion of the universe.

 

So it was somehow fitting that, on the very same day, European Space Agency officials were approving a space mission, called Euclid, that would pin down more precisely dark energy’s key parameters.

 

“It was just coincidence, really,” says David Schlegel, principal investigator for BOSS, a ground-based mission that is also trying to get a handle on the stuff that looks a lot like a cosmological constant, the fudge factor that Einstein introduced in his relativity equations when he thought the universe was static, but later regretted.

 

Okay, so the prize has nothing to do with ESA’s decision.

 

But will it bolster the case for other dark energy missions?

 

In the United States, NASA, the Energy Department and the National Science Foundation are all trying to get a piece of the action. NASA’s WFIRST is the most expensive mission and the most sought after (it was ranked tops in the US decadal survey), and it’s probably the most capable.

 

 

But it’s stuck in line behind the James Webb Space Telescope, and so most observers think it doesn’t have a chance of flying at all until the 2020s.

 

The selection of Euclid, a very similar mission that would scoop much of the early science, may put further pressure on NASA to attempt what has failed in the past: a mission merger.

 

 

Ground-based dark energy experiments may get a lot more bang for the buck -- but even there, money is a problem.

 

 

LSST, another community favorite that will make major strides in measuring dark energy, still needs cash.

 

 

In a universe that keeps moving faster and faster, missions like LSST and WFIRST seem to get farther and farther away.

 

“It seems like it’s so far in the future,” says Schlegel.

 

copyright :

 

http://blogs.nature.com/news/2011/10/post_85.htm

l

 

26-06-11

Multiverse From Wikipedia, the free encyclopedia

cosmology,multiverse,

copyright :

http://commons.wikimedia.org/wiki/File:Multiverse.jpg

 

The multiverse (or meta-universe, metaverse) is the hypothetical set of multiple possible universes (including the historical universe we consistently experience) that together comprise everything that exists: the entirety of space, time, matter, and energy as well as the physical laws and constants that describe them.


The term was coined in 1895 by the American philosopher and psychologist William James.


The various universes within the multiverse are sometimes called parallel universes.


The structure of the multiverse, the nature of each universe within it and the relationship between the various constituent universes, depend on the specific multiverse hypothesis considered.


Multiverses have been hypothesized in cosmology, physics, astronomy, religion, philosophy, transpersonal psychology and fiction, particularly in science fiction and fantasy.


In these contexts, parallel universes are also called "alternative universes", "quantum universes", "interpenetrating dimensions", "parallel dimensions", "parallel worlds", "alternative realities", "alternative timelines", and "dimensional planes," among others.

 

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http://en.wikipedia.org/wiki/Multiverse

 

20-06-11

Observation of Rare Particles May Shed Light On Why the Universe Has More Matter Than Antimatter

 

cosmology, antimatter,cern

copyright :


http://commons.wikimedia.org/wiki/File:3D_image_of_Antihy...


ScienceDaily (June 19, 2011) — Shortly after experiments on the Large Hadron Collider (LHC) at the CERN laboratory near Geneva, Switzerland began yielding scientific data last fall, a group of scientists led by a Syracuse University physicist became the first to observe the decays of a rare particle that was present right after the Big Bang.

 

 

By studying this particle, scientists hope to solve the mystery of why the universe evolved with more matter than antimatter.


copyright :

 

http://www.sciencedaily.com/releases/2011/03/110328101306...

 

20-04-11

Antigravity Could Replace Dark Energy as Cause of Universe’s Expansion

 

 

anti-gravity,dark energy,cosmology

copyright :


http://commons.wikimedia.org/wiki/File:NGC_3021_Hubble.jp...

 

Since the late 20th century, astronomers have been aware of data that suggest the universe is not only expanding, but expanding at an accelerating rate.

 

According to the currently accepted model, this accelerated expansion is due to dark energy, a mysterious repulsive force that makes up about 73% of the energy density of the universe.

 

Now, a new study reveals an alternative theory: that the expansion of the universe is actually due to the relationship between matter and antimatter.

 

According to this study, matter and antimatter gravitationally repel each other and create a kind of “antigravity” that could do away with the need for dark energy in the universe.

 

copyright :


http://www.universetoday.com/84934/antigravity-could-repl...

 

17-03-11

NASA Prepares Antimatter-Hunting Detector for Space Shuttle Launch

 

16 March 2011

 

 

cosmologyn,dark matter,AMS,Space Shuttle,ISS

copyright image :

http://commons.wikimedia.org/wiki/File:AMS-01.jpg?uselang...

 

 

A high-tech astrophysics experiment that will probe the mysteries of our universe is getting ready to fly to the International Space Station aboard the space shuttle Endeavour when it launches on its final mission next month.


The Alpha Magnetic Spectrometer (AMS) is a particle physics detector that will primarily measure high-energy particles in space, called cosmic rays, and search for signs of antimatter and mysterious dark matter in the universe.

 

copyright :


http://www.space.com/11149-nasa-antimatter-detector-shutt...

26-02-11

Dark Matter: New Evidence on How Galaxies Are Born

 

By Michael D. Lemonick Wednesday, Feb. 23, 2011

 

dark matter,halo,cosmology

Copyright : http://commons.wikimedia.org/wiki/File:Hs-2007-17-a-full_...

 

If you think it's hard to swallow the concept of dark matter, you're not alone.

 

Decades ago, a few astronomers began to suspect that the universe was swarming with some mysterious, invisible substance that was yanking galaxies around with its own powerful gravity.

 

And for those same decades, most of those astronomers' colleagues dismissed the notion as pretty much nuts.

 

But the evidence kept mounting, and nowadays dark matter is a firmly established concept in modern astrophysics.

 

It pretty much has to exist, in fact, to explain why individual galaxies spin as fast as they do without flying apart, and why groups of galaxies move the way they do in relation to one another.

 

If there weren't 10 times as much dark matter as there are stars and gas clouds and other visible matter, the universe would make no sense.

 

Nature abhors irrationality, and so we live in a universe in which just about every galaxy, including the Milky Way, is held safely inside a huge blob of dark matter like a butterfly floating inside a glass paperweight.

 


Copyright and Read more

 

http://www.time.com/time/health/article/0,8599,2052614,00...

 

 

 

18-02-11

Dark energy is not directly detectable, but scientists can track its footsteps through history.

 

dark matter,the hunt,cosmology

 

copyright

http://upload.wikimedia.org/wikipedia/commons/c/c9/Dark_m...

 

A massive survey of distant galaxies should help unravel a mind-bending cosmic mystery: Why has the expansion of the universe sped up ?


copyright

http://news.discovery.com/space/dark-energy-galaxies-univ...

 

 

17-02-11

Herschel finds less dark matter but more stars

 

dark matter,Herschel

copyright

http://upload.wikimedia.org/wikipedia/commons/9/9d/Struct...


16 February 2011

 

ESA’s Herschel space observatory has discovered a population of dust-enshrouded galaxies that do not need as much dark matter as previously thought to collect gas and burst into star formation.

 

copyright

http://www.esa.int/esaCP/SEMRQ3PT1KG_index_0.html

 

 

28-01-11

Hunt for dark matter closes in at Large Hadron Collider

 

Wednesday 26 January 2011


Physicists are closer than ever to finding the source of the Universe's mysterious dark matter, following a better than expected year of research at the Compact Muon Solenoid (CMS) particle detector, part of the Large Hadron Collider (LHC) at CERN in Geneva.

 

cern,lhc,cms,dark matter

 


copyright

http://commons.wikimedia.org/wiki/File:LHC,_CERN.jpg?usel...

Max Braun on Flickr

 

 

The scientists have now carried out the first full run of experiments that smash protons together at almost the speed of light.

 

When these sub-atomic particles collide at the heart of the CMS detector, the resultant energies and densities are similar to those that were present in the first instants of the Universe, immediately after the Big Bang some 13.7 billion years ago.

 

The unique conditions created by these collisions can lead to the production of new particles that would have existed in those early instants and have since disappeared.

 

The researchers say they are well on their way to being able to either confirm or rule out one of the primary theories that could solve many of the outstanding questions of particle physics, known as Supersymmetry (SUSY).

 

Many hope it could be a valid extension for the Standard Model of particle physics, which describes the interactions of known subatomic particles with astonishing precision but fails to incorporate general relativity, dark matter and dark energy.

 

Dark matter is an invisible substance that we cannot detect directly but whose presence is inferred from the rotation of galaxies.

 

Physicists believe that it makes up about a quarter of the mass of the Universe whilst the ordinary and visible matter only makes up about 5% of the mass of the Universe.

 

Its composition is a mystery, leading to intriguing possibilities of hitherto undiscovered physics.

 

Professor Geoff Hall from the Department of Physics at Imperial College London, who works on the CMS experiment, said:

"We have made an important step forward in the hunt for dark matter, although no discovery has yet been made.

 

These results have come faster than we expected because the LHC and CMS ran better last year than we dared hope and we are now very optimistic about the prospects of pinning down Supersymmetry in the next few years."

 


copyright :

 

http://www3.imperial.ac.uk/newsandeventspggrp/imperialcol...

 

 

 

16-01-11

Dark-Matter Galaxy Detected: Hidden Dwarf Lurks Nearby?

 

Richard A. Lovett in Seattle, Washington


for National Geographic News


Published January 14, 2011

 

Milky Way.jpg

 

Copyright :

http://upload.wikimedia.org/wikipedia/commons/f/fd/Our_Mi...

 

An entire galaxy may be lurking, unseen, just outside our own, scientists announced Thursday.

 


The invisibility of "Galaxy X"—as the purported body has been dubbed—may be due less to its apparent status as a dwarf galaxy than to its murky location and its overwhelming amount of dark matter, astronomer Sukanya Chakrabarti speculates.

 

Detectable only by the effects of its gravitational pull, dark matter is an invisible material that scientists think makes up more than 80 percent of the mass in the universe.

 

Chakrabarti, of the University of California, Berkeley, devised a technique similar to that used 160 years ago to predict the existence of Neptune, which was given away by the wobbles its gravity induced in Uranus's orbit.

 

Based on gravitational perturbations of gases on the fringes of our Milky Way galaxy, Chakrabarti came to her conclusion that there's a unknown dwarf galaxy about 260,000 light-years away.


With an estimated mass equal to only one percent the mass of the Milky Way, Galaxy X is still the third largest of the Milky Way's satellite galaxies, Chakrabarti predicts.


The two Magellanic are each about ten times larger.


If it exists, Galaxy X isn't likely to be composed entirely of dark matter.


It should also have a sprinkling of dim stars, Chakrabarti said.


"These should provide enough light for astronomers to see it, now that they know where to look," she said.


The reason the dark matter galaxy hasn't yet been seen, she added, is because it lies in the same plane as the Milky Way disc.


Clouds of gas and dust stand between us and Galaxy X, confounding telescopes.

 

 

 

Copyright : http://news.nationalgeographic.com/news/2011/01/110114-ga...

 

14-01-11

Harvard-Smithsonian Center For Astrophysics - Better Measuring Dark Energy

 

 

Press Release

Release No.: 2011-04

For Release: Thursday, January 13, 2011 09:00:00 AM EST

 

Dark Energy.jpg

 

Copyright : http://commons.wikimedia.org/wiki/File:Cosmological_compo...

 


The Best Way to Measure Dark Energy Just Got Better

 

Seattle, WA

 

Dark energy is a mysterious force that pervades all space, acting as a "push" to accelerate the Universe's expansion.

 

Despite being 70 percent of the Universe, dark energy was only discovered in 1998 by two teams observing Type Ia supernovae.

 

A Type 1a supernova is a cataclysmic explosion of a white dwarf star.

 

These supernovae are currently the best way to measure dark energy because they are visible across intergalactic space.

 

Also, they can function as "standard candles" in distant galaxies since the intrinsic brightness is known.

 

Just as drivers estimate the distance to oncoming cars at night from the brightness of their headlights, measuring the apparent brightness of a supernova yields its distance (fainter is farther).

 

Measuring distances tracks the effect of dark energy on the expansion of the Universe.

 

The best way of measuring dark energy just got better, thanks to a new study of Type Ia supernovae led by Ryan Foley of the Harvard-Smithsonian Center for Astrophysics. 

 

He has found a way to correct for small variations in the appearance of these supernovae, so that they become even better standard candles.

 

The key is to sort the supernovae based on their color.

 

"Dark energy is the biggest mystery in physics and astronomy today.

 

Now, we have a better way to tackle it," said Foley, who is a Clay Fellow at the Center.

 

He presented his findings in a press conference at the 217th meeting of the American Astronomical Society.

 

The new tool also will help astronomers to firm up the cosmic distance scale by providing more accurate distances to faraway galaxies.

 

Type Ia supernovae are used as standard candles, meaning they have a known intrinsic brightness.

 

However, they're not all equally bright.

 

Astronomers have to correct for certain variations.

 

In particular, there is a known correlation between how quickly the supernova brightens and dims (its light curve) and the intrinsic peak brightness.

 

Even when astronomers correct for this effect, their measurements still show some scatter, which leads to inaccuracies when calculating distances and therefore the effects of dark energy.

 

Studies looking for ways to make more accurate corrections have had limited success until now.

 

"We've been looking for this sort of 'second-order effect' for nearly two decades," said Foley.

 

Foley discovered that after correcting for how quickly Type Ia supernovae faded,

they show a distinct relationship between the speed of their ejected material and their color: the faster ones are slightly redder and the slower ones are bluer.

 

Previously, astronomers assumed that redder explosions only appeared that way because of intervening dust, which would also dim the explosion and make it appear farther than it was.

 

Trying to correct for this, they would incorrectly calculate that the explosion was closer than it appeared.

 

Foley's work shows that some of the color difference is intrinsic to the supernova itself.

 

The new study succeeded for two reasons.

 

First, it used a large sample of more than 100 supernovae.

 

More importantly, it went back to "first principles" and reexamined the assumption that Type Ia supernovae are one average color.

 

The discovery provides a better physical understanding of Type Ia supernovae and their intrinsic differences.

 

It also will allow cosmologists to improve their data analysis and make better measurements of dark energy - an important step on the road to learning what this mysterious force truly is, and what it means for the future of the cosmos.

 

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

 


Copyright : http://www.cfa.harvard.edu/news/2011/pr201104.html

 

17-12-10

Physicists propose mechanism that explains the origins of both dark matter and 'normal' matter

 

December 10, 2010 by Lisa Zyga Enlarge

 

Defining_Dark_Matter_and_Energy_in_a_4th_Etheric_System.png

 

WIKIMEDIA COMMONS IMAGE

 

(PhysOrg.com) -- Through precise cosmological measurements, scientists know that about 4.6% of the energy of the Universe is made of baryonic matter (normal atoms), about 23% is made of dark matter, and the remaining 72% or so is dark energy.

 

Scientists also know that almost all the baryonic matter in the observable Universe is matter (with a positive baryon charge) rather than antimatter (with a negative baryon charge).

 

But exactly why this matter and energy came to be this way is still an open question.

 

In a recent study, physicists have proposed a new mechanism that can generate both the baryon asymmetry and the dark matter density of the Universe simultaneously.

 

 


copyright - credits :


http://www.physorg.com/news/2010-12-physicists-mechanism-...

 

14-12-10

No evidence of time before Big Bang.

Published online 10 December 2010 | Nature | doi:10.1038/news.2010.665

 

Latest research deflates the idea that the Universe cycles for eternity.

 

Edwin Cartlidge


Circular ripples in the cosmic microwave background have been making waves with theoreticians.

 

NASA

Our view of the early Universe may be full of mysterious circles — and even triangles — but that doesn't mean we're seeing evidence of events that took place before the Big Bang.

 

So says a trio of papers taking aim at a recent claim that concentric rings of uniform temperature within the cosmic microwave background — the radiation left over from the Big Bang — might, in fact, be the signatures of black holes colliding in a previous cosmic 'aeon' that existed before our Universe.

 

Dark_matter_halo.png

Dark Matter Halo

WIKIMEDIA COMMONS

 


copyright - credits : http://www.nature.com/news/2010/101210/full/news.2010.665...

26-11-10

Mini-oerknak resulteert in superhete vloeistof (LHC - CERN)

25 november 2010


allesoversterrenkunde.nl
 

 

IMAGE.jpg

 

copyright - credits


http://www.scienceparkamsterdam.nl/onderzoek/nieuwsberich...

 

Kort na de oerknal was het heelal een extreem dikke, superhete vloeistof.

 

Dat is de verrassende ontdekking die onderzoekers hebben gedaan met de Large Hadron Collider (LHC), de grote deeltjesversneller in Zwitserland.


Op 7 november begonnen wetenschappers een nieuw experiment met de LHC, waarbij zij de kernen van loodatomen met enorme snelheden tegen elkaar lieten botsen.


Bij die botsingen ontstonden kleine vuurballen van subatomaire deeltjes met een temperatuur van meer dan 10 biljoen graden.
 

Het idee achter dit experiment was om de 'oersoep' van deeltjes te reproduceren, het zogeheten quark-gluonenplasma, zoals die een miljoenste seconde na het
ontstaan van het heelal moet hebben bestaan.


Quarks en gluonen zijn de bouwstenen van de neutronen en protonen die de atomen vormen.


Volgens veel modellen die de deeltjesstroom van dit subatomaire vuurwerk beschrijven, zou deze oersoep zich als een gas moeten gedragen.


Maar uit de waarnemingen blijkt nu dat de oersoep, precies zoals de naam al aangeeft, meer weg had van een vloeistof.


Ook de dichtheid van de subatomaire deeltjes die bij de botsingen vrijkwamen, verrast de onderzoekers: bij de 'mini-oerknallen' werden veel meer van die
deeltjes gevormd dan verwacht.


Het is volgende wetenschappers overigens nog te vroeg om uit deze eerste resultaten verregaande conclusies te trekken over de structuur van het jonge heelal.

 

© Eddy Echternach

www.astronieuws.nl

 

copyright-credits

http://allesoversterrenkunde.nl/nieuws/4274-Mini-oerknak-...

 

 

22-11-10

Penrose: WMAP Shows Evidence of ‘Activity’ Before Big Bang

22nd November 2010


Have scientists seen evidence of time before the Big Bang, and perhaps a verification of the idea of the cyclical universe?


One of the great physicists of our time, Roger Penrose from the University of Oxford, has published a new paper saying that the circular patterns seen in the WMAP mission data on the Cosmic Microwave Background suggest that space and time perhaps did not originate at the Big Bang but that our universe continually cycles through a series of “aeons,” and we have an eternal, cyclical cosmos.


His paper also refutes the idea of inflation, a widely accepted theory of a period of very rapid expansion immediately following the Big Bang.

 

Sir Roger Penrose.jpg

 

Copyright - Credits : Universe Today

 

http://www.universetoday.com/79750/penrose-wmap-shows-evi... 

 

12-11-10

Hubble Provides Most Detailed Dark Matter Map Yet

 

11th November 2010

 

DarkMatterAbell.jpg

 

Nasa Hubble Space Telescope shows the distribution of dark matter in the center of the giant galaxy cluster Abell 1689. (more than 1000 galaxies with trillions of stars).

 

Credit: NASA, ESA, D. Coe (NASA Jet Propulsion Laboratory/California Institute of Technology,
and Space Telescope Science Institute), N. Benitez (Institute of Astrophysics of Andalusia, Spain), T. Broadhurst (University of the Basque Country, Spain), and H. Ford (Johns Hopkins University).

 

Credits :

 

http://www.universetoday.com/78309/hubble-provides-most-d...

 

25-09-10

Doorbraak of gelul in de ruimte ?

 

25 september 2010


de Volkskrant 
 

De Amerikaanse natuurkundige Greg Landsberg zegt een nieuwe theorie over verdwijnende ruimtelijke dimensies te hebben gevonden die het antwoord zou kunnen verschaffen op allerlei netelige vragen.

 

Nederlandse collega's regeren geërgerd. 'Toe maar, dit kan er ook wel bij.'


‘Een nieuw paradigma’ noemt hij het zelf. Speculatief, jazeker, maar daarom niet minder veelbelovend.

 

Greg Landsberg, natuurkundige aan de Amerikaanse Brown University, raakt er niet over uitgepraat.

 

Samen met vier collega’s leurt hij sinds een paar maanden met het idee dat het aantal ruimtelijke dimensies in het heelal afhankelijk is van de schaal waarop je de dingen bekijkt.

 

‘Misschien levert dit een oplossing voor allerlei netelige kwesties in de deeltjesfysica en de kosmologie,’ ratelt hij over de telefoon vanuit deeltjeslaboratorium CERN in Genève. ‘En wie weet lossen we het raadsel van de tijd er ook wel mee op.’

 

Netelige kwesties zijn er volop in de moderne natuurwetenschap. Waarom zijn er bijvoorbeeld drie deeltjesfamilies in plaats van één?

 

Wat is zwaartekracht? Waarom is er meer gewone materie dan antimaterie in het heelal? Hoe komt het dat het heelal steeds sneller uitdijt?

 

Waaruit bestaat de mysterieuze donkere materie? Valt de relativiteitstheorie ooit te rijmen met de quantumfysica?

 

En, inderdaad, wat is tijd eigenlijk? Wie het allemaal weet, mag het zeggen.

 

En wie het niet weet, hoeft kennelijk ook zijn mond niet te houden.

 

De meest uiteenlopende modellen, theorieën, concepten en luchtballonnetjes vinden de laatste jaren hun weg naar wetenschappelijke blogs, preprint servers, of zelfs naar de pagina’s van Physical Review Letters. Een vijfde kracht, schaduwmaterie, asymmetrische branen – het komt allemaal voorbij.

Dimensies.jpg

De onbewijsbare snaartheorie met zijn 10^500 heelallen, stevig gepromoot door niemand minder dan Stephen Hawking, is eigenlijk nog een van de serieuzere ideeën.

 

Van de ‘verdwijnende dimensies’ van Landsberg en zijn collega’s kijkt een theoretisch fysicus nauwelijks meer op.

 

‘Buitengewoon onaangenaam’ vindt kosmoloog Vincent Icke van de Leidse Sterrewacht deze wildgroei aan ‘loze speculaties’.

 

‘Ik sta positief tegenover dwarse denkers,’ zegt hij, ‘maar je moet wel met een verdomd goed onderbouwd idee komen, wil ik het serieus nemen.

 

Nu nemen mensen onbeperkt de vrijheid om maar te zeggen wat ze blieven.

 

Neem dat snaargelul, daar is al dertig jaar niets uitgekomen dan gebakken lucht en af en toe een wiskundeprijsje.

 

Ik vind dat laf.’ Theoretisch natuurkundige Gerard ’t Hooft van de Universiteit Utrecht, op werkbezoek in Turkije, is het met Icke eens.

 

‘Men schrijft er maar op los,’ mailt de Nobelprijswinnaar. ‘Verdwijnende dimensies, toe maar, het kan er ook wel bij.’

9_Dimensions.jpg

 

Landsberg – in 1967 in Moskou geboren – ziet dat natuurlijk heel anders. Er zijn inderdaad meer theorieën dan theoretici, grapt hij met een licht Russisch accent, maar nieuwe ideeën die misschien bevestigd zouden kunnen worden door toekomstige experimenten, kun je niet zomaar negeren.

 

Afgelopen zomer, tijdens de International Conference on High-Energy Physics in Parijs, was er weliswaar veel kritiek op het ‘nieuwe paradigma’, maar toch vooral veel belangstelling. Geen wonder, aldus Landsberg, want wie weet komt de nieuwe deeltjesversneller van CERN nog dit jaar met ondersteunende resultaten.

 

Dun rietje

 

Begin vorige eeuw speculeerden Theodor Kaluza en Oskar Klein al over extra dimensies, in een vruchteloze poging om zwaartekracht en elektromagnetisme in één beschrijving te verenigen.

 

Volgens de Kaluza-Kleintheorie bestaat er naast lengte, breedte en hoogte een vierde ruimtelijke dimensie.

 

Die zou echter niet oneindig uitgestrekt zijn, maar heel compact, waardoor je er alleen op miscroscopische schaal mee te maken krijgt.

 

Alsof je een eendimensionale lijn ziet, die bij nadere beschouwing een tweedimensionaal oppervlak blijkt te zijn, heel strak opgerold tot een extreem dun rietje.

 

‘In ons model is er echter geen sprake van extra dimensies, maar van ‘verdwijnende’ dimensies,’ zegt Landsberg.

 

Hoe nauwkeuriger je kijkt, hoe minder ruimtelijke dimensies er zijn.

 

Precies andersom dus dan bij Kaluza en Klein. Op een natuurkundeworkshop in Heidelberg, vorig jaar zomer, begon het balletje te rollen.

 

‘Tijdens een etentje met twee andere natuurkundigen en twee kosmologen bleek dat die vanishing dimensions wel eens een verklaring zouden kunnen vormen voor een aantal problemen in de moderne natuurwetenschap.’

 

Om uit te leggen hoe het werkt, vergelijkt Landsberg de ruimte met een opgefrommeld vloerkleed.

 

Dat is een driedimensionale structuur, maar als je beter kijkt zie je dat het om een tweedimensionaal kleed gaat, en pak je er een loep bij, dan blijkt het hele kleed geweven te zijn van één enkele eendimensionale draad.

 

‘Op de allergrootste schaal, vergelijkbaar met de afmetingen van het waarneembare heelal, zou onze driedimensionale ruimte ook weer geplooid en gevouwen kunnen zijn tot een vierdimensionaal geheel,’ aldus Landsberg.

 

Of er op nóg grotere schaal zelfs sprake kan zijn van een vijfde dimensie, durft hij niet te zeggen. ‘Alles is mogelijk.’

 

Maar daar zit ’m nou net de kneep, volgens de criticasters – alles lijkt maar te kunnen.

‘Ik neem een exotisch idee alleen serieus als er meetbare consequenties uit tevoorschijn komen,’ zegt Icke, ‘of als er fundamentele problemen mee verklaard worden.

 

Veel andere dingen dragen weinig of niets bij, of kunnen zelfs nooit door waarnemingen en experimenten worden onderbouwd of weerlegd.

 

Dan is zo’n theorie volslagen gratuit.’ Ook snaar-theoreticus Robbert Dijkgraaf van de Universiteit van Amsterdam is bepaald niet onder de indruk: ‘Het theoretische en experimentele laagje ijs waarop Landsberg en zijn collega’s schaatsen is erg dun.’

 

’t Hooft is bij nader inzien toch net iets milder. ‘Deze mensen weten in ieder geval waar ze over praten, en zien dus zelf de moeilijkheden ook wel in,’ zegt hij.

 

‘Maar ik vind de prijs die je betaalt voor deze theorie nogal hoog: allerlei waardevolle concepten lijken te sneuvelen, en er komt weinig bruikbaars voor in de plaats.’

 

Bovendien, aldus ’t Hooft, moet alles wel ‘streng logisch in elkaar zitten, en dat heb ik nog niet gezien.’ Overigens werkt hij zelf ook aan een ‘wild idee’ dat conforme gravitatie heet. ‘Maar dat is verre van uitgewerkt en nog niet wetenschappelijk onderbouwd.’

 

Landsberg blijft voorlopig onverminderd enthousiast. Als de driedimensionale ruimte op de grootste schaal gevouwen en geplooid is, kan een ander deel van het heelal zich vlak bij het onze bevinden, op zeer kleine afstand in de vierde dimensie.

 

Tussen die ‘naburige’ delen kunnen dan quantumeffecten optreden die een beetje vergelijkbaar zijn met het beroemde Casimir-effect.

 

Dat zou mogelijk een verklaring kunnen opleveren voor de onbegrepen donkere energie, die tot de versnellende uitdijing van het heelal leidt. ‘Maar daar moeten inderdaad nog realistische wiskundige modellen voor worden uitgewerkt,’ geeft hij toe.

 

Botsingsexperimenten

 

En wat als er op microscopische schaal inderdaad dimensies verdwijnen?

 

‘Dan gaan we dat misschien zien in botsingsexperimenten in de LHC-versneller van CERN,’ zegt Landsberg, die zelf aan een van de CERN-experimenten meewerkt.

 

‘Je verwacht dan dat de deeltjes die bij een extreem energierijke botsing geproduceerd worden voornamelijk in één vlak bewegen.

 

Voorzichtige aanwijzingen daarvoor blijken een jaar of tien geleden al eens te zijn waargenomen, maar die resultaten brachten het toen niet verder dan een vrij obscuur Russisch tijdschrift, waardoor ze nooit veel aandacht hebben gekregen.’

 

‘Natuurlijk kun je theoretici niet verbieden met vergezochte ideeën te komen,’ zegt Vincent Icke.

‘Het verbieden van een theorie komt altijd van waarnemingen en experimenten. De natuur zal wel uitmaken wat mag en wat niet.’

 

Maar, verzucht hij, als de LHC-metingen niets te zien geven, kunnen Landsberg en zijn collega’s zich altijd verschuilen achter de conclusie dat de effecten dan misschien pas bij een nóg veel hogere energie optreden.

 

‘In het Engels heet dat weaseling out. Dat vind ik het glibberige eraan. Ik houd meer van mouwen opstropen en rekenen.

 

Houd je eerst maar eens bezig met de dingen die wél meetbaar zijn.’

 

Robbert Dijkgraaf ziet veel meer in de snaartheorie als route naar een oplossing voor de crisis in de deeltjesfysica en de kosmologie.

 

‘Op kleine lengteschalen vervagen onze klassieke ideeën over ruimte en dimensie misschien wel, en moeten ze worden vervangen door quantumbegrippen,’ zegt hij.

 

Maar Gerard ’t Hooft loopt ook daar niet warm voor: ‘Stephen Hawking moet zelf weten waar hij zijn geld op zet, maar de snaartheorie komt vaak ook met flutverklaringen.’

 

Zo lang er nog zo veel onenigheid is over de betekenis van een ‘gevestigd’ idee als de snaartheorie, kun je het creatieve natuurkundigen als Greg Landsberg misschien niet kwalijk nemen dat ze plezier beleven aan het speculeren over verdwijnende dimensies.

 

'Misschien was er héél kort na de geboorte van het heelal wel sprake van slechts één ruimtelijke dimensie en één tijddimensie,’ filosofeert hij er dan ook vrolijk op los. ‘Wie weet komen we er op deze manier ooit nog eens achter waarom je in de ruimte wél alle kanten op kunt, terwijl de tijd maar één richting heeft.’

 

© Govert Schilling

 

Copyright

 

http://allesoversterrenkunde.nl/artikelen/1004-Doorbraak-...

 

 

18-09-10

Astronomen nemen afscheid van oerknalsatelliet WMAP !

 

13 september 2010

 

copyright

 

allesoversterrenkunde.nl

 

http://allesoversterrenkunde.nl/nieuws/4117-Astronomen-ne...

 

WMAP.jpg

 

Zonder veel ophef hebben astronomen op 8 september afscheid genomen van de Wilkinson Microwave Anisotropy Probe, beter bekend als WMAP.

 

De satelliet, die negen jaar lang de zogeheten kosmische achtergrondstraling heeft onderzocht, is met zijn eigen raketmotor in een veilige baan om de zon gemanoeuvreerd.

 

De WMAP-satelliet werd op 30 juni 2001 gelanceerd naar 'vaste' locatie die vanaf de zon gezien anderhalf miljoen kilometer achter de aarde ligt.

 

Enkele maanden later begon hij met het in kaart brengen van de kosmische achtergrondstraling - de straling die een overblijfsel is van de oerknal, die bijna veertien miljard jaar geleden het ontstaan van het heelal inluidde.

 

Al in 2003 werd WMAP door het wetenschappelijke tijdschrift Science uitgeroepen tot 'doorbraak van het jaar'.

 

De resultaten van de WMAP-metingen zijn in overeenstemming met het standaardmodel dat vrijwel alle astronomen voor het ontstaan van het heelal hanteren.

 

Vastgesteld is dat de oerknal waaruit ons heelal is voortgekomen 13,73 miljard jaar geleden moet hebben plaatsgevonden.

 

Ook is uit het onderzoek gebleken dat het heelal voor slechts 4,6 procent uit normale materie bestaat.

 

 

 

UniversePie.jpg

De overige 95,4 procent wordt gevormd door donkere materie, die geen enkele vorm van waarneembare straling uitzendt maar wel zwaartekracht uitoefent, en een mysterieuze donkere energie, die het heelal versneld laat uitdijen.

 

Toegevoegd door Eddy Echternach

 

www.astronieuws.nl

 

Links

 

http://nl.wikipedia.org/wiki/Wilkinson_Microwave_Anisotro...

 

http://map.gsfc.nasa.gov/

12-09-10

Laws of physics may change across the universe

 

18:29 08 September 2010 by Michael Brooks

 

New evidence supports the idea that we live in an area of the universe that is "just right" for our existence.

 

The controversial finding comes from an observation that one of the constants of nature appears to be different in different parts of the cosmos.

 

If correct, this result stands against Einstein's equivalence principle, which states that the laws of physics are the same everywhere.

 

"This finding was a real surprise to everyone," says John Webb of the University of New South Wales in Sydney, Australia.

 

Webb is lead author on the new paper, which has been submitted to Physical Review Letters.

 

Even more surprising is the fact that the change in the constant appears to have an orientation, creating a "preferred direction", or axis, across the cosmos.

 

That idea was dismissed more than 100 years ago with the creation of Einstein's special theory of relativity.

 

Sections of sky

 

At the centre of the new study is the fine structure constant, also known as alpha.

 

This number determines the strength of interactions between light and matter.

 

A decade ago, Webb used observations from the Keck telescope in Hawaii to analyse the light from distant galaxies called quasars.

 

The data suggested that the value of alpha was very slightly smaller when the quasar light was emitted 12 billion years ago than it appears in laboratories on Earth today.

 

Now Webb's colleague Julian King, also of the University of New South Wales, has analysed data from the Very Large Telescope (VLT) in Chile, which looks at a different region of the sky.

 

The VLT data suggests that the value of alpha elsewhere in the universe is very slightly bigger than on Earth.

 

The difference in both cases is around a millionth of the value alpha has in our region of space, and suggests that alpha varies in space rather than time. "

 

I'd quietly hoped we'd simply find the same thing that Keck found," King says. "This was a real shock."

 

 

Galaxies merging.jpg

 

 

 

 

 

 

 

 

 

 

 

Bar magnet

 

Moreover, the team's analysis of around 300 measurements of alpha in light coming from various points in the sky suggests the variation is not random but structured, like a bar magnet. The universe seems to have a large alpha on one side and a smaller alpha on the other.

 

This "dipole" alignment nearly matches that of a stream of galaxies mysteriously moving towards the edge of the universe.

 

It does not, however, line up with another unexplained dipole, dubbed the axis of evil, in the afterglow of the big bang.

Earth sits somewhere in the middle of the extremes for alpha. If correct, the result would explain why alpha seems to have the finely tuned value that allows chemistry – and thus life – to occur. Grow alpha by 4 per cent, for instance, and the stars would be unable to produce carbon, making our biochemistry impossible.

 

Extraordinary claim

 

Even if the result is accepted for publication, it is going to be hard to convince other scientists that the laws of physics might need a rewrite.

 

A spatial variation in the fine-structure constant would be "truly transformative", according to Lennox Cowie,

who works at the Institute for Astronomy in Hawaii.

 

But, he adds, extraordinary claims require extraordinary evidence: "That's way beyond what we have here."

 

He says the statistical significance of the new observations is too small to prove that alpha is changing.

 

If the interpretation of the light is correct, it is "a huge deal", agrees Craig Hogan, head of the Fermilab Center for Particle Astrophysics in Batavia, Illinois.

 

But like Cowie, he suspects there is a flaw somewhere in the analysis. "I think the result is not real," he says.

 

Another author on the paper, Michael Murphy of Swinburne University in Australia, understands the caution.

 

But he says the evidence for changing constants is piling up. "We just report what we find, and no one has been able to explain away these results in a decade of trying," Murphy told New Scientist.

 

"The fundamental constants being constant is an assumption. We're here to test physics, not to assume it."

 

Updated on 9 September: The analysis of VLT data was amended to credit Julian King

 


COPYRIGHT :


http://www.newscientist.com/article/dn19429-laws-of-physi...

18-08-10

Phantom Universe - Next Biggest Mystery

Analysis by Ray Villard

 

Mon Aug 16, 2010 04:27 PM ET

 

Lisa.jpg

 


It’s sort of the "Academy Awards" for deep space astronomy, except it only happens once every 10 years.
 


Last Friday a blue-ribbon National Academy of Sciences (NAS) committee released its recommendations for what types of telescopes astronomers should be building over the next decade.

 

This offers to Congress, NASA and the National Science Foundation an exploration roadmap sanctioned by our nation’s top researchers.
 


My colleague Nicole Gugliucci has a nice overview of the report's winners and runner-ups.

 

What’s fascinating is that a decade ago, it would have been hard to predict what would have made it to the top of the list of cosmic mysteries now confronting astronomers.

 

In the 2001 NAS Decadal Survey report, the big questions were about the age, history and expansion of the universe; understanding the formation and evolution of black holes of all sizes; studying the formation of stars and their planetary systems; and understanding how the astronomical environment affects Earth. Significant inroads were made into some of these areas, or are awaiting pursuit by telescopes now under construction.

 

Taking a closer look at the top science goals for the upcoming decade, it seems that the fundamental physics of the universe takes center stage.

 

Pie.jpg


 


The top-ranked space mission, called the Wide Field Infrared Survey Telescope (WFIRST), would use three types of observations to characterize dark energy.

 

Dark energy, an unimaginably weak energy field from the vacuum of space, is pushing the universe apart at an ever-faster rate.

 

This “dark force” is so far from what would have been predicted that Mike Turner of the University of Chicago calls it “the most embarrassing number in physics.” Therefore, it arguably is the most perplexing phenomenon ever to confront modern science.

 

As monumentally profound as this mystery is, I find it dissatisfying.

 

Scientists are delighted at putting ever-tighter error bars around their observations. 

 

If built and launched for an estimated $1.5 billion, WFIRST will help physicists eliminate some theories for dark energy.
 

 

We’ll know what dark energy isn’t. But the resulting dataset might never explain exactly what dark energy is.


Turner has even confessed that we simply may never know.

 

WFIRST will also look for Earth-like planets in the far reaches of the galaxy using a technique called microlensing.
 


This will build up the knowledge base for the abundance of Earth-sized planets in space. But, again, it’s just statistics and error bars.

 

I also find this dissatisfying because the newfound planets won’t be close enough to us for follow-on observations to see if they have habitable conditions.

 


Such a telescope will not take us any closer to answering the “L” world: Life in space.

 


The mega-space telescopes needed for that task won’t be technologically ready for at least another decade, and the 2020 NAS survey report.

 


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A brave new frontier that could burst open by the end of the decade is the ghostly realm of gravity waves. Spacetime should be ringing like a bell as black holes collide and supernova cores implode.

 

Though gravity waves have not yet been detected in ground-based experiments,
 


the NAS highly ranked the Laser Interferometer Space Antenna (LISA) because it would open up a whole new discovery space by detecting these whispers from massive objects gone wild.

 

But it will need a technological demonstrator precursor mission before anyone is willing to pony up approximately $3 billion for LISA.

 

Planned for 2012 is the European Space Agency’s  LISA Pathfinder mission that will test a series of ultra-high precision technologies on a small single spacecraft.

 


The front-runner in recommended new ground-based telescopes is the Large Synoptic Survey Telescope LSST

 

 

Large Synoptic Survey Telescope.jpg

 


(which also was on the to-do list in the last Decadal Survey). This machine is truly astronomical in every sense of the word.
 


It will essentially survey the entire sky on a weekly basis.

 

For the first time ever astronomers will have a time-lapse color movie of the universe.

 

It will capture wayward asteroids and comets, erupting stars, and anything else that moves or flashes in the night.

 

Untold wonders await. The resulting 1,000-terabyte data archive will be a “treasure trove,” the NAS report predicts.
 


Ranked lower on the space observatory list, and a disappointment to the aspirations of high-energy astrophysicists,
 


is the proposed $5 billion International X-Ray Observatory (IXO). Previously called Constellation-X,

 

it ranked higher than the LSST in the last Decadal Survey. The IXO would probe gravity in the extreme, as it behaves around distant black holes.
 


The IXO would also offer unique observational tests of dark energy and dark matter.

 

X-Ray astronomy has had a bumpy history. The first space observatory, Uhuru, opened up the X-ray universe in 1970.

 

A series of high-energy observatories followed in the late 1970s.

 

But X-ray astronomers had to wait another 20 years for the prolific Chandra X-Ray Observatory to come along.
 


But a member of the 2010 Decadal Survey stated that IXO had a “limited potential for great discoveries.” Ouch!

 

Based on this history, what will the next Decadal Survey rank in 2020?

 

I expect that by then the upcoming James Webb Space Telescope will fill in the opening chapter of the birth of stars and galaxies, by taking us back to within 200 million years of the Big Bang. But, given the fast pace of discoveries in exoplanets,

 


I think the overarching quest will be for finding habitable worlds.

 

I’m also sure that facilities like LSST will uncover remarkable new phenomena that need follow-up observations.

 

Copyright


http://news.discovery.com/space/phantom-universe-next-big...

 

 

 

 

 

 

 

 

07-08-10

Nieuw techniek ontwikkeld voor onderzoek donkere energie !

dark energy cygnus.jpg
21 juli 2010

National Radio Astronomy Observatory 
 
Radiosterrenkundigen hebben een nieuwe techniek ontwikkeld om grote kosmische structuren in kaart te brengen.
 
Met deze techniek hopen zij meer te weten komen over de geheimzinnige 'donkere energie' in het heelal (Nature, 22 juli).

'Donkere energie' is de naam die sterrenkundigen hebben gegeven aan de nog onbegrepen oorzaak van de versnellende uitdijing van het heelal.
 
Er zijn verschillende theorieën bedacht om die versnellende uitdijing te verklaren, maar tot nog toe is het niet gelukt om de verschillende kandidaten te
toetsen.

De sleutel wordt gezocht bij metingen van de grootschalige verdeling van sterrenstelsels in het heelal.

Het meten van de afstanden en snelheden van vele miljoenen sterrenstelsels is een tijdrovende klus.

Bij de nieuwe techniek, die intensity mapping wordt genoemd, wordt echter niet naar afzonderlijke sterrenstelsels gekeken,
 
maar naar de radiostraling die afkomstig is van neutraal waterstofgas uit een groot gebied dat grote aantallen stelsels omvat.

Op die manier wordt een flink stuk heelal in één keer gemeten en kan veel sneller inzicht worden verkregen in de wijze waarop grote kosmische structuren
 
zich de afgelopen miljarden jaren hebben ontwikkeld.

En met die informatie kan dan weer de 'beste' theorie voor de verklaring van de donkere energie worden geselecteerd.
 
© Eddy Echternach (www.astronieuws.nl)
Copyright
URL van deze pagina:

Links:
Radio Astronomers Develop New Technique for Studying Dark Energy

14-06-10

Dark Energy and Dark Matter Might Not Exist, Scientists Allege

By Clara MoskowitzSPACE.com Senior Writerposted: 13 June 201007:01 pm ET Dark matter and dark energy are two of the most mind-boggling ingredients in the universe. Ever since these concepts were first proposed, some astronomers have worked feverishly to figure out what each thing is, while other astronomers have tried to prove they don't exist, in hopes of restoring the universe to the more understandable place many would like it to be.A new look at the data from one of the telescopes used to establish the existence of this strange stuff is causing some scientists to question whether theyreally exist at all. Yet other experts are holding firm to the idea that, whether we like it or not, the "dark side" of the universe is here to stay.Dark matter is a proposed form of matter that could make up 22 percent of the universe's mass-energy budget, vastly outweighing all the normal matter, like stars and galaxies. Astronomers can't observe dark matter directly, but they think it's there because of the gravitational pull it seems to exert on everything else. Without dark matter, the thinking goes, galaxies would fly apart.Ads by GoogleJesus: Hoax or Reality?Discover the Evidence From Scholars About Jesus' Claims to be God www.Y-Jesus.com/GodWhy is Brazil Hot What the Banks are not saying What the Banks are investing in www.greenwood-management.comAs if that weren't weird enough, scientists think another 74 percent of themass-energy budget could be made of some strange quantity called dark energy. This force is thought to be responsible for the accelerating pace of the expansion of the universe. (For those keeping track, that would leave only a measly 4 percent of the universe composed of normal matter.)Some cosmic backgroundOne of the prime ways researchers tally how much these components contribute to the overall makeup of the universe is by measuring a dim glow of light pervading space that is thought to be left over from the Big Bang. The most detailed measurements yet taken of this radiation, which is called the cosmic microwave background (CMB), come from a spacecraft dubbed the Wilkinson Microwave Anisotropy Probe (WMAP)."It's such an important thing — the microwave background," said astrophysicist Tom Shanks of Durham University in England. "All the results in dark energy and dark matter in cosmology hang on it, and that's why I'm interested in checking the results."Recently Shanks and his graduate student Utane Sawangwit went back to examine the WMAP data and used a different method to calibrate how much smoothing,or blurring, the telescope was causing to its images. This smoothing is an expected affect, akin to the way Earth's atmosphere blurs stars' light so they twinkle.Instead of using Jupiter as a calibration source, the way the WMAP team did, Shanks and Sawangwit used distant astronomical objects in the WMAP data itself that were emitting radio light."When we checked radio sources in the WMAP background, we found more smoothing than the WMAP team expected," Shanks told SPACE.com. "That would have big implications for cosmology if we were proven right."If this smoothing error is larger than thought, it could indicate that fluctuations measured in the intensity of the CMB radiation are actually smaller than they originally appeared. The size of these fluctuations is a key parameter used to support the existence of dark matter and dark energy. With smaller ripples, there would be no need to invoke exotic concepts like dark matter and dark energy to explain the CMB observations, Shanks said.The researchers will report their findings in an upcoming issue of the journal Monthly Notices of the Royal Astronomical Society.Others not so sure !Yet other astronomers, particularly those who first analyzed the WMAP results, remain unconvinced. "The WMAP team has carried out extensive checks and we unequivocally stand by our results," said WMAP principal investigator Charles Bennett of Johns Hopkins University in Baltimore, Md.The WMAP researchers take issue with Sawangwit and Shanks' use of dim, far-away radio sources to calculate the telescope's smoothing error."These are weak sources, so many of them must be averaged together to obtain useful measurements. None of them move with respect to the CMB," said WMAP team member Mark Halpern of the University of British Columbia. "This method is inferior to our main approach."Plus, Halpern said he and his colleagues had identified an error the other team made in failing to account for the confusing contribution of the CMB ripples themselves."We can obtain the Shanks result by omitting the step that properly accounts for the background confusion, but this step is necessary," Bennett explained.Back in this corner ...Yet Shanks said he's aware of these objections and stands by his calculations. "We don't think that's an issue," he said.Ultimately, Shanks hopes future measurements of the microwave background radiation from new telescopes will help clear up the issue.The European Space Agency's Planck spacecraft, launched into orbit in 2009, is currently taking new, even more detailed observations of the CMB. "I'm very interested to see what Planck gets in terms of its results," Shanks said. "And of course we will be there to try and keep everybody as honest aspossible. We're hoping we can use our methods in the same way to check their beam profile that they ultimately come up with."copyright space.com URLhttp://www.space.com/scienceastronomy/dark-matter-dark-energy-question-100613.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+spaceheadlines+%28SPACE.com+Headline+Feed%29CMB thumbnail

11-05-10

X-ray Discovery Points to Location of Missing Matter

Scientists using two X-ray telescopes (Chandra and XMM-Newton) have found evidence for the "missing matter" in the nearby Universe. This matter is made up of hot diffuse gas, which is known as WHIM (warm-hot intergalactic medium). To get this result, researchers analyzed X-ray light from a distant quasar that passed through a "wall" of galaxies about 400 million light years from Earth.Scientists have used NASA's Chandra X-ray Observatory and ESA's XMM-Newton to detect a vast reservoir of gas lying along a wall-shaped structure of galaxiesabout 400 million light years from Earth. In this artist's impression, a close-up view of the so-called Sculptor Wall is depicted. Spiral and elliptical galaxies are shown in the wall along with the newly detected intergalactic gas, part of the so-called Warm Hot Intergalactic Medium (WHIM), shown in blue. This discovery is the strongest evidence yet that the "missing matter" in the nearby Universe is located in an enormous web of hot, diffuse gas.The X-ray emission from WHIM in this wall is too faint to be detected, so instead a search was made for absorption of light from a bright background source by the WHIM, using deep observations with Chandra and XMM. This background source is a rapidly growing supermassive black hole located far beyond the wall at a distance of about two billion light years. This is shown in the illustration as a star-like source, with light traveling through the Sculptor Wall towards the Earth. The relative location of the background source, the Sculptor Wall, and the Milky Way galaxy are shown in a separate plot, where the view instead looks down on the source and the Wall from above.An X-ray spectrum of the background source is given in the inset, where the yellow points show the Chandra data and the red line shows the best model for the spectrum after including all of the Chandra and XMM data. The dip in X-rays towards the right side of the spectrum corresponds to absorption by oxygen atoms in the WHIM contained in the Sculptor Wall.The characteristics of the absorption are consistent with the distance of the Sculptor Wall as well as the predicted temperature and density of the WHIM.This result gives scientists confidence that the WHIM will also be found in other large-scale structures.This result supports predictions that about half of the normal matter in the local Universe is found in a web of hot, diffuse gas composed of the WHIM. Normal matter — which is different from dark matter -- is composed of the particles, such as protons and electrons, that are found on the Earth, in stars, gas, and so on. A variety of measurements have provided a good estimate of the amount of this "normal matter" present when the Universe was only a few billion years old. However, an inventory of the nearby Universe has turned up only about half as much normal matter, an embarrassingly large shortfall.COPYRIGHT : Chandra X Ray telescope URLhttp://chandra.harvard.edu/photo/2010/h2356/chandra

02-05-10

Donkere materie in kaart gebracht

26 april 2010Subaru Telescope Een internationaal team van sterrenkundigen heeft voor het eerst de verdeling van donkere materie in clusters van sterrenstelsels duidelijk in kaart gebracht. Uit hun onderzoek blijkt dat deze verdeling eerder de vorm van een rugbybal heeft dan die van een voetbal. En dat is precies wat op theoretische gronden werd verwacht. Bij het opsporen van de donkere materie, die zoals de naam als suggereert niet rechtstreeks waarneembaar is, is gebruik gemaakt van het zogeheten gravitatielenseffect. Dat effect is het gevolg van de licht-afbuigende werking van materie. Door heel nauwkeurig te onderzoeken hoe sterk een verre cluster van sterrenstelsels het licht van nog verder weg gelegen objecten afbuigt, kan worden vastgesteld hoe de materie in zo'n cluster is verdeeld. Op die manier hebben Japanse, Taiwanese en Britse sterrenkundigen met de Subaru-telescoop op Hawaï twintig clusters onderzocht. Daarbij is gebleken dat de verdeling van de donkere materie de vorm heeft van een afgeplatte bol. En dat is in overeenstemming met de heersende gedachte dat donkere materie uit zogeheten WIMP's bestaat: traag bewegende, zware deeltjes die een overblijfsel zijn van de oerknal. © Eddy Echternach (www.astronieuws.nl)COPYRIGHT ALLES OVER STERRENKUNDE EN SUBARU TELESCOPE !!URL http://allesoversterrenkunde.nl/nieuws/3918-Donkere-materie-in-kaart-gebracht.htmlURL SUBARU TELESCOPEhttp://www.subarutelescope.org/Pressrelease/2010/04/26/index.htmlfeat_beyondgalileo_diag_zoom

30-04-10

Lightening the dark

About 96% of the Universe is in the form of unknown matter and energy. The rest – only 4% – is the ‘ordinary matter’ that we are made of and that makes up all the planets, the stars and the galaxies we observe. The LHC experiments have the potential to discover new particles that could make up a large fraction of the Universe.In recent years, scientists have collected various evidence of the existence of a new type of matter in the Universe. They call it ‘dark’ because it does not emit or absorb electromagnetic radiation. "One of the main proofs of its existence comes from the measurement of the rotational speed of astronomical bodies in spiral galaxies", explains Gian Giudice, a member of CERN's Theory group and the author of "A Zeptospace Odyssey", a recent book on LHC physics aimed at the general public.According to the Newtonian laws of motion, this value varies as a function of the distance from the centre of the galaxy: more distant objects should rotate at a lower speed than those situated nearer the centre. However, back in the 1970s, astronomers found that outer stars move at a higher rotational speed than expected. “With such a velocity, the attractive gravitational force exerted by the observable mass would not be enough to keep those stars in the galaxy,and stars would simply escape”, continues Gian Giudice. Therefore, something must exist that keeps the galaxy together by exerting gravitational attraction."The second strong piece of evidence suggesting the existence of dark matter comes from the 'gravitational lensing' effect, in which galactic clusters bend the light coming from more distant objects. The way the light is deviated shows that the total mass contained in the clusters must be much larger than what we observe”, explains Giudice. Moreover, studies on the way in which the initial atoms and molecules formed in the Universe show that ordinary matter cannot account for more than 4% of the Universe. This fact allows scientists to exclude the possibility that invisible matter is made of massive objects such as Jupiter-sized planets. On the other hand, theory and observations do not exclude that dark matter is made of primordial black holes in which large amounts of matter could be trapped. However, this latter possibility seems very remote, and scientists tend to think that dark matter is made of a new type of particle.How could the LHC help enlighten physicists?"The yet undiscovered dark matter has to meet some requirements imposed by observations and theory", says Gian Giudice. "It has to be stable, it has to carry no charge, and it has to be relatively heavy”.Through studies on the evolution of the Universe, scientists have been able to infer the mass of the dark matter constituents, situating it between 100 GeV and 1 TeV (for reference, the mass of the proton is about 1 GeV). Interestingly enough, this is exactly the same mass range in which theories beyond the Standard Model anticipate the existence of new particles.“The LHC will explore exactly that range of energies. Therefore, if new particles exist, the LHC has a big chance of finding them”, confirms Gian Giudice. He adds: “The theoretical supersymmetric model suggests three possible candidates for dark matter: the neutralino, the gravitino and the sneutrino. However, it is important to note that supersymmetry is not the only possible scenario".Besides the whole plethora of possible alternative scenarios, even if the LHC experiments find evidence of new particles, it will not be possible to claim that they are the actual components of dark matter. For this, confirmation will be needed from other dedicated experiments.From deep inside the Earth to outer spaceOther experiments are searching for the elusive dark matter particles. Some of them, such as the CDMS experiment at the Soudan Underground Laboratory in Minnesota, and the XENON and DAMA experiments at the Gran Sasso Laboratory in Italy, are installed underground. Others, such as Pamela and Fermi (also at Gran Sasso), are in orbit around our planet.by Francesco PoppiCopyright CERN 2010 - CERN Publications, DG-COhttp://cdsweb.cern.ch/journal/CERNBulletin/2010/18/News%20Articles/1261775?ln=enbild_LHC_Cern

27-04-10

Cosmic Dark Matter Clumps Into Cigar Shapes

By Clara MoskowitzSPACE.com Senior Writerposted: 26 April 201003:09 pm ETElusive dark matter around clusters of galaxies often clumps into cigar shapes, new observations show.The discovery could help scientists finally understand what makes up dark matter, which is the mystifying stuff thought to exist invisibly all around us. Dark matter, which could be more than five times more abundant than visible matter, is only detectable through its gravitational pull on regular material.According to the new observations, the dark matter around many galaxy clusters is a flattened, cigar-like shape, rather than a rounded sphere."There are clear theoretical predictions that we expect dark mater haloes to be flattened like this," said study co-author Graham P. Smith of the U.K.'s University of Birmingham. "It's a very beautiful, very clean and direct measurement of that."Smith and the team, led by Masamune Oguri of the National Astronomical Observatory of Japan and Masahiro Takada at the University of Tokyo, used a quirk of gravity called gravitational lensing to observe dark matter's gravitational effects on large collections of galaxies known as galaxy clusters. Gravitational lensing occurs when mass warps space-time, causing light to travel along a curved path when it passes by. The amount of curving can tell astronomers how massive celestial objects are.For this study, the researchers used the Prime Focus Camera on the Subaru Telescope on Mauna Kea in Hawaii to observe 20 galaxy clusters. They took advantage of gravitational lensing to create maps of the distribution of mass around the clusters, thus getting a peek into the secrets of dark matter."What we're probing with these gravitational lensing observations is the dark matter distribution, because the dark matter dominates the mass on these large scales," Smith told SPACE.com.The fact that the dark matter seems to be flattened out into oblong shapes fits in with the so-called cold dark matter theory. Computer simulations based on this theory have predicted such shapes, but they have never before been verified to such an extent with so many large clusters.The findings could shed light on the fundamental nature of this weird stuff, which scientists cannot detect directly. The observations support the possibility that dark matter is actually made of tiny particles called WIMPS (weakly-interacting massive particles) that exert a strong gravitational force, but otherwise don't interact with normal matter.The research will be detailed in the Monthly Notices of the Royal Astronomical Society.Copyright SPACE.comhttp://www.SPACE.com/scienceastronomy/dark-matter-galaxy-clusters-100426.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+spaceheadlines+%28SPACE.com+Headline+Feed%29&utm_content=Google+Reader080923-galaxy-cluster-02

16-04-10

ANTIMATTER - WHERE DID IT ALL GO ?

For many years, the absence of antimatter in the Universe has tantalised particle physicists and cosmologists: while the Big Bang should have created equal amounts of matter and antimatter, we do not observe any primordial antimatter today. Where has it gone? The LHC experiments have the potential to unveil natural processes that could hold the key to solving this paradox. Every time that matter is created from pure energy, equal amounts of particles and antiparticles are generated. Conversely, when matter and antimatter meet, they annihilate and produce light. Antimatter is produced routinely when cosmic rays hit the Earth's atmosphere, and the annihilations of matter and antimatter are observed during physics experiments in particle accelerators. If the Universe contained antimatter regions, we would be able to observe intense fluxes of photons at the boundaries of the matter/antimatter regions. “Experiments measuring the diffuse gamma-ray background in the Universe would be able to observe these light emissions”, confirms Antonio Riotto of CERN's Theory group. “In the absence of such evidence, we can conclude that matter domains are at least the size of the entire visible Universe”, he adds. What caused the disappearance of antimatter in favour of matter? “In 1967, the Russian physicist Andrej Sakharov pointed out that forces discriminating between matter and antimatter, called “CP-violating” effects, could have modified the initial matter-antimatter symmetry when deviations from the thermal equilibrium of the Universe occured”, says Antonio Riotto. In the cold Universe today, we can only observe very rare CP-violating effects in which Nature prefers the creation of matter over antimatter. Following their discovery in the decays of K-mesons containing strange quarks, they have now also been observed in the decays of B mesons, which contain bottom quarks. Today, scientists think that the early Universe might have gone through a transition phase in which the thermodynamic equilibrium was broken, when the density of the Universe was very high and the average temperature was one billion or more times that inside the Sun. "Some physicists think that this might have happened through the formation of ‘bubbles’ which have progressively expanded, thus ‘imposing’ their new equilibrium on the whole pre-existent Universe", explains Antonio Riotto. Whatever the real dynamics of this phase actually were, the important thing is that one particle of matter in every 10 billion survived, while all the others annihilated with the corresponding antiparticles. How can the LHC help to solve the mystery? By studying rare decays, experiments can bring us more accurate information about phenomena related to CP-violation involving both known and new particles, such as mesons containing both bottom and strange quarks. Moreover, if new supersymmetric particles are discovered at the LHC, some of the possible scenarios leading to a non-equilibrium phase could find experimental support. "If the LHC finds a Higgs boson with a mass less than about 130 GeV, and if this discovery comes with the detection of a light supersymmetric particle called ‘stop‘, this could be the experimental proof that the non-equilibrium phase happened through the formation of bubbles", concludes Antonio Riotto. In any case, since the disappearance of primordial antimatter cannot be explained by the current Standard Model theory, it is clear that we have to look for something new. Scientists are exploring different avenues but, given the fact that what we observe represents only about 4% of the total energy and matter that the Universe is made of, one can guess that part of the key to solving the antimatter mystery could be held in the yet unknown part of the Universe. With its very high discovery potential, the LHC will certainly help shed light on the whole issue.antimatterCOPYRIGHT CERN BULLETIN URL :http://cdsweb.cern.ch/journal/CERNBulletin/2010/16/News%20Articles/1255394?ln=en

07-02-10

Distant Galaxies Unlock New Secrets of Dark Matter

dark matterTo weigh the universe, scientists use two kinds of cosmic scales: one to measure all the regular matter out there, and another to deduce how much invisible dark matter remains hidden underneath.These calculations have been taken further than ever before by a new study that tallied both types of mass in smaller and more distant groups of galaxies than any previous projects. The project found that these faraway galactic clusters have roughly the same proportion of dark matter to regular matter as the closer galaxy groups do.The findings could help astronomers understand more about dark matter, as well as its even stranger sibling – dark energy.Invisible universeDark matter is a form of stuff that does not interact with light, so cannot be seen, but makes its presence felt by exerting a gravitational pull on normal matter.Astronomers measure how much dark matter lies in galaxies by a fluke of physics called gravitational lensing. This phenomenon, predicted by Einstein's theory of general relativity, causes light to curve as it flies through space-time that has been dented by the gravity of large bodies of mass. For example, groups of massive galaxies will gravitationally warp the space-time around them, forcing light to bend as it passes through, and causing them to look distorted when their light reaches our telescopes. Scientists can tell how much total mass there is by how much of this distortion occurs.Next, researchers calculate how much normal matter is in a cluster of galaxies by looking at its X-ray light, since the light must be coming from only the regular stars and gas that make up the cluster.Comparing these two calculations — the total matter to just the regular matter — gives a ratio astronomers call the mass-luminosity relation. So far, the mass-luminosity relation has been measured well for nearby, large galaxy clusters, but there has not been good enough X-ray data to probe farther or smaller, dimmer clusters of galaxies."We can map out the big cities, but no one's been able to map out the villages yet," said Alexie Leauthaud of the Lawrence Berkeley National Laboratory in Berkeley, Calif., leader of the new study.New rangesAstronomers used observations from the European Space Agency's XMM-Newton satellite and from NASA's Chandra satellite, as well as data from the Hubble Space Telescope's Cosmic Evolution Survey (COSMOS). These ultra-high resolution photos allowed the scientists to extend the mass-luminosity relation further than ever before.With such dim objects, the gravitational lensing wasn't immediately apparent. So researchers used a statistical analysis to measure the orientation and shape of the galaxies to find small distortions due to so-called weak lensing.They found that the same general ratio of dark matter to normal matter prevailed in these distant, small clusters as for nearby, larger clusters."We didn't know what to expect going down to lower masses or [farther distances], and we find this nice simple relationship," Leauthaud told SPACE.com. "Now the aim is to find out why we find this nice, simple relationship."Dark energy enigmaThe finding may help shed light on an even more bizarre aspect of the universe — dark energy. Dark energy is the name given to whatever mysterious force is causing the universe to accelerate as it expands."We want to try to understand the properties of dark energy," Leauthaud said. "One way to measure properties of dark energy is to measure the number of structures that have formed for a given amount of dark matter."Dark energy basically works against gravity in a tug-of-war. While gravity constantly pulls mass inward, encouraging things to clump together and condense into smaller space, dark energy does the opposite. This force somehow pulls everything apart, causing everything in the universe to move away from everything else at ever-increasing speeds.When mass clumps together enough to form galaxies, it means that gravity has won on those scales, helping things to stick together despite the pull of dark energy. So the more astronomers can measure when and how structures formed in the universe, the better they can understand just how far dark energy's pull reaches.Copyright http://www.space.com/scienceastronomy/dark-matter-galaxy-clusters-100126.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+spaceheadlines+%28SPACE.com+Headline+Feed%29&utm_content=Google+Reader

29-12-09

Neutrino May Have Triggered Dark Energy 28122008

CompositionCosmos_550CompositionCosmos_550A new theory may explain the mysterious force that is causing our universe to expand at a faster and faster rate. By Irene Klotz | Mon Dec 28, 2009 10:05 AM ET Seventy-five percent of the universe's mass and/or energy must be comprised of dark energy to explain the universe's observed rate of acceleration.NASA/CXC/UCLA/M. Muno et al.Could a neutrino -- an electrically neutral and nearly mass-free sibling to the electron -- have triggered dark energy, the anti-gravity force discovered just over a decade ago?That's the latest idea from a team of theoretical physicists who suggest that dark energy was created from neutrino condensate in the split second after the universe's birth 13.7 billion years ago.The idea sprang from calculations showing that the density of dark energy is comparable to the value of neutrino mass, said lead researcher Jitesh Bhatt, with the Physical Research Laboratory in Ahmedabad, India.Dark energy, an unknown force that is accelerating the expansion of the universe, is the leading cosmological mystery of modern-day science.It was discovered in 1998 after astrophysicists noted that supernovae -- the exploded remains of massive stars -- showed an accelerated rate of expansion in the last 2 billion years or so when compared to older epochs. Explanations for dark energy fall into two basic camps: those theories that add a new physical entity or those that change the laws of gravity, said Eric Linder with the University of California at Berkeley."If you search for 'dark energy' in just the titles (of research papers) in the past year, you will find 200 speculations on what dark energy is," Linder wrote in an email to Discovery News. "There are a great many hypotheses for dark energy. Some ties to neutrinos have been considered for the last several years, but nothing substantial has yet come out of them."To account for the universe's observed rate of acceleration, 75 percent of the mass and/or energy of the universe has to be comprised of a gravitationally repulsive force, or dark energy.Scientists are developing several dark energy experiments, including the NASA/Department of Energy Joint Dark Energy Mission, in an attempt to refine dark energy measurements and reveal how it operates."It will take much more work before we can pin down the nature of dark energy," Bhatt said. "Without knowing the nature of the dark energy, our knowledge of theoretical physics would remain incomplete."Bhatt's research was published in last month's issue of Physical Review D.copyright http://news.discovery.com/videos/space-study-sheds-light-on-dark-energy.htmlCompositionCosmos_550

22-12-09

Mystery Swirls Around 'Dark Stars'

By Charles Q. ChoiSPECIAL to SPACE.composted: 21 December 200908:21 am ETWhen the very first stars lit up, they may have been fueled by the dark matter that has long eluded scientists.These "dark stars," first born nearly 13 billion years ago, might still exist today. Although they would not shed any visible light, astronomers might detect these invisible giants — some 400 to 200,000 times wider than our sun and 500 to 1,000 times more massive — because they should spew gamma rays, neutrinos and antimatter and be linked with clouds of cold, molecular hydrogen gas that normally would not harbor such energetic particles.If scientists find these stars, they could aid the search to discover and identify dark matter. They could also help solve the mystery of why black holes formed much faster than expected.Scientists think unseen, as-yet unidentified dark matter makes up about 95 percent of all matter in the universe. They know it exists because galaxies rotate faster than can be explained by the visible matter within them. Among the main candidates for what dark matter is are WIMPs, or weakly interacting massive particles. One type of WIMP that scientists theorize exists is called a neutralino. These particle can annihilate each other, generating heat. They would also produce quarks and their antimatter counterparts, antiquarks, which would collide to emit gamma rays, neutrinos and antimatter such as positrons and antiprotons.The researchers calculated that in the newborn universe, some 80 to 100 million years after the Big Bang, as proto-stellar clouds of hydrogen and helium tried to cool and shrink, annihilating neutralinos would have kept them hot and large. The result might be dark stars, fueled by dark matter instead of nuclear energy as in normal stars. These would have been made up largely of normal matter, mostly in the form of hydrogen and helium, but would be vastly larger and fluffier than the sun and current stars."It's a completely new type of star with a new power source," said researcher Katherine Freese, a theoretical physicist at the University of Michigan.Originally researcher Paolo Gondolo, a particle astrophysicist at the University of Utah, wanted to dub these new, theoretical kinds of invisible stars "brown giants," similar to dim but smaller, Jupiter-sized stars known as "brown dwarfs." But he said his collaborators insisted on calling them "dark stars," after the song "Dark Star" first played in 1967 by the revered rock band The Grateful Dead. "There is a dark star song by Crosby, Stills, Nash and Young, too, that we had in mind," Freese said."It was a good name," Gondolo noted. Although dark stars are made up  of less than 1 percent dark matter, "it's very important," he explained. "It converts all of its mass to energy with 100 percent efficiency, under Einstein's equation, E=mc2. Normal stars that rely on nuclear energy convert just a small fraction of its mass to energy, 1 or 2 percent."There was initially skepticism as to whether dark matter densities were high enough in the early universe to support the creation of dark stars. "However, we've checked it and so have two other groups, and they agree with us," Freese said. Dark stars could be detected with the next-generation James Webb Space Telescope currently scheduled for launch in 2014. "It may be that these stars eventually cluster together, and clusters of them might be visible with the James Webb Space Telescope," Gondolo said.If scientists do discover dark stars, "they would tell us a very important thing — that dark matter is made of elementary particles," Gondolo said. "At this moment, we know absolutely nothing about what dark matter is made of. We know where dark matter is, how much is there, but we don't know its nature."Dark stars might also explain why black holes formed much faster than expected. Astronomers have found black holes that existed only a few hundred million years after the Big Bang, yet current theories suggest they should have taken longer to form. Dark stars might have collapsed into black holes very early, Gondolo said, because they might be very short-lived and could have formed when the universe was young.In addition, dark stars could solve a puzzle seen with stars in the galactic halo, the murky, roughly spherical part of the galaxy extending past the main, visible component. "There's an abundance of elements in the very old halo stars that's hard to explain, and dark stars can explain that — they would end up creating the chemical abundances needed," Gondolo said.It is unlikely any dark stars are being formed today, Freese said."The early universe was more compact than it is now, and everything was denser, including the amount of dark matter one had at any one place," she explained. "Now the universe has expanded and things are less dense, making it harder to make dark stars today."It remains uncertain just how long dark stars might live, Freese said."The ones that formed in the early universe could have continued as long as they had dark matter to power them," Freese said. "They start at the center of dark matter 'halos' — giant spherical globes of dark matter — and these are always merging with other ones, so some might have burned out their dark matter fuel very early and become either normal stars or collapsed, but it remains an open question if any have survived until now."copyright : Space,com http://www.space.com/scienceastronomy/091221-mm-dark-stars.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+spaceheadlines+%28SPACE.com+Headline+Feed%29&utm_content=Google+ReaderDark Star