Laws of Physics Vary Throughout the Universe, New Study Suggest

Laws of Physics Vary Throughout the Universe, New Study Suggest

  10:21:00 AM    Science Lover

---

A team of astrophysicists based in Australia and England has uncovered evidence that the laws of physics are different in different parts of the universe.

Illustration of the dipolar variation in the fine-structure constant, alpha, across the sky, as seen by the two telescopes used in the work: the Keck telescope in Hawaii and the ESO Very Large Telescope in Chile. (Credit: Copyright Dr. Julian Berengut, UNSW, 2010)

The team -- from the University of New South Wales, Swinburne University of Technology and the University of Cambridge -- has submitted a report of the discovery for publication in the journal Physical Review Letters. A preliminary version of the paper is currently under peer review.

The report describes how one of the supposed fundamental constants of Nature appears not to be constant after all. Instead, this 'magic number' known as the fine-structure constant -- 'alpha' for short -- appears to vary throughout the universe.

"After measuring alpha in around 300 distant galaxies, a consistency emerged: this magic number, which tells us the strength of electromagnetism, is not the same everywhere as it is here on Earth, and seems to vary continuously along a preferred axis through the universe," Professor John Webb from the University of New South Wales said.

"The implications for our current understanding of science are profound. If the laws of physics turn out to be merely 'local by-laws', it might be that whilst our observable part of the universe favours the existence of life and human beings, other far more distant regions may exist where different laws preclude the formation of life, at least as we know it."

"If our results are correct, clearly we shall need new physical theories to satisfactorily describe them."

The researchers' conclusions are based on new measurements taken with the Very Large Telescope (VLT) in Chile, along with their previous measurements from the world's largest optical telescopes at the Keck Observatory in Hawaii.

Mr Julian King from the University of New South Wales explained how, after combining the two sets of measurements, the new result 'struck' them. "The Keck telescopes and the VLT are in different hemispheres -- they look in different directions through the universe. Looking to the north with Keck we see, on average, a smaller alpha in distant galaxies, but when looking south with the VLT we see a larger alpha."

"It varies by only a tiny amount -- about one part in 100,000 -- over most of the observable universe, but it's possible that much larger variations could occur beyond our observable horizon," Mr King said.

The discovery will force scientists to rethink their understanding of Nature's laws. "The fine structure constant, and other fundamental constants, are absolutely central to our current theory of physics. If they really do vary, we'll need a better, deeper theory," Dr Michael Murphy from Swinburne University said.

"While a 'varying constant' would shake our understanding of the world around us extraordinary claims require extraordinary evidence. What we're finding is extraordinary, no doubt about that."

"It's one of the biggest questions of modern science -- are the laws of physics the same everywhere in the universe and throughout its entire history? We're determined to answer this burning question one way or the other."

Other researchers involved in the research are Professor Victor Flambaum and PhD student Matthew Bainbridge from the University of New South Wales, and Professor Bob Carswell at the University of Cambridge (UK).

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Swinburne University of Technology.

Read More

Galactic Magnifying Lens to Probe Elusive Dark Energy

Galactic Magnifying Lens to Probe Elusive Dark Energy

  10:26:00 AM    Science Lover

---

An international team of astronomers using gravitational lensing observations from the NASA/ESA Hubble Space Telescope has taken an important step forward in the quest to solve the riddle of dark energy, a phenomenon which mysteriously appears to power the Universe's accelerating expansion.

This image shows the galaxy cluster Abell 1689, with the 
mass distribution of the gravitational lens overlaid 
(in purple). The mass in this lens is made up partly of normal 
(baryonic) matter and partly of dark matter. Distorted 
galaxies are clearly visible around the edges of the 
gravitational lens. The appearance of these distorted galaxies 
depends on the distribution of matter in the lens and on the 
relative geometry of the lens and the distant galaxies, as well
as on the effect of dark energy on the geometry of the universe. 
(Credit: NASA, ESA, E. Jullo (JPL/LAM), P. 
Natarajan (Yale) and J-P. Kneib (LAM).)

Their results appear in the 20 August 2010 issue of the journal Science.

Normal matter like that found in stars, planets and dust clouds only makes up a tiny fraction of the mass-energy content of the Universe. It is dwarfed by the amount of dark matter -- which is invisible, but can be detected by its gravitational pull. In turn, the amount of dark matter in the Universe is itself overwhelmed by the diffuse dark energy that permeates the entire Universe. Scientists believe that the pressure exerted by this dark energy is what pushes the Universe to expand at an ever-increasing rate.

Probing the nature of dark energy is, therefore, one of the key challenges in modern cosmology. Since its discovery in 1998, the quest has been to characterise and understand it better. This work presents an entirely new way to do so.

Eric Jullo, lead author of a new paper in the journal Science explains: "Dark energy is characterised by the relationship between its pressure and its density: this is known as its equation of state. Our goal was to try to quantify this relationship. It teaches us about the properties of dark energy and how it has affected the development of the Universe."

The team measured the properties of the gravitational lensing in the galaxy cluster Abell 1689. Gravitational lensing is a phenomenon predicted by Einstein's theory of general relativity, and was here used by the team to probe how the cosmological distances (and thus the shape of space-time) are modified by dark energy. At cosmic distances, a huge cluster of galaxies in the foreground has so much mass that its gravitational pull bends beams of light from very distant galaxies, producing distorted images of the faraway objects. The distortion induced by the lens depends in part on the distances to the objects, which have been precisely measured with large ground-based telescopes such as ESO's Very Large Telescope and the Keck Telescopes.

"The precise effects of lensing depend on the mass of the lens, the structure of space-time, and the relative distance between us, the lens and the distant object behind it," explains Priyamvada Natarajan, a co-author of the paper. "It's like a magnifying glass, where the image you get depends on the shape of the lens and how far you hold it from the object you're looking at. If you know the shape of the lens and the image you get, you can work out the path that light followed between the object and your eye."

Looking at the distorted images allows astronomers to reconstruct the path that light from distant galaxies takes to make its long journey to Earth. It also lets them study the effect of dark energy on the geometry of space in the light path from the distant objects to the lensing cluster and then from the cluster to us. As dark energy pushes the Universe to expand ever faster, the precise path that the light beams follow as they travel through space and are bent by the lens is subtly altered. This means that the distorted images from the lens encapsulate information about the underlying cosmology, as well as about the lens itself.

So why is the geometry of the Universe such a big issue?

"The geometry, the content and the fate of the Universe are all intricately linked," says Natarajan. "If you know two, you can deduce the third. We already have a pretty good knowledge of the Universe's mass-energy content, so if we can get a handle on its geometry then we will be able to work out exactly what the fate of the Universe will be."

The real strength of this new result is that it devises a totally new way to extract information about the elusive dark energy. It is a unique and powerful one, and offers great promise for future applications.

According to the scientists, their method required multiple, meticulous steps to develop. They spent several years developing specialised mathematical models and precise maps of the matter -- both dark and "normal" -- that together constitute the Abell 1689 cluster.

Co-author Jean-Paul Kneib explains: "Using our unique method in conjunction with others, we were able to come up with results that were far more precise than any achieved before."

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of Eric Jullo (Jet Propulsion Laboratory/ Cal Tech, USA and Laboratoire d'Astrophysique de Marseille, France), Priyamvada Natarajan (Yale University, USA), Jean-Paul Kneib (Laboratoire d'Astrophysique de Marseille, France), Anson D'Aloisio (Yale University, USA), Marceau Limousin (Laboratoire d'Astrophysique de Marseille, France and University of Copenhagen, Denmark), Johan Richard (Durham University, UK) and Carlo Schimd (Laboratoire d'Astrophysique de Marseille, France)

Read More

How Much Mass Makes a Black Hole? Astronomers Challenge Current Theories

How Much Mass Makes a Black Hole? Astronomers Challenge Current Theories

  7:27:00 PM    Science Lover

---

Using ESO's Very Large Telescope, European astronomers have for the first time demonstrated that a magnetar -- an unusual type of neutron star -- was formed from a star with at least 40 times as much mass as the Sun. The result presents great challenges to current theories of how stars evolve, as a star as massive as this was expected to become a black hole, not a magnetar. This now raises a fundamental question: just how massive does a star really have to be to become a black hole?

This artist's impression shows the magnetar in 
the very rich and young star cluster Westerlund 1. 
This remarkable cluster contains hundreds of very 
massive stars, some shining with a brilliance of almost 
one million suns. European astronomers have for the 
first time demonstrated that this magnetar -- an unusual 
type of neutron star with an extremely strong magnetic 
field -- was formed from a star with at least 40 times as 
much mass as the Sun. The result presents great challenges 
to current theories of how stars evolve, as a star as 
massive as this was expected to become a black 
hole, not a magnetar. (Credit: ESO/L. Calçada)

To reach their conclusions, the astronomers looked in detail at the extraordinary star cluster Westerlund 1, located 16 000 light-years away in the southern constellation of Ara (the Altar). From previous studies, the astronomers knew that Westerlund 1 was the closest super star cluster known, containing hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two thousand times the diameter of the Sun (as large as the orbit of Saturn).

"If the Sun were located at the heart of this remarkable cluster, our night sky would be full of hundreds of stars as bright as the full Moon," says Ben Ritchie, lead author of the paper reporting these results.

Westerlund 1 is a fantastic stellar zoo, with a diverse and exotic population of stars. The stars in the cluster share one thing: they all have the same age, estimated at between 3.5 and 5 million years, as the cluster was formed in a single star-formation event.

A magnetar is a type of neutron star with an incredibly strong magnetic field -- a million billion times stronger than that of the Earth, which is formed when certain stars undergo supernova explosions. The Westerlund 1 cluster hosts one of the few magnetars known in the Milky Way. Thanks to its home in the cluster, the astronomers were able to make the remarkable deduction that this magnetar must have formed from a star at least 40 times as massive as the Sun.

As all the stars in Westerlund 1 have the same age, the star that exploded and left a magnetar remnant must have had a shorter life than the surviving stars in the cluster. "Because the lifespan of a star is directly linked to its mass -- the heavier a star, the shorter its life -- if we can measure the mass of any one surviving star, we know for sure that the shorter-lived star that became the magnetar must have been even more massive," says co-author and team leader Simon Clark. "This is of great significance since there is no accepted theory for how such extremely magnetic objects are formed."

The astronomers therefore studied the stars that belong to the eclipsing double system W13 in Westerlund 1 using the fact that, in such a system, masses can be directly determined from the motions of the stars.

By comparison with these stars, they found that the star that became the magnetar must have been at least 40 times the mass of the Sun. This proves for the first time that magnetars can evolve from stars so massive we would normally expect them to form black holes. The previous assumption was that stars with initial masses between about 10 and 25 solar masses would form neutron stars and those above 25 solar masses would produce black holes.

"These stars must get rid of more than nine tenths of their mass before exploding as a supernova, or they would otherwise have created a black hole instead," says co-author Ignacio Negueruela. "Such huge mass losses before the explosion present great challenges to current theories of stellar evolution."

"This therefore raises the thorny question of just how massive a star has to be to collapse to form a black hole if stars over 40 times as heavy as our Sun cannot manage this feat," concludes co-author Norbert Langer.

The formation mechanism preferred by the astronomers postulates that the star that became the magnetar -- the progenitor -- was born with a stellar companion. As both stars evolved they would begin to interact, with energy derived from their orbital motion expended in ejecting the requisite huge quantities of mass from the progenitor star. While no such companion is currently visible at the site of the magnetar, this could be because the supernova that formed the magnetar caused the binary to break apart, ejecting both stars at high velocity from the cluster.

"If this is the case it suggests that binary systems may play a key role in stellar evolution by driving mass loss -- the ultimate cosmic 'diet plan' for heavyweight stars, which shifts over 95% of their initial mass," concludes Clark.

Notes

[1] The open cluster Westerlund 1 was discovered in 1961 from Australia by Swedish astronomer Bengt Westerlund, who later moved from there to become ESO Director in Chile (1970-74). This cluster is behind a huge interstellar cloud of gas and dust, which blocks most of its visible light. The dimming factor is more than 100 000, and this is why it has taken so long to uncover the true nature of this particular cluster.

Westerlund 1 is a unique natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Milky Way live and die. From their observations, the astronomers conclude that this extreme cluster most probably contains no less than 100 000 times the mass of the Sun, and all of its stars are located within a region less than 6 light-years across. Westerlund 1 thus appears to be the most massive compact young cluster yet identified in the Milky Way galaxy.

All stars so far analysed in Westerlund 1 have masses at least 30-40 times that of the Sun. Because such stars have a rather short life -- astronomically speaking -- Westerlund 1 must be very young. The astronomers determine an age somewhere between 3.5 and 5 million years. So, Westerlund 1 is clearly a "newborn" cluster in our galaxy.

More information

The research will soon appear in the research journal Astronomy and Astrophysics ("A VLT/FLAMES survey for massive binaries in Westerlund 1: II. Dynamical constraints on magnetar progenitor masses from the eclipsing binary W13," by B. Ritchie et al.). The same team published a first study of this object in 2006 ("A Neutron Star with a Massive Progenitor in Westerlund 1," by M.P. Muno et al., Astrophysical Journal, 636, L41).

The team is composed of Ben Ritchie and Simon Clark (The Open University, UK), Ignacio Negueruela (Universidad de Alicante, Spain), and Norbert Langer (Universität Bonn, Germany, and Universiteit Utrecht, the Netherlands).

The astronomers used the FLAMES instrument on ESO's Very Large Telescope at Paranal, Chile to study the stars in the Westerlund 1 cluster.

Read More

Seeing a Stellar Explosion in 3D

Seeing a Stellar Explosion in 3D

  1:17:00 AM    Science Lover

---

Astronomers using ESO's Very Large Telescope have for the first time obtained a three-dimensional view of the distribution of the innermost material expelled by a recently exploded star. The original blast was not only powerful, according to the new results. It was also more concentrated in one particular direction. This is a strong indication that the supernova must have been very turbulent, supporting the most recent computer models.

This artist's impression of the material around a recently 
exploded star, known as Supernova 1987A (or SN 1987A), 
is based on observations which have for the first time revealed 
a three dimensional view of the distribution of the expelled
material. The observations were made by astronomers using 
ESO's Very Large Telescope. The original blast was not 
only powerful, according to the new results. It was also 
more concentrated in one particular direction. This is a 
strong indication that the supernova must have been very 
turbulent, supporting the most recent computer models. 
This image shows the different elements present in SN 
1987A: two outer rings, one inner ring and the deformed, 
innermost expelled material. (Credit: ESO/L. Calçada)

Unlike the Sun, which will die rather quietly, massive stars arriving at the end of their brief life explode as supernovae, hurling out a vast quantity of material. In this class, Supernova 1987A (SN 1987A) in the rather nearby Large Magellanic Cloud occupies a very special place. Seen in 1987, it was the first naked-eye supernova to be observed for 383 years, and because of its relative closeness, it has made it possible for astronomers to study the explosion of a massive star and its aftermath in more detail than ever before. It is thus no surprise that few events in modern astronomy have been met with such an enthusiastic response by scientists.

SN 1987A has been a bonanza for astrophysicists. It provided several notable observational 'firsts', like the detection of neutrinos from the collapsing inner stellar core triggering the explosion, the localisation on archival photographic plates of the star before it exploded, the signs of an asymmetric explosion, the direct observation of the radioactive elements produced during the blast, observation of the formation of dust in the supernova, as well as the detection of circumstellar and interstellar material.

New observations making use of a unique instrument, SINFONI [1], on ESO's Very Large Telescope (VLT) have provided even deeper knowledge of this amazing event, as astronomers have now been able to obtain the first-ever 3D reconstruction of the central parts of the exploding material.

This view shows that the explosion was stronger and faster in some directions than others, leading to an irregular shape with some parts stretching out further into space.

The first material to be ejected from the explosion travelled at an incredible 100 million km per hour, which is about a tenth of the speed of light or around 100 000 times faster than a passenger jet. Even at this breakneck speed it has taken 10 years to reach a previously existing ring of gas and dust puffed out from the dying star. The images also demonstrate that another wave of material is travelling ten times more slowly and is being heated by radioactive elements created in the explosion.

"We have established the velocity distribution of the inner ejecta of Supernova 1987A," says lead author Karina Kjær. "Just how a supernova explodes is not very well understood, but the way the star exploded is imprinted on this inner material. We can see that this material was not ejected symmetrically in all directions, but rather seems to have had a preferred direction. Besides, this direction is different to what was expected from the position of the ring."

Such asymmetric behaviour was predicted by some of the most recent computer models of supernovae, which found that large-scale instabilities take place during the explosion. The new observations are thus the first direct confirmation of such models.

SINFONI is the leading instrument of its kind, and only the level of detail it affords allowed the team to draw their conclusions. Advanced adaptive optics systems counteracted the blurring effects of the Earth's atmosphere while a technique called integral field spectroscopy allowed the astronomers to study several parts of the supernova's chaotic core simultaneously, leading to the build-up of the 3D image.

"Integral field spectroscopy is a special technique where for each pixel we get information about the nature and velocity of the gas," says Kjær. "This means that besides the normal picture we also have the velocity along the line of sight. Because we know the time that has passed since the explosion, and because the material is moving outwards freely, we can convert this velocity into a distance. This gives us a picture of the inner ejecta as seen straight on and from the side."

Note: [1] The team used the SINFONI (Spectrograph for INtegral Field Observations in the Near Infrared) instrument mounted on ESO's Very Large Telescope (VLT). SINFONI is a near-infrared (1.1-2.45 µm) integral field spectrograph fed by an adaptive optics module.

Read More

The history of the universe – in 3D!

The history of the universe – in 3D!

  12:54:00 AM    Science Lover

---

In an international project, astronomers have obtained exceptional 3D images of distant galaxies, seen when the Universe was half its current age. And by looking at this unique “history book” of the universe, at an epoch when the Sun and the Earth did not even exist, scientists hope to solve the puzzle of how galaxies formed in the remote past.

The team – consisting of scientists from the US’ NASA, the European Space Agency and the European Southern Observatory – obtained the images by combining the Hubble Space Telescope’s acute eye with the capacity of the Very Large Telescope (VLT) to probe the motions of gas in tiny objects.

“Hubble and VLT are real ‘time machines’ for probing the universe’s history,” said Sébastien Peirani, lead author of one of the papers reporting on this study.

DOUBLING UP

For decades, distant galaxies that emitted their light six to eight billion years ago – over half the age of the universe – were no more than small specks of light on the sky.

With the launch of the Hubble Space Telescope in the early 1990s, astronomers were able to scrutinise the structure of these galaxies in some detail for the first time.

Now, researchers are using the Hubble’s capabilities in conjunction with those of the VLT – an array of four separate optical telescopes, situated at the Paranal Observatory in northern Chile. Its Fibre Large Array Multi Element Spectrograph (FLAMES) can observe up to 130 targets at a time, which enabled the team to measure the velocity of the gas in the distant galaxies.

“By seeing how the gas is moving, it provides us with a 3D view of galaxies halfway across the universe,” said François Hammer, who led the project.

The team is now reconstituting the history of about 100 remote galaxies. The project has already provided useful insights for three such galaxies.

UNRAVELLING GALACTIC SECRETS

In one galaxy, FLAMES revealed a region full of ionised gas – hot gas composed of atoms that have been stripped of one or several electrons. This is normally due to the presence of very hot, young stars.

However, even after staring at the region for more than 11 days, Hubble did not detect any stars! “Clearly, this unusual galaxy has some hidden secrets,” researcher Mathieu Puech said.

Computer simulations suggested that the explanation lies in the collision of two very gas-rich spiral galaxies. The heat produced by the collision would ionise the gas, making it too hot for stars to form.

Another galaxy that the scientists studied showed the opposite effect. There, they discovered a bluish central region enshrouded in a reddish disc, almost completely hidden by dust.

“The models indicate that gas and stars could be spiralling inwards rapidly,” said Hammer. “This might be the first example of a disc rebuilt after a major merger.”

Finally, in a third galaxy, the team saw a rare sight: an extremely blue, elongated structure – a bar, in fact – composed of young, massive stars. Comparisons with computer simulations showed that the properties of this object are well reproduced by a collision between two galaxies of unequal mass.

“The combination of Hubble and the VLT, along with modern computer simulations, allows us to model distant galaxies almost as nicely as the close ones,” Hammer said.

The team is now extending its analyses to the whole sample of galaxies observed.

“The next step will then be to compare this with closer galaxies, and so, piece together a picture of the evolution of galaxies over half the age of the universe,” he concluded.

If you like this post, buy me a beer at $3!

Read More