Tag Archives: cosmos

Researchers use real data rather than theory to measure the cosmos

For the first time researchers have measured large distances in the Universe using data, rather than calculations related to general relativity.

A research team from Imperial College London and the University of Barcelona has used data from astronomical surveys to measure a standard distance that is central to our understanding of the expansion of the universe.

Previously the size of this ‘standard ruler’ has only been predicted from theoretical models that rely on general relativity to explain gravity at large scales. The new study is the first to measure it using observed data. A standard ruler is an object which consistently has the same physical size so that a comparison of its actual size to its size in the sky will provide a measurement of its distance to earth.

“Our research suggests that current methods for measuring distance in the Universe are more complicated than they need to be,” said Professor Alan Heavens from the Department of Physics, Imperial College London who led the study. “Traditionally in cosmology, general relativity plays a central role in most models and interpretations. We have demonstrated that current data are powerful enough to measure the geometry and expansion history of the Universe without relying on calculations relating to general relativity.

“We hope this more data-driven approach, combined with an ever increasing wealth of observational data, could provide more precise measurements that will be useful for future projects that are planning to answer major questions around the acceleration of the Universe and dark energy.”

The standard ruler measured in the research is the baryon acoustic oscillation scale. This is a pattern of a specific length which is imprinted in the clustering of matter created by small variations in density in the very early Universe (about 400,000 years after the Big Bang). The length of this pattern, which is the same today as it was then, is the baryon acoustic oscillation scale.

The team calculated the length to be 143 Megaparsecs (nearly 480 million light years) which is similar to accepted predictions for this distance from models based on general relativity.

Published in Physical Review Letters, the findings of the research suggest it is possible to measure cosmological distances independently from models that rely on general relativity.

Einstein’s theory of general relativity replaced Newton’s law to become the accepted explanation of how gravity behaves at large scales. Many important astrophysics models are based on general relativity, including those dealing with the expansion of the Universe and black holes. However some unresolved issues surround general relativity. These include its lack of reconciliation with the laws of quantum physics and the need for it to be extrapolated many orders of magnitude in scales in order to apply it in cosmological settings. No other physics law have been extrapolated that much without needing any adjustment, so its assumptions are still open to question.

Co-author of the study, Professor Raul Jimenez from the University of Barcelona said: “The uncertainties around general relativity have motivated us to develop methods to derive more direct measurements of the cosmos, rather than relying so heavily on inferences from models. For our study we only made some minimal theoretical assumptions such as the symmetry of the Universe and a smooth expansion history.”

Co-author Professor Licia Verde from the University of Barcelona added: “There is a big difference between measuring distance and inferring its value indirectly. Usually in cosmology we can only do the latter and this is one of these rare and precious cases where we can directly measure distance. Most statements in cosmology assume general relativity works and does so on extremely large scales, which means we are often extrapolating figures out of our comfort zone. So it is reassuring to discover that we can make strong and important statements without depending on general relativity and which match previous statements. It gives one confidence that the observations we have of the Universe, as strange and puzzling as they might be, are realistic and sound!”

The research used current data from astronomical surveys on the brightness of exploding stars (supernovae) and on the regular pattern in the clustering of matter (baryonic acoustic oscillations) to measure the size of this ‘standard ruler’. The matter that created this standard ruler formed about 400,000 years after the Big Bang. This period was a time when the physics of the Universe was still relatively simple so the researchers did not need to consider more ‘exotic’ concepts such as dark energy in their measurements.

“In this study we have used measurements that are very clean,” Professor Heavens explained, “And the theory that we do apply comes from a time relatively soon after the Big Bang when the physics was also clean. This means we have what we believe to be a precise method of measurement based on observations of the cosmos. Astrophysics is an incredibly active but changeable field and the support for the different models is liable to change. Even when models are abandoned, measurements of the cosmos will survive. If we can rely on direct measurements based on real observations rather than theoretical models then this is good news for cosmology and astrophysics.”

The research was supported by the Royal Society and the European Research Council.

Source : Imperial College

This artist's impression shows schematically the mysterious alignments between the spin axes of quasars and the large-scale structures that they inhabit that observations with ESO’s Very Large Telescope have revealed. These alignments are over billions of light-years and are the largest known in the Universe.

The large-scale structure is shown in blue and quasars are marked in white with the rotation axes of their black holes indicated with a line.

This picture is for illustration only and does not depict the real distribution of galaxies and quasars.

Credit:

ESO/M. Kornmesser

Spooky Alignment of Quasars Across Billions of Light-years

VLT reveals alignments between supermassive black hole axes and large-scale structure


New observations with ESO’s Very Large Telescope (VLT) in Chile have revealed alignments over the largest structures ever discovered in the Universe. A European research team has found that the rotation axes of the central supermassive black holes in a sample of quasars are parallel to each other over distances of billions of light-years. The team has also found that the rotation axes of these quasars tend to be aligned with the vast structures in the cosmic web in which they reside.

Quasars are galaxies with very active supermassive black holes at their centres. These black holes are surrounded by spinning discs of extremely hot material that is often spewed out in long jets along their axes of rotation. Quasars can shine more brightly than all the stars in the rest of their host galaxies put together.

This artist's impression shows schematically the mysterious alignments between the spin axes of quasars and the large-scale structures that they inhabit that observations with ESO’s Very Large Telescope have revealed. These alignments are over billions of light-years and are the largest known in the Universe. The large-scale structure is shown in blue and quasars are marked in white with the rotation axes of their black holes indicated with a line. This picture is for illustration only and does not depict the real distribution of galaxies and quasars. Credit: ESO/M. Kornmesser
This artist’s impression shows schematically the mysterious alignments between the spin axes of quasars and the large-scale structures that they inhabit that observations with ESO’s Very Large Telescope have revealed. These alignments are over billions of light-years and are the largest known in the Universe.
The large-scale structure is shown in blue and quasars are marked in white with the rotation axes of their black holes indicated with a line.
This picture is for illustration only and does not depict the real distribution of galaxies and quasars.
Credit:
ESO/M. Kornmesser

A team led by Damien Hutsemékers from the University of Liège in Belgium used the FORS instrument on the VLT to study 93 quasars that were known to form huge groupings spread over billions of light-years, seen at a time when the Universe was about one third of its current age.

The first odd thing we noticed was that some of the quasars’ rotation axes were aligned with each other — despite the fact that these quasars are separated by billions of light-years,” said Hutsemékers.

The team then went further and looked to see if the rotation axes were linked, not just to each other, but also to the structure of the Universe on large scales at that time.

When astronomers look at the distribution of galaxies on scales of billions of light-years they find that they are not evenly distributed. They form a cosmic web of filaments and clumps around huge voids where galaxies are scarce. This intriguing and beautiful arrangement of material is known as large-scale structure.

The new VLT results indicate that the rotation axes of the quasars tend to be parallel to the large-scale structures in which they find themselves. So, if the quasars are in a long filament then the spins of the central black holes will point along the filament. The researchers estimate that the probability that these alignments are simply the result of chance is less than 1%.

A correlation between the orientation of quasars and the structure they belong to is an important prediction of numerical models of evolution of our Universe. Our data provide the first observational confirmation of this effect, on scales much larger that what had been observed to date for normal galaxies,” adds Dominique Sluse of the Argelander-Institut für Astronomie in Bonn, Germany and University of Liège.

The team could not see the rotation axes or the jets of the quasars directly. Instead they measured the polarisation of the light from each quasar and, for 19 of them, found a significantly polarised signal. The direction of this polarisation, combined with other information, could be used to deduce the angle of the accretion disc and hence the direction of the spin axis of the quasar.

The alignments in the new data, on scales even bigger than current predictions from simulations, may be a hint that there is a missing ingredient in our current models of the cosmos,” concludes Dominique Sluse.

More information

This research was presented in a paper entitled “Alignment of quasar polarizations with large-scale structures“, by D. Hutsemékers et al., to appear in the journal Astronomy & Astrophysics on 19 November 2014.

The team is composed of D. Hutsemékers (Institut d’Astrophysique et de Géophysique, Université de Liège, Liège, Belgium), L. Braibant (Liège), V. Pelgrims (Liège) and D. Sluse (Argelander-Institut für Astronomie, Bonn, Germany; Liège).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Source: ESO


This artist’s impression depicts the formation of a galaxy cluster in the early Universe. The galaxies are vigorously forming new stars and interacting with each other. Such a scene closely resembles the Spiderweb Galaxy (formally known as MRC 1138-262) and its surroundings, which is one of the best-studied protoclusters.

Credit:

ESO/M. Kornmesser

Universe may face a darker future

Since the discovery of the accelerated expansion of the universe in 1997 by High-Z Supernova Team led by Prof. Brian Schmidt and Adam Rees, and by Supernova Cosmology Project Team led by Prof. Saul Perlmutter, the question of the nature of this expansion and the role of the mysterious dark energy has puzzled the minds of many theoretical and observational physicists/astrophysicists.

Another puzzling question in astronomy comes from the unusual behavior of the stars revolving around the galaxies with higher velocities than expected if we consider the apparent baryonic matter in the galaxy.This has led to many new questions related to something we called the dark matter, another unexplained phenomenon.

 


 

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

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

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

Professor David Wands, Director of Portsmouth’sInstitute of Cosmology and Gravitation, is one of the research team.

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

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

 

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

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

Research students Valentina Salvatelli and Najla Said from the University of Rome worked in Portsmouth with Dr Marco Bruni and Professor Wands, and with Professor Alessandro Melchiorri in Rome. They examined data from a number of astronomical surveys, including the Sloan Digital Sky Survey, and used the growth of structure revealed by these surveys to test different models of dark energy.

Professor Wands said: “Valentina and Najla spent several months here over the summer looking at the consequences of the latest observations. Much more data is available now than was available in 1998 and it appears that the standard model is no longer sufficient to describe all of the data. We think we’ve found a better model of dark energy.

“Since the late 1990s astronomers have been convinced that something is causing the expansion of our Universe to accelerate. The simplest explanation was that empty space – the vacuum – had an energy density that was a cosmological constant. However there is growing evidence that this simple model cannot explain the full range of astronomical data researchers now have access to; in particular the growth of cosmic structure, galaxies and clusters of galaxies, seems to be slower than expected.”

Professor Dragan Huterer,of the University of Michigan, has read the research and said scientists need to take notice of the findings.

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

Source: Materials taken from Uop News