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Extragalactic Astronomy - Science topic

Extragalactic astronomy is the branch of astronomy concerned with objects outside our own Milky Way Galaxy. In other words, it is the study of all astronomical objects which are not covered by galactic astronomy, the next level of galactic astronomy.
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Do you think that there is life beyond our Solar System?
Please, answer, comments.
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Extraterrestrial life is hypothetical life which may occur outside Earth and which did not originate on Earth. Such life might range from simple prokaryotes (or comparable life forms) to intelligent beings and even sapient beings, possibly bringing forth civilizations which might be far more advanced than humanity. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life in all its forms is known as astrobiology. https://en.m.wikipedia.org/wiki/Extraterrestrial_life
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Black Holes out of a galaxy: do they exist??? ➣➣The question is as follow.
Are there black holes outside the confines of a galaxy{*}, in the spaces between one galaxy and another??? 
{*}Galaxy is not meant only the Milky Way but any type of galaxy. In what way can be identified and/or measured these hypothetical extragalactic black holes???
➢➢Il quesito è il seguente. 
Esistono buchi neri al di fuori dei confini di una galassia{*}, negli spazi tra una galassia e l'altra??? 
{*}Galassia non viene intesa la sola Via Lattea ma qualsiasi tipo di galassia.
in che modo possono essere individuati e/o misurati questi ipotetici buchi neri extragalattici???
Previous POSTS:
►https://www.facebook.com/SalVi.SalvatoreVicidomini/posts/2378526012179048
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Is dark matter real, or have we misunderstood gravity? PHYS June 22 2021.
For many years now, astronomers and physicists have been in a conflict. Is the mysterious dark matter that we observe deep in the Universe real, or is what we see the result of subtle deviations from the laws of gravity as we know them? In 2016, Dutch physicist Erik Verlinde proposed a theory of the second kind: emergent gravity. New research, published in Astronomy & Astrophysics this week, pushes the limits of dark matter observations to the unknown outer regions of galaxies, and in doing so re-evaluates several dark matter models and alternative theories of gravity. Measurements of the gravity of 259,000 isolated galaxies show a very close relation between the contributions of dark matter and those of ordinary matter, as predicted in Verlinde's theory of emergent gravity and an alternative model called Modified Newtonian Dynamics. However, the results also appear to agree with a computer simulation of the Universe that assumes that dark matter is 'real stuff'.
The new research was carried out by an international team of astronomers, led by Margot Brouwer (RUG and UvA). Further important roles were played by Kyle Oman (RUG and Durham University) and Edwin Valentijn (RUG). In 2016, Brouwer also performed a first test of Verlinde's ideas; this time, Verlinde himself also joined the research team.
Matter or gravity?
So far, dark matter has never been observed directly—hence the name. What astronomers observe in the night sky are the consequences of matter that is potentially present: bending of starlight, stars that move faster than expected, and even effects on the motion of entire galaxies. Without a doubt all of these effects are caused by gravity, but the question is: are we truly observing additional gravity, caused by invisible matter, or are the laws of gravity themselves the thing that we haven't fully understood yet?
To answer this question, the new research uses a similar method to the one used in the original test in 2016. Brouwer and her colleagues make use of an ongoing series of photographic measurements that started ten years ago: the KiloDegree Survey (KiDS), performed using ESO's VLT Survey Telescope in Chile. In these observations one measures how starlight from far away galaxies is bent by gravity on its way to our telescopes. Whereas in 2016 the measurements of such 'lens effects' only covered an area of about 180 square degrees on the night sky, in the mean time this has been extended to about 1000 square degrees—allowing the researchers to measure the distribution of gravity in around a million different galaxies.
Comparative testing
Brouwer and her colleagues selected over 259,000 isolated galaxies, for which they were able to measure the so-called 'Radial Acceleration Relation' (RAR). This RAR compares the amount of gravity expected based on the visible matter in the galaxy, to the amount of gravity that is actually present—in other words: the result shows how much 'extra' gravity there is, in addition to that due to normal matter. Until now, the amount of extra gravity had only been determined in the outer regions of galaxies by observing the motions of stars, and in a region about five times larger by measuring the rotational velocity of cold gas. Using the lensing effects of gravity, the researchers were now able to determine the RAR at gravitational strengths which were one hundred times smaller, allowing them to penetrate much deeper into the regions far outside the individual galaxies.
This made it possible to measure the extra gravity extremely precisely—but is this gravity the result of invisible dark matter, or do we need to improve our understanding of gravity itself? Author Kyle Oman indicates that the assumption of 'real stuff' at least partially appears to work: "In our research, we compare the measurements to four different theoretical models: two that assume the existence of dark matter and form the base of computer simulations of our universe, and two that modify the laws of gravity—Erik Verlinde's model of emergent gravity and the so-called 'Modified Newtonian Dynamics' or MOND. One of the two dark matter simulations, MICE, makes predictions that match our measurements very nicely. It came as a surprise to us that the other simulation, BAHAMAS, led to very different predictions. That the predictions of the two models differed at all was already surprising, since the models are so similar. But moreover, we would have expected that if a difference would show up, BAHAMAS was going to perform best. BAHAMAS is a much more detailed model than MICE, approaching our current understanding of how galaxies form in a universe with dark matter much closer. Still, MICE performs better if we compare its predictions to our measurements. In the future, based on our findings, we want to further investigate what causes the differences between the simulations."
Young and old galaxies
Thus it seems that, at least one dark matter model does appear to work. However, the alternative models of gravity also predict the measured RAR. A standoff, it seems—so how do we find out which model is correct? Margot Brouwer, who led the research team, continues: "Based on our tests, our original conclusion was that the two alternative gravity models and MICE matched the observations reasonably well. However, the most exciting part was yet to come: because we had access to over 259,000 galaxies, we could divide them into several types—relatively young, blue spiral galaxies versus relatively old, red elliptical galaxies." Those two types of galaxies come about in very different ways: red elliptical galaxies form when different galaxies interact, for example when two blue spiral galaxies pass by each other closely, or even collide. As a result, the expectation within the particle theory of dark matter is that the ratio between regular and dark matter in the different types of galaxies can vary. Models such as Verlinde's theory and MOND on the other hand do not make use of dark matter particles, and therefore predict a fixed ratio between the expected and measured gravity in the two types of galaxies—that is, independent of their type. Brouwer: "We discovered that the RARs for the two types of galaxies differed significantly. That would be a strong hint towards the existence of dark matter as a particle."
However, there is a caveat: gas. Many galaxies are probably surrounded by a diffuse cloud of hot gas, which is very difficult to observe. If it were the case that there is hardly any gas around young blue spiral galaxies, but that old red elliptical galaxies live in a large cloud of gas—of roughly the same mass as the stars themselves—then that could explain the difference in the RAR between the two types. To reach a final judgement on the measured difference, one would therefore also need to measure the amounts of diffuse gas—and this is exactly what is not possible using the KiDS telescopes. Other measurements have been done for a small group of around one hundred galaxies, and these measurements indeed found more gas around elliptical galaxies, but it is still unclear how representative those measurements are for the 259,000 galaxies that were studied in the current research.
Dark matter for the win?
If it turns out that extra gas cannot explain the difference between the two types of galaxies, then the results of the measurements are easier to understand in terms of dark matter particles than in terms of alternative models of gravity. But even then, the matter is not settled yet. While the measured differences are hard to explain using MOND, Erik Verlinde still sees a way out for his own model. Verlinde: "My current model only applies to static, isolated, spherical galaxies, so it cannot be expected to distinguish the different types of galaxies. I view these results as a challenge and inspiration to develop an asymmetric, dynamical version of my theory, in which galaxies with a different shape and history can have a different amount of 'apparent dark matter'."
Therefore, even after the new measurements, the dispute between dark matter and alternative gravity theories is not settled yet. Still, the new results are a major step forward: if the measured difference in gravity between the two types of galaxies is correct, then the ultimate model, whichever one that is, will have to be precise enough to explain this difference. This means in particular that many existing models can be discarded, which considerably thins out the landscape of possible explanations. On top of that, the new research shows that systematic measurements of the hot gas around galaxies are necessary. Edwin Valentijn formulates is as follows: "As observational astronomers, we have reached the point where we are able to measure the extra gravity around galaxies more precisely than we can measure the amount of visible matter. The counterintuitive conclusion is that we must first measure the presence of ordinary matter in the form of hot gas around galaxies, before future telescopes such as Euclid can finally solve the mystery of dark matter."
More information: Margot M. Brouwer et al, The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000, Astronomy & Astrophysics (2021). DOI: 10.1051/0004-6361/202040108 ----- ABSTRACT. We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (gbar) with the observed gravitational acceleration (gobs), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in gobs into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between gobs and gbar agrees well with the MG predictions. In addition, we find a difference of at least 6σ between the RARs of early- and late-type galaxies (split by Sérsic index and u − r colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (Mgas ≈ M⋆) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.
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Will the new generation of astronomical instruments ever reach the farthest corners of the Universe, reach the edge of the universe and explain the essence of the boundlessness of what is possibly beyond the known Universe?
Perhaps someday in the future, thanks to the huge telescopes, we will discover the details of the distant planets in other planetary systems in other galaxies, i.e. exoplanets.
According to astronomers' forecasts, it will be technically possible to build such large telescopes in a few dozen years.
Astronomers have so far discovered a small part of the planets in our Andromeda Galaxy.
Billions of exoplanets existing in other constellations are still unknown.
However, even these known exoplanets are studied to a very limited extent.
In the case of the majority of exoplanets learned, apart from the knowledge of size and mass, little is known about them.
More and more perfect astronomical tools are being built, more and more telescopes provide new knowledge.
Thanks to more perfect astronomical instruments, we know more and more about the cosmos, but on the other hand we know that we still do not know more and more about the vastness of the Universe.
Will we ever know the answer to the question: Are there other forms of life somewhere in the Universe and how does life look like?
Will the new generation of astronomical instruments ever reach the farthest corners of the universe, reach the edge of the Universe and explain the essence of the boundlessness of what is possibly beyond the known Universe?
In view of the above, the current question is: Will the new generation of astronomical instruments ever reach the farthest corners of the Universe, reach the edge of the Universe and explain the essence of the boundlessness of what is possibly beyond the known Universe?
Please, answer, comments. I invite you to the discussion.
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Where no one has seen before
IEEE Spectrum January 2021 (attached) p. 30 - 31 (32-33)
The James Webb Space Telescope will let us see back almost to the big bang!!!
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In many cosmological theories, astronomers try to explain the essence of the unlimitedness of the Universe. But how can this unlimitedness be presented and defined in the most concise and clear way possible?
What can be compared to the unlimitedness of the Universe? Or maybe the essence of the problem goes beyond the scientific definition of the concept of the unlimitedness of the Universe?
The problem may be the understanding of this unlimitedness of the Universe by man, because everything that surrounds man in everyday life on Earth is limited.
Do you agree with my opinion on this matter?
In view of the above, I am asking you the following question:
How is the unlimitedness of the Universe explained now?
Please reply
I invite you to the discussion
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The concept of the finite universe or an universe limited in apace and time is due to the limitation of any epistemology based on causality for which there has to be a first cause of a beginning. Idealized mathematics promoted by the Platonists and the rationalists is the epitome of causality based epistemology and cosmology.
Albert Einstein adopted Platonic mathematical idealism in modern physics after the breakdown of causality with the discovery of the revolutionary quantum phenomena. But mathematics is helpless to deal with the concept of the Infinite as Cantor found out. Einstein’s theories of relativity, specially GR that is the basis of modern official cosmology, necessarily started with the presupposition that the universe must be finite; but this is a wishful thinking just for the convenience of his mathematical approach to epistemology and cosmology!
Einstein’s theories of relativity are invalid and have no place in an infinite universe. And the universe IS infinite! Please see the links below:
Recently, there has been calls in RG for medieval type Inquisition to deal with the growing number of scientists who doubt or even deny the validity of Einstein’s theories of relativity. The following forum is an example:
But the relativists, Crusaders and the Inquisitors of official physics in RG have now already been silenced through the power of logic and science alone:
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When are the first manned trips to Mars planned?
Considering technological development, when will it be possible to establish the first permanent research bases and residential colonies on Mars?
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I am not sure what to understand under term "colonize". Mars is a smaller planet than Earth, but it is still very huge object and pretty far away - and our present technology has difficulties even to land there by robots (though NASA is the best). So far there is no achievement to send a robotic probe that would be able to land there and return back to Earth... And we are ready to discuss about the colonization. What about "colonization", let's say, 10% of Sahara? We have lot of people for manpower, food, water supply, health care, good air to breathe, million tons of heavy construction equipment... If you mean to make "Mars habitable for humans" I am very skeptic, mother Nature is much-much stronger (will we make breathable atmosphere ? will we make artificial magnetic field to protect atmosphere against solar wind erosion?, etc...) Mars - perhaps for robots... For humans, top task is to save the Earth...
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The pictures of 'I Zwicky 18' showing remarkable similarities to pictures of supernovas thousand of years after explosion. Probable happened in the centre of Zwicky a gigantic explosion. The gravitational centre disappeared almost totally. Many new stars are formed currently from matter and energy(!). The former galaxy is now in a disordered state. The widely known shape of galaxies will be rebuilt by and by.
The increasing concentration of stars respectively matter in the centres of galaxies leads at intervals of several ten million years to explosions. (See also the periodical extinctions of life on earth.) We have to assume a gigantic energetic-material cycle in universe. In case of 'Zwicky' the usual (energetical) explosion got out of control.
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Dear Thierry!
You are right insofar, that every galaxy has an anisotropic gravitational field. It is caused by the mass distribution evoked by rotation movement. Only in a very high distance you can calculate with a single (or simple) mass centre.
A star cluster, which arised par example in the peripery will be deformed by different rotation speeds, gravity and delay. It leads to the spiral shape. (The delay is an issue of a paper I am working on.)
My point is that galaxies are going through a cyclic development. We can observe different states of this development respectively the different states of activity.
@M. Cerviño: I am astonishing about the pictures of early galaxies maybe before 12billion years. They show the same shape as current galaxies. Is this not a contradiction to the big bang theory?
Hans
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Suppose the object belongs to high-soft regime as well as mechanically powerful (cavities, shock) and also has bright nucleus what does it indicate?
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Please read the paper, may be helpful for you.  A new approach to the correction of
Galilean transformation.
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Tell me please who is researching the atmospheres of exoplanets, and the most of circulation?
For who conducted this research?
Does the existence of a developed theory of atmospheres on exoplanets depending on different astronomical conditions?
What organizations are engaged?
Where can I read about it?
Dolia Vadym.
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Indeed, the energy coming from the parent star controls the composition, the temperature and the circulation of the atmosphere, which are in fact coupled. To study the circulation in exoplanet atmospheres, you can use a GCM-type model (Global Climate Model). You will find useful references in the paper quoted above. 
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In the degenerate interiors of neutron stars, the equation of state is usually just density (and composition) dependent. You can express the pressure as a polytropic law of the form P∝ρα, where ρ is the density.
A stiff (or hard) equation of state is one where the pressure increases a lot for a given increase in density. Such a material would be harder to compress and offers more support against gravity. Conversely, a soft equation of state produces a smaller increase of pressure for a change in density and is easy to compress.
If we using the Lagrangian density of the nucleon-meson many body system. Solve the equation of state and corresponding using different parameters like FSUGOLD,NL3,NL3*.....etc. I know every parameters have a different symmetry energy and compressibility.  But, what is physics behind the stiff or soft equation of state?
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I should probably start by saying that the very Physics behind the occurrence of the "stiff" and "soft" equations of state is quite complicated. You can subdivide the EOS into regions: I. Nuclear saturation density; II. Supra-saturation nuclear density. Now for each case the stiffness/softness comes from two main ingredients: (a) EOS of symmetric nuclear matter; (b) EOS of pure neutron matter --> this one can be replaced by the nuclear symmetry energy. Now we can talk about the Physics behind the stiffness/softness for each case:
I. (a) The stiffness/softness is mostly controlled by the incompressibility parameter that can be more or less constrained by nuclear breathing modes. There are no big variations (for example it is well constrained to be about 200 < K < 260 MeV)
I. (b) The stiffness/softness is due variation of the nuclear symmetry energy. The large uncertainty comes from our poor knowledge on isovector channel of nuclear interaction. Physics of exotic nuclei close to dripline contain this information, however they are not yet readily available. This is a hot topic of research.
II. (a) The stiffness/softness is controlled by the skewness parameter (third derivative of energy per nucleon). The physics of finite nuclei is not sensitive to this variation, and therefore one can have models giving ranges of the EOS with maximum NS mass from 2 to 3 solar masses.
II. (b) Density dependence of the symmetry energy at suprasaturation is basically unknown. That is why we have a huge variations in the EOSs. 
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It is scientifically desirable to include stellar scale dark matter candidates, such as stellar-mass and planetary-mass ultracompact objects, in discussions of the quest for the identity of the enigmatic dark matter comprising the overwhelming majority of matter in the cosmos.
After 40 years of failed attempts to find the ad hoc "WIMPs", or any other form of subatomic dark matter particles, maybe it is time to completely reassess what the dark matter might be.
Mike Hawkins has offered a cogent empirically-supported case for stellar-mass and planetary-mass ultracompacts (with primordial black holes being the most likely candidates) as the mystery objects causing microlensing events seen in bulge, halo and QSO research. [papers available for free: http://arxiv.org/abs/1106.3875 and  http://arxiv.org/abs/1503.01935 ].
A huge population of primordial black holes satisfies the non-baryonic constraint, might also explain where cosmic rays primarily come from, and might explain why the ARCADE-2 experiment found a unexplained factor-of-6 excess in cosmological radio emission. Primordial black holes also might constitute the sources of the approximately 6,000/day Fast Radio Bursts that have been discovered/inferred in the last few years by several astrophysical research groups (Science News, Aug. 9, 2014 issue; many papers subsequently posted to arxiv.org). 
It is a scientific error to assume, as most theoretical physicists do, that the dark matter absolutely must be composed of hypothetical subatomic particles. A scientist maintains an open mind, in word and deed. Moreover, a scientist does not condone denial of important and confirmed empirical results.
Not long ago microlensing research (MOA group) identified at least 0.1 trillion unbound planetary-mass objects in unknown physical states (Suni et al, Nature, May, 2011).
Astrophysicists have discovered an estimated 70 billion brown dwarf objects in the thin disk of the Galaxy. Since the thin disk represents a very small fraction of the Galaxy's volume, one can be reasonably sure that 70,000,000,000 is a lower limit.
So let's see: trillions of unbound planetary-mass nomads and >70 billion brown dwarfs and 100s of billions of stellar-mass MACHO objects. That's a significant percentage of the total dark matter population, and it is a minimum estimate!
Can we understand why theoretical physicists and the scientific press ignore observed stellar scale dark matter candidates, and only emphasize mythical particles like WIMPs and axions that have never been observed? It seems like a dubious and unscientific obsession.
R.L. Oldershaw
Discrete Scale Relativity/Fractal Cosmology
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Let me add, it is true that planets and compact stars contribute to what could be called dark baryons and we do search for them. But they cannot make up for most of the dark matter, as structure formation as we understand it today would not work out.
Primordial black holes are excellent candidates for DM and we do search for them.
I agree with you that in the press WIMPs and maybe axions get most of the attention, but there is also a good reason for it, we have a clear experimental programme on how to either find them or to improve our limits. And we have non-cosmological reasons to postulate the existance of such particels (as e.g. in the case of axions). For PBHs there are vast regions of parameter space in which no currently known experimental method would allow us to identify them and we do not have a compelling production mechanism. Nevertheless they are not excluded. We do what we can do!
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I am an observational astrophysicist. From my perspective, the type Ia supernovae are the most important and clear evidence for the present accelerated phase of the universe. However I read a theoretical paper arguing that the very small anisotropies found in the CMB are also evidence for the accelerated expansion. How come? What is the realation?
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The discovery of the accelerating expansion of the Universe is a milestone for
cosmology, as significant as the discovery of the minute temperature variations in the
Cosmic Microwave Background (CMB) radiation with the COBE satellite (Nobel Prize
in Physics 2006, John Mather and George Smoot). By studying the CMB, we may learn
about the early history of the Universe and the origins of structure, whereas the
expansion history of the Universe gives us insights into its evolution and possibly its
ultimate fate.
The expansion of the Universe was discovered by Vesto Slipher, Carl Wirtz, Knut
Lundmark, Georges Lemaître and Edwin Hubble in the 1920’s. The expansion rate
depends on the energy content – a Universe containing only matter should eventually
slow down due to the attractive force of gravity. However, observations of type Ia
supernovae (SNe) at distances of about 6 billion light years by two independent research
groups, led by Saul Perlmutter and by Brian Schmidt and Adam Riess respectively,
reveal that presently the expansion rate instead is accelerating.
Within the framework of the standard cosmological model, the acceleration is generally
believed to be caused by the vacuum energy (sometimes called ”dark energy”) which –
based on concordant data from the SNe, the observations of the anisotropies in the CMB
and surveys of the clustering of galaxies – accounts for about 73% of the total energy
density of the Universe. Of the remainder, about 23% is due to an unknown form of
matter (called ”dark matter”). Only about 4% of the energy density corresponds to
ordinary matter like atoms.
In everyday life, the effects of the vacuum energy are tiny but measurable – observed
for instance in the form of shifts of the energy levels of the hydrogen atom, the Lamb
shift (Nobel Prize in Physics 1955).
The evolution of the Universe is described by Einstein’s theory of general relativity. In
relativistic field theories, the vacuum energy contribution is given by an expression
mathematically similar to the famous cosmological constant in Einstein’s theory. The
question of whether the vacuum energy term is truly time independent like the
cosmological constant, or varies with time, is currently a very hot research topic.
source:THE aCCELERATING UNIVERSE
compiled by the Class for Physics of the Royal Swedish Academy of Sciences
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The Javalambre-PAU Astrophysical Survey has just published is red book providing all the technical and scientific details about it. The main characteristic of the J-PAS project is its used of a particular set of narrow band optical filters (54) to compute photometric redshifts for millions of galaxies spread along more than 8500deg².
As a J-PAS member, I'd like to know your opinions about this technique and about the J-PAS survey in general.
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Hi Somak,
  as far as I know, there hasn't been work (within the collaboration) on specific spectral features since BPZ uses templates. I'd say that depending on the spectral type of the galaxies and their redshift, the most informative feature will change. Therefore, using templates avoid biases related with putting too much weight to specific features.
  With respect to previous multifilter surveys, like COMBO17, I would say that what made very powerful the J-PAS filter system is that the design of the filters has been done from scratch to maximize the photo-z determination (this is explained in Sect.2 of the document). The result is that the filters are narrow (145A), almost top hat with no wings, and there is no gaps between them, covering the whole optical range.
  For any further information about J-PAS, please don't hesitate to contact me or any member of the collaboration.
  Cheers!
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The ALHAMBRA survey (http://alhambrasurvey.com/) has just published its 1st full data release.
You can find the the data (catalogs with photo-z and synthetic F814W images) through the following links:
Enjoy!!
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Hi Somak,
  the description of the data in the catalogues can be found in Molino et al.(2014) paper:
  If you have doubts about the content of the catalogues, I would suggest to contact directly the first author (Dr. Alberto Molino).
  Regarding the public images, you are right, they are indeed the synthetic F814W images reconstructed from the narrow band images. The way in which they have been constructed is also explained in Molino et al.(2014).
  Finally, with respect to the NIR images, I'll try to find out whether they will be made public.
Cheers!
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Of the 72 central supermassive black holes on the McConnell and Ma table in their paper “Revisiting the Scaling Relations of Black Hole Masses and Host Galaxy Properties”, I have only found six galaxies in which the baryonic mass has been estimated for the entire galaxy. McConnell and Ma have listed the mass of 41 central bulges of these galaxies; however, in this project the central bulge is not a good proxy for total mass. In addition to publications, any leads to people who or institutions that may have done these calculations would be helpful.
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I also suggest a recent paper - http://arxiv.org/abs/1212.5317.
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Considering the revolution that occurred in terms of optical astrometry due to astrometric satellites such as Hipparcos (even though there were parallel developments and major improvements on ground-based astrometric telescopes), an even larger jump is about to occur with the GAIA astrometric mission. Much work will need to be done to tie the radio reference frame (ICRF2) to the GAIA optical reference frame. There will be ground-based follow-up work following GAIA detections, proper motions and parallax work, as satellite missions are relatively short lived and expensive. But, what does the future hold for ground-based astrometry? Near Earth objects? Solar system measurements? Reference frame maintenance?
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To complete a bit the excellent answers given before, once Gaia is finished, we will need to go on observing Solar System objects, even if the precision of the observations we obtain are lower than those of Gaia.
Gaia observations will not have an infinite precision, and will be biaised, like any instrument. Because of these errors and uncertainties, the accuracy of the ephemeris obtained will be limited in time. The positions obtained for the observation time-span will be very accurate, and will begin to degrade with time once we do not observe the bodies anymore. This is how some irregular satellites of Jupiter and some asteroids are now considered as lost: we haven't observed tham for a long time, and their real position is now far from the one given by the dynamical models used. In fact, for long-term accuracy, it is better to have a long time span with less precise observations, than a very short time span of precise observations.
So, for Solar System objects, Gaia will definitely not be the end of observations, but a much needed step toward mas/submas accurate ephemeris.
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Are the chemical reactions that take place on earth really influenced by gravity or are they affected by another planet or satellite around the earth?
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I would say that the gravity-dependence of chemical reactions can be neglected for two reasons:
1) the enthalpy has to be used with a little bit carefullnes in this context. The enthalpy is defined as the energ content of thermodynamical systems. However, this holds for every system, regardless of the occurence of a chemical reaction. If you want to study chemical reactions, you have to use the change of enthalpy dH. This is defined by: dH = TdS + V dp (T being the absolute temperature, dS the change of entropy and V the volume). If you work at constant pressure dp = 0. This is mostly the case, as you have no pressure variation for solids and nearly no variation in liquids or gases (as long as you are not dealing with very large volumes (i.e. some km³ or so).
and, even more important
2) all chemical reactions are driven by the electrons, or, more generally, by electric forces between charged particles. As the electric force between, say, an electron and a proton, is around forty! orders of magnitude stronger than their gravitational force, one can immediately see that gravitation is neglible compared to electrical forces.
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To describe how bright a star seems.
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Oh this was a fantastic answer Paul. I was trying to understand
this redshift for last few months but never had enough time to
dig into the literature.
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This morning ESA unveiled the first results from analysis of the the Planck Satellite data on the cosmic background. There are changes to values of certain of the important quantities that define our Universe. But no information as yet from polarization data.
Any reactions, ideas, ...
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Heleri,
Sorry I don't think I answered the question you asked which perhaps implied that the B-mode signal was non-Gaussian. It is Gaussian but not covered by the purely temperature angular power spectrum (TT) as they are part of the polarized fields which are E and B. These E and B distributions can also be described by spherical harmonics which are uncorrelated and random just like the temperature distribution and so are Gaussian.
The EE signal was seen by DASI several years ago, but is caused by the local temparature isotropy scattering differently into different linear polarizations when the Universe became transparent. Just to complicate matters this causes correlations between T and E due to this scattering process off electrons, which has also seen. This is still Gaussian
It's the handedness or parity of the gravitational waves which causes the special spiral B-mode pattern in polarization everyone is looking for.
Pulsar observers will tell they saw indirect evident of gravitational waves, but very indirect in my point of view. Seeing the run down rate of a fast binary pulsar orbit (PSR 1913+16) consistent with gravitation radiation emission rate via General Relativity.
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In some books popularizing science (e.g. “Astronomy for dummies” by S.P. Maran) it is written that black holes have the following structure: falling matter, event horizon, singularity. This structure does not coincide with the classification used in special literature where the accretion disk forming by falling matter is included. Is the black hole structure in the book above an adequate explanation for non-specialists?
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Yes, I understand now. Putting r=R, the criitcal value of C actually equals 2 radians, i.e. about 115 degrees.
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I am interested in your findings and opinions regarding the question.
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Try this - its old , but was pretty deep
but there are several more recent CCD based surveys as well
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I know that there are stars in a emission nebula, but in a reflection nebula?
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Examples are the reflection nebulae around the stars of the Pleiades.