Questions related to Astrophysics
Quasars are believed to be objects ejected from the centers of the Galaxies (or Black holes). Do all of them blow outwards in opposite direction to us in order to agree all of them with such high redshifts ? Note that the motion of galaxies is random! While, even no one Quasar exhibits a blueshift !. Moreover, according to their high redshift all of the Quasars are very distant away. But the universe is isotropic, so our position is not preferred. Hence why we didn`t obsreve any Quasar nearby? According to the isotropy, a distant observer should observe the Quasars very distant with respect to him, that is they should be nearby to us!. Contradiction. According to Hubble`s law, if the object is bright then its near by and the distant objects are faint. The Quasars are very bright, why shouldn`t they nearby? Why we just accept one part from Hubble`s law, that is: the high redshift of the Quasar indicates that its distant and ignored the other part, that is: the brightness of the Quasar indicates they are nearby?!!1. Finally, Why our Galaxy and many other nearby Galaxies didn`t eject Quasars from their centers? Why this jop is exclusive for distant Galaxies? Because our Galaxy and many other nearby Galaxies are inactive, said astronomers. Why they are the inactiv among the active distant Galaxies? False justificatioin.It is clear such Paradigm is not satisfactory and insufficient, it depends on many unjustified reasons , many contradictions and inconsistent. The paradigm must be reconsidered and readjusted
I am interested in parametric resonance. An introduction to this phenomenon can be found in Landau's book on classical mechanics. Can anyone point out some good reviews on the phenomenon beyond the textbook level? I am looking for some applications of this phenomenon in astrophysical systems. Any suggestions in this direction are welcome
Estimate the ratio between the temperature scale height h = T(dT/dr)-1 and the mean free path of a hydrogen atom in the atmosphere of a star. Is local thermodynamic equilibrium a valid assumption in the stellar atmosphere? Where does it break down?
Its basic ingredients are fields : The Standard Model includes a field for each
type of elementary particle; These particles exhibit a wide variety of masses
that follow no recognizable pattern; The Standard Model has no mechanism that would account for any of these masses, unless we supplement it by adding additional fields, of a type known as scalar fields. The word “scalar” means that these fields do not carry a sense of direction, unlike the electric and magnetic fields and the other fields of the Standard Model.
To complete the Standard Model, we need to confirm the existence of these scalar fields and find out how many types there are? This is a matter of discovering new elementary particles, often called Higgs particles(why ?), that can be recognized as the quanta of these fields.
A massive O star has a typical luminosity of 3 x 1039 ergs s-1, a lifetime of 3 x 106 yr, a stellar-wind velocity of 5000 km s-1, and a mass- loss rate of 10-5 Ms yr-1. When it ends up as a supernova, ~5 Ms is ejected with a velocity of 5000 km s-1. How can estimate the contribution of these processes to the energy and the momentum of the ISM?
(I already solved the problem by setting the keyboard to US English, I explain a message below)
I'm trying to use SpekCalc to simulate a X ray tube, but apprently it's not showing the bremsstrahlung radiation. I´m using a peak energy of 100keV, a theta of 16 degrees, and 5 milimeters of aluminium. But I obtain the same results whatever I have tried. I'm runing release 1.1 light for macOS, and I obtained the same results for windows.
Note: I'm using the values Nf=2 and p=1, instead of those suggested by Poludniowski because apparently the GUI is not accepting any value minor than 1.0. I have been trying other values with similar results.
Cosmic Microwave Background Radiation (CMB). (question edit March 29, 2016)
Assume very dense proto-stellar formation prior to a cosmic inflation event as hypothesized in The Pearlman SPIRAL cosmological redshift hypothesis and no ongoing cosmic expansion subsequent to that cosmic inflation event.
Could the cause of the CMB be from:
Prior to the stellar formation?
During stellar formation?
Post stellar formation?
Prior to that cosmic inflation event?
during that event?
at the very end of that event?
Under The Standard Cosmology Model (SCM) the current distance to the most distant visible galaxies is 46.5 B LY. Is that understanding correct?
A sub-hypothesize in SPIRAL is the CMB should 'leak' have dissipated 1 LY per year radius beyond the most distant galaxy.
If valid under SCM the CMB is spread out over an area of a sphere with a radius of at least 59.99 B LY = 46.5B + 13.4B is this already established or a published hypothesis?
If CMB does not 'leak' / spread beyond the most distant stars at 1 LY per year why not?
Thank you in advance for any and all proposed solutions you can think of. r
Can we speak of a slight linear increase of the core density of sun-like stars during their stay in the main sequence ? As this is a period where gravitational effects are steadily balanced by the radiative pressure resulting from the progressive conversion of H into He. And the same with a bigger slope for the further period of conversion of He into C ?
Suppose the object belongs to high-soft regime as well as mechanically powerful (cavities, shock) and also has bright nucleus what does it indicate?
Is the anisotropic pressure can destroy the spherical symmetry of
the space-time? Can we use Anisotropic pressure for a spherically symmetric star?
According to Kippenhahn's diagram, there is a decrease, but it is not clear whether this decrease has the general shape of a negative exponential or a power law or is linear or whatever else. Could the shape be different in function of the star mass, eg. 10 - 30 times the solar mass compared to 1 - 3 times the solar mass ?
In the light that we get from stars we discern certain lines belonging to the most abundant elements in those stars. Assume that we would pass the light from a star through a prism in order to disperse the spectrum, then isolate the hydrogen line(s).
Which one of the hydrogen lines is the most abundant in stars? And what are its properties: is the light in that line coherent light, or is it thermal light? Is it polarized?
Hi, I am trying to find out the formula to calculate the precision of differential photometry. IRAF or SExtractor can give magnitude errors, but these errors are usually given as instrumental errors, therefore ignoring the errors introduced by the different extinction behaviors of comparison star of unknown spectral type. The possible intrinsic variation of the comparison star is usually not addressed. Besides, bias frame and dark current and flat field calibration error also exists. However, there is still not a unified formula to calculate these potential error for the time being. I've been puzzled by above problems and would greatly appreciate your comments and suggestions.
What I mean by this question is as follows:
We know that the growth/rise phase of solar flare components (Soft X-rays, Hard X-rays) is always associated with the solar radio type III burst and conconcurrent radio flux density. According to some space scientists and also we can see clearly, the type III burst extended over longer solar longitude, which is often consistent with the decay phase of the low energy (Soft X-ray of longer wavelength) flare component, indicating that it goes up to several thousands of kilometers in the IP medium. However, the radiated energy emitted from the decay phase is distributed over a long time indicating that the energy by shock wave perhaps is much more than the energy distributed by the decay phase of the solar flare component. To overcome the confusion on whether flare decay phase or shock wave is dominant in the interplanetary medium, it is important to determine the speed of the decay phase of the Soft X-ray components. I am looking for suggestion on this particular issue to determine the speed of the soft X-ray flux intensity (w/m^2).
Wormholes, within the theory of General Relativity, are microscopic and short lived, but many serious physicists have speculated openly and hoped that perhaps with negative energy (as yet undiscovered) they could be enlarged and held open longer. Kip Thorne is one of the leading names proposing such ideas. https://en.wikipedia.org/wiki/Kip_Thorne
However, astrophysicists have observed space to be essentially a flat Euclidean geometry at large scales https://en.wikipedia.org/wiki/Wilkinson_Microwave_Anisotropy_Probe . Inflation cosmology has been invoked to explain this (as well as uniformity) https://en.wikipedia.org/wiki/Inflation_(cosmology).
My question is, if space is Euclidean flat, does or does not that imply wormhole paths between two points would be longer than paths through ordinary space? I want to rule out time dilation paths, because these are already known from special relativity and are very short for the traveler, but the traveler cannot get back to the time point she started from. (Thorne suggests we could even get back to earlier time points with wormholes but I don't want to go there in this thread as there is no end to it). I am looking for space-like paths only that would take less time at velocities below the speed of light than paths through flat Euclidean space. Please, also no arguments about whether flat space conclusion is correct. This question is restricted to "what if the flat space conclusion is correct, then do wormholes, if ever practical, have a practical use for space travel."
In a recent paper, Yu-Gang Ma reports detection of antihelium-4 by RHIC-STAR team. Considering that our solar system is also composed of helium and hydrogen, then would propose a hypothesize that antimatter form of hydrogen and helium can also be detected in our solar system?
So what do you think? Is it possible to detect antihydrogen and antihelium in our solar system? If such detection is confirmed, then we will face a challenge to formulate a matter-antimatter model of solar system.
Consider a star with a static magnetic field (a magnetic Ap star, for example). Outside the star there is vacuum, the field there a potential field curl(B) = 0. Some force-free field is constructed in the interior of the star. The normal component Bn of this force-free field is evaluated on the surface of the star. This used as boundary condition to construct the field outside the star, using standard potential field theory. What's wrong with such a model for Ap stars; why is it not a counterexample to the vanishing force-free field theorem?
Suppose one part in 108 of the Sun’s luminosity is absorbed or isotropically scattered by grains circling the Sun. What is the total mass of such matter falling into the Sun each second?
A disk-shaped rotating galaxy is seen edge on. By Doppler-shift spectroscopic measurements we can determine the speed V with which the stars near the edge of the galaxy rotate about its center.How can show that the mass (M) of the galaxy is in terms of the observed velocity?
I am searching for spectra defined at least between 300 and 1100 nm with different temperatures, that are:
Where can i find them?
The observed Lithium abundance is in disagreement with the standard big bang model. What are the possible solutions to the problem? How much the observations are reliable in this case? Is it possible to exist a method of destruction of Li that we don't considering or it is beyond standard model phenomenon?
Domain walls or boundaries are expected to form when a discrete symmetry is broken spontaneously.
Y. B. Zeldovich, I. Y. Kobzarev and L. B. Okun, Zh. Eksp. Teor. Fiz. 67 (1974) 3
[Sov. Phys. JETP 40 (1974) 1]; T. W. B. Kibble, J. Phys. A9, 1387 (1976); A. Vilenkin, Phys. Rept. 121 (1985) 263
I am thinking of typical Mercury and Gemini retrofire maneuvers. Mercury was nose down about 34 degrees at retrofire. Gemini was about 20 degrees nose down. Is there a convenient way for a non-mathematician to estimate the resulting orbit after such a maneuver--maybe a graph or a macro or app?
As some of the research papers suggest that low FIP (below 10 KeV) elements get enhance by factor of 3-4 in Corona from Photosphere, while high FIP (above 10 KeV) elements don't show this characteristics.
Does this effect conclude anything about energy transfer from Photospere to Corona ?
Is it possible to source a URL or database of the available antennas in the field of millimeter and submillimeter astronomy?
I need to be able to tabulate available frequency-dependent beamsizes and antenna efficiencies.
The quantum field theoretic prediction for the vacuum energy density leads to a value for the effective cosmological constant that is incorrect by between 60 to 120 orders of magnitude. In a paper, George Ellis et al. (2010) review an old proposal of replacing Einstein's Field Equations by their trace-free part (the Trace-Free Einstein Equations), together with an independent assumption of energy--momentum conservation by matter fields. While this does not solve the fundamental issue of why the cosmological constant has the value that is observed cosmologically, it is indeed a viable theory that resolves the problem of the discrepancy between the vacuum energy density and the observed value of the cosmological constant. Therefore they confirm that no problems arise in such a scheme: hence, the Trace-Free Einstein Equations are indeed viable for cosmological and astrophysical applications.
So what do you think? Can the Trace-Free Einstein Equations be a Viable Alternative to General Relativity? Your comments are welcome
Warp field generation using metamaterials and sub-nanoscale casimir cavities architecture (e.g. optimising multiscallar geometry of warp propultion).
If neutrino travels through higher dimension than it may be possible that without travelling faster than light it can cover same distance as covered by light but in less time if light travels in 4 dimension
It would be helpful if the explanations are given for 3 categories:
1. Beginners using GUI
2. Wannabes using both GUI and TUI
3. Experts using TUI
The central densities that are adopted for the initial, cold, WDs in this paper, seem to be a lot lower than those quoted in most papers on the stability of WDs near the Chandrasekhar limit. These say that non-rotating WDs become unstable at 1.39Msun but at densities of 2-3E13 kg/m^3, which seems to be an order of magnitude greater than adopted in the initial configurations here. Is there a simple explanation for this? Neglect of GR?
In PNAS, August 25, 2009 edition, Blake and Smoller argued that perhaps the standard terminologies of dark energy and cosmological constant are not required for explaining the accelerated expansion of galaxies. According to them, the key to solve that puzzle is to find expanding wave solutions of the Einstein's equations.
So do you think it is possible to use expanding wave solutions of the Einstein's equations to solve accelerated expansion of galaxies? Your comments are welcome.
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.
I plan to conduct a research on Tardigrada survival in simulated Europa (moon) conditions. The question is:
If results will end up being significant - wouldn't it indirectly support the hypothesis of life existence possibility on Europa (in sum with results and analysis from Voyager & Galileo missions (R. Greenberg et al.)?
Long back perception on gravity was changed from a kind of force to a phenomenon which actually bends space- time in its influence. Is there any chance that even magnetism and electric forces and in fact all 4 types of forces can also be interpreted as such?
According to the authors, the regression method proposed by them takes into account the intrinsic scatter and errors in both variables. I have heard that this method does not rely on the Chi-square minimization but then how does one calculate whether his or her fit is good or not. Can I use this method to fit a model? if yes ,how do I conclude if my model fits the data correctly or not ?
By empty space I mean interstellar space.
I have read en.wikipedia.org/wiki/Neutron#Production_and_sources - I am not asking about those processes.
I remember reading about this years ago but can now find no reference to this process. I have forgotten the rate, something like 1 neutron per 1 cubic km per year or per century. The process may have been stated as the "decay" of empty space to produce a neutron.
I have seen different estimations of photon diffusion time in different papers (30000 to a million years). There are many different mean free paths used. I want to know if these results are just speculations or if there is a way to verify these results?
I also want to know what the current standard time of diffusion is. It would be helpful if you could give me the links to some important research papers on this subject.
Spacetime curvature creates a space time "seeing" effect, which is analogous to astronomical seeing. This is due to microlensing and weak lensing, which becomes problematic from an ICRF stability viewpoint as astrometric VLBI and optical measurements (e.g. GAIA) moves into the tens of micro-arcsecond accuracy region. This space time seeing effect will create a noise floor, limiting ICRF stability due to apparent source position distortions and amplitude variations. This will of course have an impact on the high accuracy requirements of the Global Geodetic Observing System (GGOS), which has the objectives of 0.1 mm stability and accuracy of 1 mm for the ITRF. The distribution of dark matter complicates the problem.
It is said that tensor perturbations in FRW metric satisfies some wave equations. And the solutions of those wave equations are called gravity waves. My confusion is why the word "gravity" comes into picture. Also scalar perturbations satisfy a wave equations. Why scalar perturbation are not called gravity waves?
Parks et al.  found the entropy of electrons are increased across the Earth's bow shock. Based on the Vlasov equation or the entropy conservation equation, the entropy of electrons are almost unchanged if their distribution is symmetrical (e.g. Maxwellian, flat-top etc.). What are your views on this?
What happens to a simple hydrogen atom, i.e. what happens to the energy binding between the electron and the proton, from the point of view of QED, when the hydrogen atom is close to a black hole?
Light experiences a redshift (blueshift) if it passes through a strong static gravitational field, as demonstrated by Einstein. Owing to gravity-electrostatic analogy, why does light not have the same effect if it passes through a static electric field?
See http://www.nature.com/news/cosmic-mismatch-hints-at-the-existence-of-a-sterile-neutrino-1.14752. It states:
"… The background radiation shows the small density variations in the early universe that would eventually cause matter to clump in some places and form voids in others. We can see the end product of this clumping in the recent universe by observing the spread of galaxy clusters across space.
"The best measurements of the cosmic background radiation came from the European Space Agency’s orbiting Planck telescope in March 2013. Galaxy-cluster measurements, on the other hand, come from various methods that include mapping the spread of mass across the universe by looking for the gravitational lensing, or warping of light, it causes. The two measurements, however, are inconsistent with one another. "We compare the universe at an early time to a later time, and we have a model that extrapolates between the two," says Richard Battye of the University of Manchester, UK, co-author of the new study1 published on 7 February in Physical Review Letters (PRL). "If you stick to the model that fits the CMB data, then number of clusters you find is a factor of two lower than you expect.""
Recent reports of X-ray signals that may signify the decay of sterile neutrinos have raised hopes for a cosmological solution, as some mix of Cold Dark Matter (CDM), Warm Dark Matter (WDM) and/or Hot Dark Matter (HDM) could fit CMB projections of galaxy cluster formations to observations since WDM and HDM would prevent structure formation at increasingly larger scales. See http://arxiv.org/abs/1308.3255 http://arxiv.org/abs/1402.2301 http://arxiv.org/abs/1402.4119 http://dx.doi.org/10.1103/PhysRevLett.112.051303 and http://dx.doi.org/10.1103/PhysRevLett.112.051302.
Also see http://phys.org/news/2014-02-massive-neutrinos-cosmological-conundrum.html https://www.technology.org/2014/02/25/neutrino-replaces-higgs-boson-sought-particle/ http://news.sciencemag.org/physics/2014/02/x-rays-other-galaxies-could-emanate-particles-dark-matter and http://www.nature.com/news/physics-broaden-the-search-for-dark-matter-1.14795.
However, if the composition of universal mass-energy included HDM or WDM and less total CDM than now thought, how would that affect the enormous gravitational effects routinely attributed to CDM in the observed universe?
Adding HDM and/or WDM may help with LCDM problems such as 'the small scale structure problem', 'the missing satellite problem', the 'cuspy halo problem' and others, but it must do so while maintaining alignment with other observations. What other L-CDM results would be affected by the inclusion of HDM and/or WDM?
What drives plate tectonics on Earth? Earth global forces (true polar wander, ridge push, slab pull) or forces connected to Earth axial rotation (tidal friction, eötvös effect), are usually invoked to describe the driving mechanisms of plate tectonics. Some of these forces provide the required energy to move plates (4x10^18 J/yr), but always with strong assumptions. Can the dark energy be considered/added with the previous ones? Is the dark energy sufficiently strong to affect the Earth dynamics? What are the best estimates of such energy?
Cosmological simulation predicts a large number of dwarf galaxies than the observed ones. This is known as missing satellite problem or dwarf galaxy problem. The interesting thing is that these satellite galaxies of Milky Way lie on a single plane.
When considering bending modes for linear polyatomic molecules containing hyperfine structure, how does increasing the vibrational state affect the various molecular parameters involved in calculating the hyperfine energy levels?
SN-1a data [Reiss et al., Perlmutter et al.] indicates that there is a deviation from a linear Hubble curve for data points at large distances, > 3-4 Gly. Theoretical fits are then made, based on Friedmann equations, that include a “dark energy” term, Lambda. From this fit it is shown that the rate of the expansion of the universe will lead to an accelerating universe. It is often stated that the universe is accelerating at the present time, T_0. But if one looks at the Hubble curve for only the past 2-3 billion years the Hubble curve can be fit nearly perfectly with a straight line. This indicates to me that there is no empirical evidence that the expansion of the universe is accelerating at the present time. In other words, the Lambda -fit curve _suggests_ that the expansion is accelerating at the present time but this acceleration is, in fact, presently _not_ observed to any degree of certainty over the past few billion years.
As far as I know, pulsar-based navigation has been intensively investigated. I wonder are there any other natural bodies in the universe that can emit stable signals like pulsars?
What will be the statistical properties of the error present in the signal?
It is of the order of 1 m^−3 (intergalactic medium) to 10^30 m^-3 (stellar core). My calculations show that it should be of the order of 10^23 m^-3. Is my order of magnitude alright?