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# Galaxy Evolution - Science topic

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Need weight of each component and their dimensions, also mass and velocity data of any of ion bombardment thrusters ( otherwise any other thruster data too is welcome )?
You can look at the literature for the material and dimension of such thruster and make a 3D geometry in software like Solidworks to get the exact data.
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Do you think that there is life beyond our Solar System?
I invite you to the discussion.
Best wishes
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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The greenhouse effect is gradually progressing on Earth. Consequently, the risk of new climate disasters increases every year.
Currently, technologies are being developed with the help of which space ships will be built to enable a manned space mission to Mars.
In the 21st century, will man be able to overcome greater distances and get to know some other planets of our solar system?
Is it possible to develop on Earth a technology that a man can leave the solar system and, for example, one day he can reach the nearest Alpha Centauri constellation?
In connection with the above, the question arises: Will man manage to create technologies thanks to which he will leave the planet Earth, the Solar System and reach other planetary systems?
I invite you to the discussion
Thank you very much
Best wishes
Nice discussion. In this case, the mission of voyager 1 and 2 can be mentioned. The two spacecrafts have been sent to the space with close time distance of each other 42 years ago to explore the solar system and its beyond. Still some parts of voyager 2 is functioning and sending data to the stations on earth and it is passing the heliopause and entering a new era and thereafter a new constellation. It is surprisingly sending unexpected news from beyond our planet and the whole solar system. In my opinion first of all such missions can be designed and performed to receive and send us the accurate data of the meta space outer our blue lively planet, then researchers can decide to manage sending existing humans to outer planet or better to say to plan building a new residential area on other planets. As an example after moon and mars the next destination can be the titan the moon of the planet Saturn. Titan with a thick atmosphere is a negotiable opportunity.
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Technological advances have amazed all of us. Do you think that is it or will it be possible to build a time machine?
Any discussions are welcome. But please give justifications for your opinions and discussions.
Dear Quan,
No, a "time machine" (I assume you mean by this a "time travel machine") is not feasible now, and never will be. For an explanation, please see my essay 'On the Impossibility of Time Travel,' which will be found at the following link: https://fqxi.org/data/essay-contest-files/Smith_IOTT6.cwk.pdf .
People who hold that time travel is possible fail to understand the fundamental nature of time. I hope you'll find my essay helpful in this regard.
Best,
J. C. N. Smith
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If so, when will new telescopes be constructed, thanks to which you will be able to see what is on the planets of other planetary systems in other constellations?
Every now and then more and more perfect telescopes are being built thanks to which photographs of other constellations and other galaxies are created.
Thanks to these photographs, the cognitive abilities in the field of astronomy are increased, among others the estimated amounts of stars, planetary systems and planets in specific constellations, galaxies.
Besides, thanks to these photographs, more and more perfect maps of the blue vault, collections of galaxies and specific segments of the cosmos are created.
For example, studies conducted in recent years based on new cosmic photographs show with previously unattainable accuracy the distribution of stars in the Milky Way Galaxy, in which there is a solar system with our Earth.
In April 2018, astronomers prepared a much more accurate than the current three-dimensional map of the Milky Way Galaxy.
This was done as part of a research project with a million dollars budget. As part of this research project and thanks to the space mission launched in 2013, the Gaia probe was developed a very accurate map of the Andromeda Galaxy and a new research material was created for the purposes of research into the analysis of the past and future of our Galaxy.
The research project was implemented by the European Space Agency. Based on this research project, the latest astrometric data set containing positions and self-movements of over a billion stars was made available.
Placed on Earth's orbit, the Gaia Probe has two optical telescopes and three scientific instruments that also allow to determine the brightness, temperature and chemical composition of individual stars.
In addition, the latest data set contains star colors that provide vital information about their surface temperature and age.
The Gaia probe also provided new data in the area of ​​13,000. asteroids circulating within the solar system.
In view of the above, the current question is: If so, when will new telescopes be constructed, thanks to which you will be able to see what is on the planets of other planetary systems in other constellations?
First let me offer a minor correction: "Constellations" are configurations of the stars that appear in the night sky from the surface of the Earth that were grouped together by the ancient Greeks to symbolize mythological and other creatures. Constellations have no physical significance but they are very handy ways to locate astronomical objects in the night sky.
Other than the planets of our own Solar System I doubt that there will every be on planet Earth a telescope capable of resolving the surface of a exoplanet. All we can do is analyze the light we receive directly from the parent star and that reflected by the star's exoplanet.
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There is some evidence about star formation on LMC clusters. I wonder if these clusters could change it metallicity during time.
The presence of multiple Main Sequence and Red Giant branches in old globular star clusters are due to abundance differences. Here are a few references reporting observations, and modeling by self-enrichment:
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I have observed rotation curve data of a galaxy, and I want to know what is the best and simplest mathematical model to find the galactic rotation curve and dynamical mass of such galaxy.
Dear Thierry De Mees,
I have downloaded your book "Gravitomagnetism/Coriolis Gravity Theory" and will spend my winter break reading through it. As I recall, in the past, Voyager images lead researchers towards the Coriolis effect as an explanation for the Great Red Spot on Jupiter. Thank you.
Sincerely,
Terry R. Fisher
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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.
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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I wonder how the gravitational radiation at speed of light has been taken account. When clusters collide, the information for changing the curvature doesn't make the repair at once but gradually, I think.
Could the dark matter observed as gravitational lensing be due to the delay of the changes in the gravitational field? The curved field continues its moving although the center massive objects collides...
Thierry, as your theory is non-standard, you need to prove logically and quantitatively your claims.  The way to achieve it is to publish your results in well recognized referred journals.   I found no publication of your part in the standard physics or astrophysics literature.   As you are Editor at the "General Science Journal",  self-publications there  cannot serve as a path to recognition by peers.  I do not remember to ever see a single citation from this journal, so it would be interesting to know its ranking, if it exists, among the journals in the field.
In your reply you write something confusing: "The angular momentum that is present in spinning structures and stars is effectively causing changes by the creation of an anisotripic gravity field upon long-lasting orbits.".    But angular momentum  is unrelated to gravity by definition, it is just a vector product of positions and velocities weighted by mass, and thus is unable in itself to "cause" a gravity field. The source of gravity  in Newtonian theory is mass, and mass-energy in GR.  So what you could argue is that in GR kinetic energy is causing some gravitational field contribution, but certainly not angular momentum.  In the strong gravtational regime, such as near black-holes, so not at all comparable to galaxies and galaxy clusters, space-time drags indeed test particles. This is the Lense-Thirring effect (1918). Its tiny effect around the Earth has been measured and found to follow GR predictions.  So what you say is nothing new, just that this effect is so tiny in galaxies and galaxy clusters that experts in the field know it is negligible and don't need to even discuss it further. If you think otherwise, show why generations of experts have been wrong and quantitatively by how much. For gaining audience it is insufficient to assert the former experts are wrong or "ridicule".
There is no need of an obscure explanation for understanding astrophysical disks.  The cause of flattness in such disks is energy dissipation in situations where angular momentum is better conserved. In galaxies radiative processes are efficient at exporting energy while inefficient at transporting momentum.  All this has been quantitatively tested by a large number of independent numerical experiments over decades.
Finally, your last two phrases are just incoherent. If your effect redistributes stars in an unexpected way,  surely the observed stellar distribution in itself would show a problem distinct from stellar kinematics and dark matter.  What is causing the dark matter problem is the combination of stellar distribution (mass density decreases ~exp(-R/h)) with its kinematics (which requires mass-energy density decreasing as R^-2).  If you think the disk rotational kinetic energy is able to explain the difference, you would need rotational speeds close to the speed of light to get any substantial effect, which is obvioulsy contradicted by the known speed of ~0.007 c.  Since kinetic energy is proprotional to the squared velocity,  the speed effect is actually ~10^6 times too small to match your claims.
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I have been reading Feynman lectures for sometime. In the volume 1 he mentioned that no model at that time could explain the formation of galaxies. Is the problem still unanswered? Please provide links or other information regarding the same topic. Thank you.
Dear Mr. Murthy,
We do understand the many physical processes involved for galaxy formation, the gravitational dynamics of matter clustering, the radiative processes, thermonuclear processes once stars form and some explode at the end of their lives. Maybe there is a supermassive black-hole that forms. Then we have to contend with both baryonic matter and (dark) non-baryonic matter. This clustering process starts and continues in an expanding universe. We have also observed in the Cosmic Microwave Background (CMB) the density fluctuations in the very early universe that are presumably the seeds of galaxy formation.
Thus, the complexity lends to a very involved model that is numerically calculated and we get structures resembling the galaxies we see. During Feynman's time the computing power did not exist to make such a detailed model. We are still far from a completely satisfactory model that explains a galaxy's structure at all scales and naturally produces the stars and chemical abundances etc. But it is an ongoing process to model galaxies.
Suketu Bhavsar
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It is well-known from many galaxy surveys that the value of gas fraction (gas to stellar mass/ surface density) increases as one moves along in the Hubble's tuning fork diagram, from Sa -Scd type. So, does any paper/book talks about the typical representative values of that fraction as a function of Hubble type?
You may have a look at Fig. 6 in the paper with results from the ALFAALFA survey: http://arxiv.org/pdf/1506.05081v1.pdf to find a recent plot of MHI/Mtot vs Mtot for local galaxies. H2 is missing but these data are scarce. You may find some recent data in paper by Leroy et al. If you want the specific relation between H I mass and morphological type there is an old nice paper by Roberts and Haynes here: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1994ARA%26A..32..115R&amp;data_type=PDF_HIGH&amp;whole_paper=YES&amp;type=PRINTER&amp;filetype=.pdf
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can any one tell me how to calculate the rotation curves in early -type galaxies (elliptical-lenticullar)? can I use the same equation for spiral galaxies?
Take \omega_0=vmax/(2*\pi*c), where vmax is the flattened or maximum tangential velocity, use this for ellipticals, barred spirals and spirals:
v(r)= vmax * \frac{omega_0 * r}{sqrt(1+omega_0^2 *r^2)}
for the rotation profile. r is of course in light years.
For the spiral shape of these galaxies use:
r=\frac{2*\pi}{vmax/c} * \theta
where r is in ly, and \theta is in radians. The constant 2*/pi is in ly per radian. It just works out that way.
Cheers.
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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.
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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I am interested in finding closure relations for the BBGKY-equations and came across an old article On the integration of the BBGKY equations for the development of strongly nonlinear clustering in an expanding universe'' by M DAVIS, PJE PEEBLES, Astrophysical Journal Supplement Series, 1977. I am used to closures where the three-particle correlations are either neglected or are approximated by Kirkwood's superposition principle, which appears ad hoc to me and is inaccurate for certain applications.
In the article by Davis and Peebles, something I haven't seen before was used, a scaling solution where n-particle correlation functions are approximated by a simple power law. It looks like this only works if the particles are far apart from each other and if there is no characteristic length scale in the particle interactions, which is the case for gravity. This made me curious: How useful did this approach become in Astrophysics simulations, is it still used or was this a dead end? If not, has there been any recent improvements on this approach?
Has such a scaling approach to the BBGKY-hierarchy been used in other areas of physics, like plasma physics where there is also a power law (Coulomb) interaction?
Thank you for your answer. If your truth would be embarrassing for me, it would also embarrass such icons of soviet physics as Bogolubov and Landau, and I'd be totally fine with being part of that axis-of-shame :-) I agree that one has to be careful with ensemble averages when talking about inhomogeneous systems, for example, when describing soliton-like waves in active matter (see my Phys. Rev. E from 2013, and the Discussion on Ohta paper in 2014)). However, I disagree that hierarchy-equations like the BBGKY-hierarchy are useless in general. In your own papers, you also use such hierarchies of equations for multi-point correlation functions. In my opinion, for the ensemble average, one just has to imagine that only  the proper microscopic members that describe a particular inhomogeneous state are part of the ensemble. For example, for a single soliton, only those microscopic states should be  included that have the same density and momentum profile (coarse-grained over small cells in phase space) at the same time. Another argument to not dismiss BBGKY-like hierarchies is to consider the extreme case of a N-particle ensemble distribution that consists of products of delta-functions at time t. That means, all ensemble members have particles at the same positions with the same momenta and the BBGKY-equations would be equivalent to the evolution of a particular real system with those initial conditions. A more pragmatic argument: I recently used the first two BBGKY equations (adopted to my system) for self-propelled particles in a weakly-correlated limit where three-particle correlations are negligible compared to two-particle ones and I found perfect quantitative agreement with particle-based direct simulations. I didn't have to explicitly select the proper members of the ensemble, I did neither use thermodynamics nor Gibbs distributions, I just solved the time-dependent hierarchy equations until  a stationary state was reached. Thus, if you have an alternative theory, I suggest testing it quantitatively with Molecular Dynamics simulations and see how it does. In contrast to experiments, simulations can be adjusted to mirror all the approximations made in a theory and thus allow comparing apples with apples''. In my opinion, the more serious problem with kinetic theory is the closure of the hierarchy. You mentioned in your papers that you somehow close your equations at the two-particle level but I couldn't find any details. For self-propelled particles, there is parameter ranges where the three-particle correlations are stronger than the two-particle ones and the four-particle-ones are even stronger than three-particle ones and so on. Thus, in this strongly-correlated system, some type of generating function should be found that contains correlations to all orders, at least approximately, or a systematic closure for all multi-particle correlations is needed. In your papers, you mention discrepancies between experiments and theory. Could that also be due to neglecting these higher multi-particle correlations or using an inappropriate closure ?

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I just was wondering how much the quantity of stellar mass (still burning hydrogen) has changed since its formation, from the different parts of our galaxy: disk, halo, bulge, solar neighborhood.
Some stars explode but they are the fewest, some others interact but they are the fewest - is this correct?
This used to be a more straightforward question 20 years ago. But observations have shown considerable mass influx into the milky way via small mergers and satellite infall thus allowing the stellar mass to grow slightly on scales of billion of years.
The average star formation rate in the Milky Way is about 10 solar masses per year.
A currently unknown astrophysical question is when did our Galaxy (and others)
reach their 1/2 mass point as defined by stellar mass (not dynamical mass) -
that probably took 5-7 billion years, but the question is not well constrained either by local data or by observations of galaxies at high redshift (when they were younger)
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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.
I also suggest a recent paper - http://arxiv.org/abs/1212.5317.
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Is the question wrong?
Not sure the word "huge" is needed but the basic question of interest is whether or not most of the baryons in the Universe are inside or outside of gravitational potentials (e.g. galaxies).
Agreed that understanding how the first generation of stars formed inside galaxy halos remains largely unknown.
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All theories attempt to explain known observations and make testable predictions.
I am not sure what 'truth' is in this regard.
The Big Bang hypothesis fits many of the known observed properties of the universe (red shifts, background radiation, etc.). It's not perfect, and may need alteration. I am unsure as to what the 'bouncing theory' is. Care to point to a peer-reviewed summary?
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In particular, the Jackpot (SDSS J0946+1006, Gavazzi et al 2006, Sonnenfeld et al 2012) seems to contain a significant quantity of dark matter, even in the central regions that are being probed by strong lensing.
Other analyses generally find an amount of dark matter comparable to the amount of luminous matter. This is also what we find. This can be explained by baryonic dark matter, no need for exotic matter. Our main point is that the constancy of M/L with radius is a strong argument against extended DM halos. Concerning the "Jackpot", the total amount of DM found is also comparable to the amount of luminous matter. However, the redshift of the source is not known (only a photometric estimate). We have ruled out such systems because they introduce unneccessary uncertainties compared to better characterized ones.
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