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My theory has G (Newton's Gravitational Constant) to be inversely proportional to the 4D radius of the Lightspeed Expanding Hyperspherical Universe (LEHU topology).
I need to simulate the Stellar Population under the epoch-dependent G assumption.
At this time, I consider that there should be a seed stochastic distribution of t_{ff} (which is inversely proportional to G*rho(0)
That distribution would be used over and over again to seed new stars at different epochs.
My problem is simulating the aging of previously triggered stars. For that, I need a consumption rate that is dependent upon GM. As far as I can tell, all star's processes are dependent upon the product and not just on the mass.
I welcome guidance.
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On the average, doubling the mass of a Main Sequence star increases its brightness by about a factor of 10, and reduces its Main Sequence lifetime by a factor of 5. For a rough but thorough discussion (intended for beginning college students), http://cseligman.com/text/stars/mldiagram.htm (The Mass-Luminosity Diagram and Main-Sequence Lifetimes) on my astronomy website.
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What was the light year distance to the original departure point:
of light arriving here and now from the most distant stellar objects?
I am not asking the travel distance, but fine to also mention that..
assume the current consensus of ongoing cosmic expansion, over the course of 13B rounded years, so that the current visible universe is 46.5B LY radius, so that the original departure point would be __x__ LY maximum
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I have added a short video presentation called How Far Away which helps with this question:
Deleted research item The research item mentioned here has been deleted
Richard
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Physics is one of the physical sciences. The two other physical sciences are chemistry and astronomy. Astrophysics is the branch of physics that deals with space and celestial bodies.
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@Weitter Duckss you just attacked the logical fallacy of "appeal to autority" and cite your own book in the same comment? It's not funny, but you make me laugh XD
"Astrophysics is a fabbrication of non-sense" is not satire, it's just you offending the work of hundreds of men and women; also satire is not a way of comunication in science.
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Dear Colleagues,
I am a liaison (informal) at my university between science and the arts. I have family in planetary astronomy but this is far afield.
A question or two:
What does this newly-reported Radcliffe Wave of gaseous proto-stars tell us about how our galaxy originated?
Is there any chance that this wave will make some difference in our own sun's behavior?
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Dear Preston,
Intriguin view, thanks for sharing Vera Lima
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A maser database like this has been well overdue!! Thank you so much for making it. 
Is there any plan to also include star forming regions? And how about methanol masers?
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I think Chibueze et al. 2017 (ApJ) has done an excellent work on that. Check it out.
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Is there a chance for cryo-pycnonuclear reactions to take place in the degenerate core of a white dwarf, affecting this way its stability?
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degenerate matter cannot quench nuclear reactions with pressure responses the way normal matter can since degeneracy pressure doesn't depend on temperature (not strongly anyway). so if any reactions were to occur inside a WD, they would rapidly lead to a runaway nuclear catastrophe. and as william pointed out, that would no longer be a WD.
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Is there any relationship exists between longitudinal magnetic field of stars with their chromospheric emmission.?
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Yes, indeed. Magnetic fields play important role in heating the chromosphere and the corona of the Sun and the magnetically active stars as well. For a comprehensive review you may visit e.g.:
or
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The most mysterious star in the universe. KIC 8462852 is fascinating and we should keep looking at it. could small mass produced tracking enabled sat dishes be calibrated via the internet to crowd search the sky in a coordinated fashion?
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Omar,
Yes.
But the problems of unpredictable latency mean that one would be unable to use an Internet-connected array to perform interferometry - so you won't get a more detailed picture.
At best one would simply 'stack' the images in a non-coherent fashion - akin to making a telescope with a higher sensitivity, but not a higher angular resolution. The picture will just be brighter - still not a bad idea.
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We know that the maser species usually used as evolutionary tracer for star forming region, one of my question  Is there is an evidence for the presence of OH maser molecule earlier than H2O maser in star forming region? 
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I don't know of any, and according to Ellingsen et al. 2007 IAUS and Breen et al. 2010, MNRAS 401, 242, and the references therein, there are indications that OH masers likely occur after water masers.
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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?
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There is a large body of literature on this.  There are basically two kinds of feedback from Stars to the ISM:
--Chemical evolution of the ISM
-Kinematic Feedback - which can involve shocks in terms of SN explosions but just massive star formation in spiral arms will do this.   In some 2D velocity fields  there is evidence for such kinematic star formation.
If all you want is an estimate, then make a model - how many SN events or O-Star formation events are there in the lifetime of a galaxy?
Note, in practice this is difficult, acretion disks or dense places in the ISM are likely the main inhibiting factors.  The ISM is not a smooth environment at all.
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After stay in the main sequence, what would the rate of star heart gravitational collapse look like in function of time for :
  • 0,1 to 8 solar mass stars (when evolving in red giants -> planetary nebulae -> white dwarfs)
  • 9 to > 30 solar mass stars (supergiants -> supernovae -> neutron stars / black holes)
Would it be an increasing exponential ? a succession of power laws ? anything else ?
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The gravitational collapse time of any object is simply
the inverse of the square root of G*rho  where rho is the mean density.
Now real stars don't gravitationally collapse but are supported by various sources of pressure (thermal, degenerate, etc) and they are subject to sudden changes
For instance, a neutron star does not smoothly forms, it forms in about 1 second during Supernova phase.   A white dwarf does form slowly from the contracting stellar core of the planetary nebulae but that rate is primarily determined by mass loss from the star which is highly variable.
So there is no "smooth" gravitational core collapse function for stars.
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Is convective envelope of solar type stars decreases with the increasing in their stellar mass? If so what is the reason behind it?
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Have a look at http://astronomy.sussex.ac.uk/~rcs/stelstr.html, Handout 11, to see the overall behaviour of convection zones in main-sequence stars. The figures are taken from Kippenhahn and Weigert's excellent book Stellar Structure and Evolution, Springer 1990.
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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?
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Well, technically outside the star is not a vacuum, there is a stellar wind that exerts a force on the magnetic field. Because the magnetic field strength of a dipole field decreases faster with radius than the ram pressure of the wind, the wind always wins in the end and tears open the field lines. The result is a field that effectively becomes a monopole at long distance.
How much this influences the configuration on the surface of the star depends, of course,  on the wind-strength.
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The atomic lines for a star are observed to be shifted relative to their normal positions. This is due to a radial velocity of the star (i.e. the component of the star’s velocity along the line -of- sight). If the shift of the H β line is Δ λ = +0.4 Å , what is the value and the direction of the radial velocity of the star?
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   Since the given wavelength shift delta lambda is positive, this is a red shift, i.e., the star's radial velocity points away from us. If lambda_0 is the known wavelength for this line, then we have: delta lambda/lambda_0 = v/c, where v is the radial velocity, and c is the velocity of light.  Solving for v, and putting on numerical values, I get: v = 24 km/s.
   (The above is the radial velocity; the star could also have a velocity perpendicular to this, which cannot be calculated by the Doppler effect.) 
   This is not new; Ghazem just said it.
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I want to find data on fusion reactions like the ones in carbon and oxygen buring processes (12C+12C, 16O+16O) but fusing the other isotopes of C and O. The same for nitrogen and fluorine, etc. 
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The currently best source for alpha- and proton-capture reaction (including (p,a) reactions) is in my view the compilation of Christian Iliadis and his group, see Nuclear Physics A 841 (2010) 1 (note this is a series of 4 articles in the same issue of NPA). On the 17O(p,a) reaction new results will come up soon, meanwhile you might want to look into Sergi et al., Phys. Rev. C 82, 032801(R) (2010), which is to my knowledge the most recent work.
Regarding 12C+12C (and likely the same for 16O+16O), this is much more difficult since the reaction is very complex, the experiment not easy and the mandatory extrapolation very uncertain, in particular down to astrophysical energies. To my knowledge astrophysicists very often still use Caughlan and Fowler, 1988, which is probably as good as any other source, if you keep in mind that the uncertainty is very large at astrophysical temperatures and probably heavily underestimated due to the problems mentioned above.
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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?
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"Would you then say that the central densities associated with Carbon ignition and gravitational collapse are not the same?"
Yes, that's exactly what I'm saying.
At densities we're concerned with GR is negligible and would be a secondary effect even to Coulomb corrections. And Jeffries is right that the WDs are essentially cold. I think the problem may be one of incorrect use of Chandrasekhar-mass WD in the literature. Strictly speaking, a Mch WD cannot exist, since the Chandraskhar mass is the limiting mass. All non-rotating WDs therefore must have a lower mass. When we say "Chandrasekhar-mass white dwarf", we always mean "near Chandraskhar-mass white dwarf". Why don't you try it out and integrate a hydrostatic profile using TOV. Pick a central density and see what mass you get. The effect will certainly be small compared to metallicity effects (e.g. how much Ne22), Coulomb corrections to the equation of state (it's a plasma) or even non-zero temperature.
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To my knowledge, the vast majority of white dwarfs and neutron star (WD+NS) systems appear as unresolved (am I right?), consequently WD+NS systems would be mixed up with isolated white dwarfs because of the magnitude/color dominance of the white dwarf companion. I bet that only in the cases of pulsar behavior the neutron star might give them away. However, not every neutron star is a pulsar, so I am wondering if there is a technique to unmask all the neutron stars that belong to close binary systems as WD+NS.
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James,
There have been a number of microlensing detections, but their candidacies as black holes are somewhat ambiguous.
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How can I find the list of Galactic AGB stars, including their distance?
Specifically, I like to know if alpha Herculis is THE closest AGB star to the Sun.
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The AGB star Mira (omicron Ceti) is very likely to be closer to Earth than alpha Herculis. It is probably the nearest to Earth. Here is a paper describing a catalog of AGB stars from IRAS
The catalog itself is available at
You will have to cross-reference the IRAS numbers with SIMBAD
to determine whether Mira is indeed the nearest.