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  1. J

    B Orbital parameters of stars orbiting Sagittarius A*

    Interesting animations by Yukterez, unfortunately it's a bit beyond me to calculate relativistic orbits at the moment Below is my 2nd attempt at a simulation using more stars
  2. J

    I Plummer distribution of stars

    I probably should at least put a few more equations in to make things a bit easier. Plummer's density is given by: \rho(r) = \frac{3M}{4\pi R^3}\left( 1+ \left(\frac{r}{R} \right)^2 \right)^{-\frac{5}{2}} where M = total mass of star cluster R = magic scaling parameter Now let X_{n} be a...
  3. J

    I Plummer distribution of stars

    Hi all, I refer to the following pdf document, in particular the appendix: http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1974A%26A....37..183A&link_type=ARTICLE&db_key=AST&high= End goal is to distribute N stars each having mass m (looks like equal mass stars is the easiest...
  4. J

    B Orbital parameters of stars orbiting Sagittarius A*

    Thanks for the link Loren I will check it out and yes would be to compare. I am going to try and create a more 3 dimensional perspective like Janus's and get the camera zoom around with some smoke/fog effects if I can ever figure out how to get it working. The smoke/fog is turning out to be a...
  5. J

    B Orbital parameters of stars orbiting Sagittarius A*

    After great difficulty I managed to get something uploaded to youtube. Below is my cubes/stars orbiting the black hole Not quite as good as Janus's but I plan to improve in subsequent simulations
  6. J

    B Orbital parameters of stars orbiting Sagittarius A*

    Ok I think I found the problem. Looks like there were 2 issues, the first one was user error on my behalf. That x-value discrepancy we were having was because I accidentally gave you the value for S14 rather than S13. The other issue was in the jungle of + and - signs I got one of them around...
  7. J

    B Orbital parameters of stars orbiting Sagittarius A*

    Nice camera work there Janus - you did well to extract data for 10 stars. tony873004 I take it the calculation for E is still cactus in your code01.html calculator? I thought my E=2.11 was pretty close
  8. J

    B Orbital parameters of stars orbiting Sagittarius A*

    I got those instructions from: https://downloads.rene-schwarz.com/download/M001-Keplerian_Orbit_Elements_to_Cartesian_State_Vectors.pdf Thanks for the new calculator I will play with the numbers and try to see whats going on. For the new data can I just set M=0 for all stars?
  9. J

    B Orbital parameters of stars orbiting Sagittarius A*

    I just dug up an old dusty book from the garage and found it gave the following for S1 \mathit{a} = 20.5 \text{ mpc} \\ \mathit{e} = 0.496 \\ \mathit{i} = 120.82 \text{ deg} \\ \Omega = 341.61 \text{ deg} \\ \omega = 115.3 \text{ deg} \\ P = 132 \text{ years} The trouble with this data...
  10. J

    B Orbital parameters of stars orbiting Sagittarius A*

    I was hoping it would be a simple fix of adding .0 to the integer values given in the table for S13 as it is the only star with integer values but doesn't look to be the case unfortunately, especially since all other stars are producing orbits. I am using 3.61 \times 10^6 M_{\odot} \approx...
  11. J

    B Orbital parameters of stars orbiting Sagittarius A*

    Unless I have miscalculated somewhere, the S13 star doesn't look to be in a relatively stable orbit. Based on that data it will fall into the black hole (in my simulation it gets flung into infinity after a few seconds). Noted that the uncertainty in the measurements for that particular star...
  12. J

    B Orbital parameters of stars orbiting Sagittarius A*

    Thanks for the detailed information, you probably saved me a few weeks by mentioning that semi-major axis trap. What I did was use the above info to calculate the initial position and velocity of the star S1 and then used Euler's method to calculate subsequent positions using 3.6 million solar...
  13. J

    B Orbital parameters of stars orbiting Sagittarius A*

    That's beautiful thanks tony873004. If I understand correctly, using the information below for the S1 star we have that M_{0} = 360 - \frac{360}{T} (t_{0}-P) using D=P which means M_{0} \approx 360 - \frac{360}{94.1}(2002.6 - 2016.25) Does that sound reasonable?
  14. J

    B Orbital parameters of stars orbiting Sagittarius A*

    Sounds great if you could find more complete and current data. Yes it does look like I need help converting to Cartesian coordinates. My main trouble is with the mean anomaly which isn't provided in the table. We have a\text{, } e\text{, } \omega\text{, } \Omega\text{, } i but no M_{0} =...
  15. J

    B Orbital parameters of stars orbiting Sagittarius A*

    Excellent thanks tony873004 that animation should it extremely easy for me to do the animation since it has the nice Cartesian coordinates. Were you able to do that animation using the orbital parameters in this thread or was it already done? Thanks Janus that table is looking better. Looks...
  16. J

    B Orbital parameters of stars orbiting Sagittarius A*

    I was going to try and do an animation of stars orbiting Sagittarius A* but can't seem to find any useful data for it. The Wikipedia page has some data https://en.m.wikipedia.org/wiki/Sagittarius_A* and was trying to reconcile this with https://en.m.wikipedia.org/wiki/Orbital_elements since I...
  17. J

    Python Making a pretty n-body simulation

    Lots of good suggestions thanks everyone. I will get around to all 3 suggestions eventually but looks like blender will keep me occupied for a while
  18. J

    Python Making a pretty n-body simulation

    Hi newjerseyrunner, I did see something mentioned about OpenGL but don't know enough about it to answer your question. I'm currently exploring the blender suggestion. Thanks
  19. J

    Python Making a pretty n-body simulation

    Great thanks BOAS I did have a brief 5 second look at blender so it's good to hear your endorsement for it. I will focus my attention on blender now
  20. J

    Python Making a pretty n-body simulation

    Hi all, I have recently created an nbody simulation in Vpython for a few thousand particles where each particle is about 4000 times the mass of our Sun. Vpython is doing exactly what I want it to do the only problem being the output is extremely low quality (black spheres on a white...
  21. J

    Mass of a Cone with varying Density

    I think LCKurtz is correct but just to be clear, I do believe there will be a \pi in the answer. It will be hidden inside B
  22. J

    Newtonian mechanics and inclined planes

    hi, i am interested in finding a website which has lots of questions (and solutions) on newtonian mechanics to test my knowledge. things i had in mind include applications of F=ma,inclined planes, tension on ropes,springs etc. thanks
  23. J

    Fractional Brownian motion

    why do they call fractional Brownian motion, fractional Brownian motion?
  24. J

    Fractional Brownian motion

    hey there, i'm curious as to why they call it fractional Brownian motion. please don't say its Brownian motion that is fractional :tongue2: many thanks
  25. J

    Powers of sums/Fractional exponents

    for your first problem, as it stands (x + 5)3 = 3x + 15 but i think you meant to say (x+5)^3 you can do this by applying the following twice (a+b)^2=a^2+2ab+b^2 (a+b)^3=a^3+3a^2b+3ab^2+b^3 so (x+5)^3=x^3+15x^2+75x+125
  26. J

    Change of variables for PDE

    hi, i am having difficulty trying to find a change of variables to solve this partial differential equation \frac{\partial f}{\partial t} = t^\gamma \frac{\partial ^2 f}{\partial x^2} not sure how to pluck out a change of variables by looking at the equation as its definately not obvious to the...
  27. J

    Related rates of increase

    hey guys, just wondering if i did this correctly a spherical balloon is to be filled with water so that there is a constant increase in the rate of its surface area of 3cm2/sec . a) Find the rate of increase in the radius when the radius is 3cm. b) Find the volume when the volume is...
  28. J

    SATA hard disk

    hi, a friend is heading over to malaysia in the next few days and asked me if i wanted a 10000rpm ( 8mb cache, SATA ) 74 GB WESTERN DIGITAL 10000RPM hard disk. i would say yes but i am not sure if it will work on my pc my motherboard is an ASUS P4P800SE with Intel 865PE Chipset can someone...
  29. J

    I'm so lost! Volume and tension?

    you already have the density and dont need to work it out mass of the ball = 0.3kg density of the ball = 100kgm^(-3) re arrange your density formula to solve for volume, v v=m/d insert numbers and out pops the volume v = 0.3/100 m^3
  30. J

    Parallel transport

    hi, i am trying to show that the amount by which a vector is rotated by parallel transport around a triangle whose sides are arcs of great circles equals the excess of the sum of the angles over 180 degrees. this is what i have found out so far call the angles of the triangle (assuming...
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