# Questions tagged [modeling]

Questions which are asking about the mathematical formulations whose theoretical and numerical analysis provides insight, answers, and guidance useful for the originating application.

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### When will the number of stars be a maximum?

There are very roughly a "mole" of stars in the universe. Wikipedia quotes an estimate of $3 \times 10^{23}$ though the number is associated with some debate and uncertainly. I'd like to know if ...
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907 views

### analemma for a specified lat/long at a specific time of day?

I have in mind to do a yearlong photo project of the solar analemma. Can someone suggest a software program that will provide (& chart) the altitude and azimuth of the sun, for a given location, ...
531 views

### How do comets' nuclei stick together?

Comets are commonly called icy dust balls or dirty snowballs and as such rather light: Known comets have been estimated to have an average density of $0.6 {\rm g}/{\rm cm}^3$. Because of their low ...
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### What does this tweeted Astronomy Plot of the Week mean? What does it represent?

Twitter user BenneHolwerda (@BenneHolwerda) recently tweeted August 10 Astronomy Plot of the Week: And I think @SabineBellstedt and @_jessthorne summary graph deserves a spot for sure. If you work ...
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548 views

### Why does the convective core in an intermediate- to high-mass star shrink?

The image below shows the evolution of the hydrogen mass fraction profile for a 5 solar mass star in the main sequence. I would expect that the size of the convective core stays roughly constant as ...
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371 views

### DAMIT how do they get 3D shape and rotational trajectory of a tumbling asteroid from photometry?

This question asks about an algorithm used in Project DAMIT. @RobJeffries' answer led me to Wikipedia's William Herschel Telescope which led me to Wikipedia's 2008 TC3 which led me to the animation ...
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167 views

### Modeling egg shaped stars

I am well aware of one-dimensional stellar models: The simplest commonly used model of stellar structure is the spherically symmetric quasi-static model, which assumes that a star is in a steady ...
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490 views

### Convert from Jy/beam km/s to W/m$^2$

I need to compare some ALMA observations of a protoplanetary disk to disk-integrated fluxes obtained from a model. The ALMA observations are upper limits of non-detected spectral lines, where the RMS ...
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99 views

### Physical Meaning of the Principal Tidal Fourier Modes and Their Integers

I'm trying to understand tides evolution of planets, and I often come across the Prinicipal Tidal Fourier Modes expressed as: $$\omega_{lmpq}$$ For example, see the discussion after Eq. A15 in ...
107 views

### How did astronomers "measure a large (>40 degrees) misalignment between the black hole spin and the orbital spin" of MAXI J1820+70?

Gizmodo's Funky Black Hole Is Spinning Tilted says: A team of astronomers recently observed an askew black hole just 10,000 light-years from Earth. The black hole’s spin axis is out of alignment with ...
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### What does "RV model including a GP with a quasi-periodic covariance structure" mean?

A candidate short-period sub-Earth orbiting Proxima Centauri says: 4.1 Simple periodogram analysis ]We first consider a very simple pre-whitening procedure applied to the CCF RVs in order to ...
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97 views

### Angles in Ptolemaic Model

I am about to work with Ptolemy's Model for the motion of an upper Planet (Mars). I use a epicycle rolling on the deferent. As a first step, I am just interested in the shape of the trajectory, which ...
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### Dynamical modelling of galaxies with counter-rotating components using the Schwarzschild method

I am currently trying to understand dynamical modelling using Schwarzschild's method. I have been doing some reading the past days, but I suspect that I am getting something really wrong. According to ...
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80 views

### How to flatten 3d astronomical coordinates into 2d polar form in Python

I first asked this at Stack Overflow but got redirected here I am making a 2d simulation of the solar system. For that you need a starting point for all planets. Right now I am storing that data in ...
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### Basic, learning examples of applications of CFD and MHD in astrophysics, and current research directions using these techniques?

I am an undergraduate in Physics, and I have an opportunity to work with a some of my seniors to learn Computational Fluid Dynamics (CFD) and Magnetohydrodynamics (MHD). I would like to choose my ...
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### Which static spherically symmetric perfect fluid solutions of Einstein field equations are known to be suitable for stellar models?

Wikipedia's (Static spherically symmetric perfect fluid) short list ends in 2005 and lists only in total 5 such solutions. Does somebody know more?
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### Find position of orbiting body along orbit efficiently

I'm coding a game, and a fundamental mechanic is celestial bodies moving in elliptical, Keplerian orbits around a single gravitational point in a planetary system (not our solar system). The bodies ...
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### Conversion of 1D plot in 3D plot gives different physics

I am to track the path of a particle due to Lorentz force of the planet magnetic field, assuming there is no gravitational force on it. The equation of motion due to Lorentz force in rotating ...
84 views

### How to model blazar light curves

I have SED data spanning over a couple of days and I'm able to find the parameters of the SED (R, B, break energy,...) using least squares method. My question is how to model light curves (with t_acc, ...
1 vote
134 views

### What if you 'placed' the Chicxulub asteroid onto the Earth? [closed]

We all know what sort of devastating impact an asteroid could have if it collided with the Earth. But I'm curious to know what the effects would be if you removed the speed element from it, and were ...
1 vote
43 views

### Mathematical modeling of the influence of components of the interstellar medium on the distortion of the wavefront of the observed object

Associated with: Flowchart of the pipeline of key processes for modeling wavefront distortion of astronomical objects: ground-based observation case Let's imagine for a moment that we are outside the ...
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1 vote