Skip to main content

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.

Filter by
Sorted by
Tagged with
29 votes
1 answer
3k views

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 ...
uhoh's user avatar
  • 30.7k
9 votes
3 answers
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, ...
Bruce Simonson's user avatar
9 votes
1 answer
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 ...
B--rian's user avatar
  • 5,626
8 votes
2 answers
1k views

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 ...
uhoh's user avatar
  • 30.7k
8 votes
1 answer
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 ...
Stefano's user avatar
  • 199
8 votes
2 answers
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 ...
uhoh's user avatar
  • 30.7k
7 votes
1 answer
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 ...
B--rian's user avatar
  • 5,626
7 votes
0 answers
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 ...
lucas's user avatar
  • 1,386
6 votes
1 answer
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 ...
ValientProcess's user avatar
5 votes
1 answer
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 ...
uhoh's user avatar
  • 30.7k
5 votes
1 answer
476 views

Orbital modelling, three bodies, leapfrog numerical integration

Apologies for the length of this question. I'm modelling the motion of a single planet around the Sun using the equations: $$dv_{x_{i}}/dt=a(t)=-GM_{SUN}x_{i}/r^{3},$$ where $x_{1}=x$, $x_{2}=y$ and $...
Peter's user avatar
  • 1,033
5 votes
2 answers
401 views

What is the actual visual characteristics of a black hole?

Is there a safe distance in which a black hole can be observed with the human eye? What is a safe distance? I have seen many computer simulated and artist renditions, and I am not sure if they ...
Muze's user avatar
  • 1
5 votes
0 answers
203 views

Different techniques for calculation of celestial bodies dynamics with different time-scales

Differential equations describing the dynamics of celestial bodies (rotation, nutation, precession and other effects) can be solved numerically, which makes it possible to study their general non-...
ayr's user avatar
  • 825
5 votes
0 answers
52 views

Extract surface density profile from a temperature profile?

I have a protoplanetary disk model which outputs a temperature vs. radius profile, based on radiative transfer. Looks something like this... One of the inputs to the model is the surface density ...
lucas's user avatar
  • 1,386
4 votes
2 answers
364 views

What good is the Einstein de-Sitter model?

Why is the EdS model still taught and used to predict the age of the universe if ours is not an EdS Universe. Does this model have any pros?
Arnab Chowdhury's user avatar
4 votes
1 answer
106 views

How to model and subtract nebular emission lines from stellar spectrum

I have optical stellar spectra from a star forming region with spatially varying nebular background. I want to subtract the nebular lines from the stellar spectra (which are varying in intensity from ...
pziphi's user avatar
  • 71
4 votes
1 answer
112 views

How do various astrophysical models deal with so many orders of magnitude in scale? Are there completely different models for different scales?

If we just model our solar system's dynamics, one could use a straightforward numerical integrator with all n(n-1)/2 gravitational interactions along with some torques and non-gravitational forces. ...
uhoh's user avatar
  • 30.7k
4 votes
2 answers
395 views

Numerical Programming using ODEINT takes more than 17 minutes

I am trying to track the trajectories of a charged particles under the influence of Gravitational and Electromagnetic effect. Computing for time points, t0=0second -tf= (36002430)sec with stepsize 0....
Lunthang Peter's user avatar
4 votes
1 answer
230 views

Using cosmological model GADGET - 4

I want to use GADGET-4 "a parallel cosmological N-body and SPH code meant for simulations of cosmic structure formation and calculations relevant for galaxy evolution and galactic dynamics" ...
SlightDecoy's user avatar
4 votes
1 answer
163 views

Why does the precession of the earth affect other planets?

In the Wikipedia article on numerical integration of planetary motion it states: ...the flattening of the Earth causes precession, which causes the axial tilt to change, which affects the long-...
Tyler Durden's user avatar
4 votes
1 answer
69 views

Which galaxies have the most well known / estimated dark matter halos?

For this I guess you need accurate circular velocity measurements of the stars in the galaxy a decent luminosity profile for the galaxy some analysis which looks at the discrepancy between the two ...
Suzie Q.'s user avatar
4 votes
1 answer
81 views

Effect of particulates on the visibility of stars?

I am looking for a (mathematical) relationship - either empirical or theoretical - which quantifies how the visibility of celestrial objects decreases with increasing amount of particulates in the air....
B--rian's user avatar
  • 5,626
4 votes
1 answer
145 views

Brown Dwarf Cloud Models

There has been research that suggests that the changing brightness of Brown Dwarves are due to bands of Iron/Silicate clouds. Several models have been made that supports that hypothesis. My question ...
Hippeus_Lancer's user avatar
4 votes
1 answer
262 views

How to derive gravitational-wave frequency vs time from strain vs time

Suppose I have a time-series of the gravitational-wave strain amplitude as a (discrete, i.e., an array of numbers) function of time. The figure below is just illustrative. I am not using measured LIGO/...
Daddy Kropotkin's user avatar
4 votes
0 answers
158 views

Time evolution data of the Great Red Spot on Jupiter?

Jupiter's Great Red Spot fascinates scientists for ages, so it does me. Where can I find a table (e.g. as CSV-file) with the time evolution of longitude, latitude, horizontal and vertical extension of ...
B--rian's user avatar
  • 5,626
3 votes
2 answers
235 views

2 points on Earth’s surface, 1 second apart in time

I’m hoping to find a method (probably some modeling software?) that would allow me to find pairs of locations on the Earth’s surface that occupy the same point in space relative to the sun, one second ...
Erik's user avatar
  • 133
3 votes
1 answer
230 views

The sun "burns" hydrogen and even has "campfires" on it, but has anyone calculated a rate of actual chemical burning on the Sun?

Answers to Hydrogen burning vs Hydrogen fusing explain that in astrophysics "burning" generally refers to nuclear fusion or at least nuclear reactions1, and information at Why didn't we ...
uhoh's user avatar
  • 30.7k
3 votes
1 answer
54 views

Does a replacement exist for Dexter? (A tool that reconstructs data from a pdf of a graph)

Dexter was a tool from the German Astrophysical Virtual Observatory, made by the Center for Astronomy of Heidelberg University (ZAH). It was able to reconstruct data from a graph if you provided a pdf ...
Capp's user avatar
  • 31
3 votes
0 answers
68 views

Is there software that will let me calculate things like lunar phases and the position of bodies in the sky in a custom solar system?

I am constructing a fictional solar system and want to be able to calculate astronomical events and locations, like lunar phases and eclipses, plus the positions of other astronomical bodies in the ...
Lawton's user avatar
  • 131
3 votes
0 answers
95 views

How to take into account the filter response in thermal and reflected flux density calculations?

I'm using python to calculate the thermal and reflected flux densities of a faceted asteroid model, where both equations have the Planck function present in them. Currently, I'm integrating the Planck ...
Rahoul's user avatar
  • 41
3 votes
0 answers
86 views

Measured values of the solar irradiance at other values than 1 AU?

It is straight forward to estimate the total solar irradiance of a planet using the Earth's solar constant, and scaling it according to the (mean) distance of the planets. But for which planets have ...
B--rian's user avatar
  • 5,626
3 votes
0 answers
75 views

Clarity on dust extinction terms and implementation: $R_V$,$ A_V$, and $E(B-V)$

I have created a model galaxy spectrum using STARBURST99 and want to compare it to an observed spectrum of a particular galaxy. I understand that I need to redden ...
curious_cosmo's user avatar
2 votes
4 answers
3k views

Can we violate law of physics in any other planet? [closed]

Can't there be any way to violates any law of physics? If in our earth we can't violate any law of physics can't we violate in any other planet?
Shaun's user avatar
  • 47
2 votes
2 answers
185 views

Has stellar evolution ever been modeled analytically?

I'll still remember the handout my astronomy professor gave us more than several decades ago; Our Friends the Polytropes. We spent a lot of time learning how polytropes, simple analytical power-law ...
uhoh's user avatar
  • 30.7k
2 votes
2 answers
327 views

Measure the deprojected distance between two points?

I have an image of a protoplanetary disk, from which I would like to measure the distance of various points from the centre. See below image for an example, where I would like to measure the distance ...
lucas's user avatar
  • 1,386
2 votes
2 answers
135 views

Estimate prevalence of ʻOumuamua-style interstellar obects inside Jupiter orbit now that C/2019 Q4 (Borisov) is found?

Now we know two of them, so maybe it's not an outlier. We have two points so we can draw a line. How many similar macroscopic objects should be zipping through space at ~30 km/sec so that we would ...
alamar's user avatar
  • 145
2 votes
1 answer
143 views

Orbital modelling - best choice for initial JPL Horizons data?

I'm modelling planetary orbits using a spreadsheet and Feynman's numerical method given here. I have put together a spreadsheet (10,000 rows) to model Mars' orbit in three $\left(x,y,z\right)$ ...
Peter's user avatar
  • 1,033
2 votes
1 answer
69 views

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 ...
uhoh's user avatar
  • 30.7k
2 votes
1 answer
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 ...
Joe_base's user avatar
2 votes
1 answer
116 views

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 ...
AstrOne's user avatar
  • 335
2 votes
1 answer
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 ...
Tmpecho's user avatar
  • 45
2 votes
2 answers
170 views

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 ...
Mirae's user avatar
  • 65
2 votes
0 answers
44 views

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?
JanG's user avatar
  • 129
2 votes
0 answers
89 views

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 ...
w94n9's user avatar
  • 51
2 votes
0 answers
101 views

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 ...
Lunthang Peter's user avatar
2 votes
0 answers
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, ...
Andrija Župić's user avatar
1 vote
1 answer
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 ...
user avatar
1 vote
1 answer
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 ...
ayr's user avatar
  • 825
1 vote
1 answer
34 views

Flowchart of the pipeline of key processes for modeling wavefront distortion of astronomical objects: ground-based observation case

Associated with: Mathematical modeling of the influence of components of the interstellar medium on the distortion of the wavefront of the observed object Being inspired by this article, as well as ...
ayr's user avatar
  • 825
1 vote
2 answers
367 views

How can I get/generate/extract PSF image from galaxy .fits image?

I want to model an image of a galaxy from Hubble. For this, I need the PSF image as well. I already tried to use TinyTim, but I don't have half of the parameters and cant be sure about the quality of ...
Igor Kolesnikov's user avatar