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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How to model galactic rotation curves?

I have R (kpc)- distance from galactic center and v(km/s) rotational speed at that distance. I was thinking of creating a simple model comprising of 3 terms 1 for Keplerian component another for rigid ...
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2 votes
2 answers
77 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 ...
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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 ...
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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 ...
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5 votes
1 answer
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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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Can we use atmospheric retrieval techniques on stars?

Although there are lots of examples of atmospheric retrieval techniques being used on exoplanets, and recently brown dwarfs, I can't find any mention of atmospheric retrieval techniques being used on ...
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2 votes
1 answer
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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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what is the difference between Composite Stellar Population and Galaxy Spectral Energy Distribution?

I am reading Conroy et al. (2013), an extensive review on Stellar Population Synthesis technique, and I really can't get the difference between Composite Stellar Population and Spectral Energy ...
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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/...
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4 votes
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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 ...
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3 votes
2 answers
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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 ...
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Was the Nobel prize for gravitational waves handed out based on a hand-drawn theoretical curve? Has the data been fit more rigorously now?

In Sabine Hossenfelder's November 2019 video "Have we really measured gravitational waves?" (transcript, video), Sabine mentions the now famous image of the generally agreed-upon-to-be-very-...
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8 votes
2 answers
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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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6 votes
0 answers
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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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3 votes
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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 ...
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2 votes
2 answers
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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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1 answer
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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 ...
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0 votes
1 answer
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Disk-integrated vs disk-resolved, what is the difference?

I'm trying to find online what is the difference between disk-integrated vs. disk-resolved, but I can't find a website which does explain them, especially in the context of modelling spectral flux ...
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1 vote
1 answer
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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 ...
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3 votes
0 answers
60 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 ...
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4 votes
1 answer
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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....
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3 votes
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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 ...
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9 votes
1 answer
487 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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4 votes
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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 ...
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7 votes
1 answer
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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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1 vote
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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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3 votes
1 answer
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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 ...
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1 vote
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Details of the M87 Active Galactic Nucleus -- questions of scale

This video describes a scale model of the M87 SMBH (somewhat distorted to live in flat space and for other practical reasons) in which the Schwarzschild radius appears to be scaled to about 10cm, with ...
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1 vote
0 answers
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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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1 vote
2 answers
153 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 ...
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1 vote
0 answers
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Model/Infographic of plane of orbits and rotations planes of solar bodies (including their moons)

Is there a model/infographic with emphasis on the orbit and rotation plane of solar bodies? Of course, no scaling is needed for the size or distance. I remember reading there is one planet where the ...
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2 votes
0 answers
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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, ...
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1 vote
0 answers
26 views

Light profile fitting related questions

I am computer scientist and now I'm working with some astrophysical projects. During this work I accumulated some questions and maybe here I would be able to find some answers or advice where to look ...
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4 votes
2 answers
229 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?
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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?
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8 votes
1 answer
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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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2 votes
2 answers
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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 ...
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4 votes
1 answer
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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 ...
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4 votes
1 answer
124 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 ...
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1 vote
0 answers
19 views

Brown dwarf cloud models [duplicate]

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 ...
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1 vote
1 answer
98 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 ...
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28 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 ...
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2 votes
0 answers
48 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 ...
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5 votes
2 answers
300 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 ...
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1 vote
0 answers
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How do you fit a model SED to an observed galaxy spectrum with photometric data?

I have a spectrum of a galaxy from HST data and SDSS data (resulting in a nearly continuous SED from the FUV~1000 Angstroms through infrared). I have created a model SED with the galaxy simulation ...
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0 votes
1 answer
445 views

What is the lyman-werner background?

I've seen several papers that discuss the Lyman-Werner Background (LWB) when modeling star and galaxy formation in the early universe. One in particular (https://arxiv.org/abs/1803.04527) even varies ...
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2 votes
2 answers
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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 ...
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4 votes
1 answer
126 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-...
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