Unanswered Questions
227 questions with no upvoted or accepted answers
2
votes
0
answers
34
views
Local anisotropies in the expansion of the universe and tidal forces...?
In the context of the large-scale structure of the universe, there can be local anisotropies (https://www.aanda.org/articles/aa/full_html/2021/05/aa40296-21/aa40296-21.html).
I understand from this ...
- 1,017
2
votes
0
answers
70
views
How is an index of n=0 possible for the Lane-Emden equation?
I was recently showing that an index of $n=0$ for the Lane-Emden equation results in constant density throughout the star. However, in my calculations I had to use the constant $\alpha$ which can be ...
- 106
2
votes
0
answers
60
views
What could these LMC objects in this color-color diagram be?
I have performed a color-color and colour-magnitude plot of various sources detected in an LMC image (JWST NIRCAM F200W, F150W and F115W filters). I then also queried SIMBAD to collect relevant ...
- 21
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?
- 2,349
2
votes
0
answers
34
views
Could rogue planets with cold nucleus have winds or water currents/waves due to the planet's rotation?
Are there any types of wind or waves caused and produced only and exclusively by a planet's rotation? Not influenced by the planet's rotation, but produced solely by it?
In the case of waves, are ...
- 1,017
2
votes
0
answers
101
views
What is the correct way to represent the Parallax angle?
I was recently reading about the parallax effect and hence had a doubt about the parallax angle.
A lot of places mention the parallax angle as (θ1 + θ2)/2 while in ...
- 121
2
votes
0
answers
61
views
Is there an equation that can give position of a satellite around a parent body as a function of time?
I’ve been looking into this lately, and most sources I have used solve this problem numerically. I was thus wondering if there is a proper equation to solve for position without numerical, especially ...
- 201
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 ...
- 145
2
votes
0
answers
67
views
Finding the uncertainty in period for String-Length Minimization calculation
I wrote a Python script that calculates the period of an unevenly sampled data set using the String-Length Minimization method.
You can read about that method here: A period-finding method for sparse ...
- 2,349
2
votes
0
answers
115
views
Velocity of the object in Binary system
how to i can calculate the velocity of the object? If i know the distance of the object from the center of mass, and i know distance between the two (identical) ellipse center... (the two object has ...
2
votes
0
answers
255
views
Abundance of an element Xi in mass fraction from its abundance by number
How can I calculate the expression of the abundance of a given element Xi in mass fraction from its abundance by number Ni/NH, where log(NH) = 12 is the abundance by number of hydrogen?
I've tried the ...
- 4,800
2
votes
0
answers
29
views
Equation describing Energy Transport due to Radiation in the interiors of stars
I am considering a very elementary stellar structure and I'm required to derive an equation to describe the energy transport due to radiation. The answer I am supposed to obtain is:
$$\frac{dT}{dr}= -\...
- 779
2
votes
0
answers
42
views
"First gamma-ray eclipses from ‘spider’ star systems" - but have other types of gamma-ray eclipses been observed?
The January 28, 2023 NASA News item NASA’s Fermi Detects First Gamma-Ray Eclipses From ‘Spider’ Star Systems begins:
Scientists have discovered the first gamma-ray eclipses from a special type of ...
- 15k
2
votes
0
answers
54
views
How to show that $P_c=(9GM^2)/(14\pi R^4)$ from equation of hydrostatic equilibrium
I need to show that $$P_c=\frac {9GM^2}{14\pi R^4}$$
from the equation of hydrostatic equilibrium: $\frac {dP}{dr}=-\frac{GM\rho}{r^2}$
in the exercise before, we show that $\rho_c=\frac {6M}{5 \pi R^...
- 71
2
votes
0
answers
46
views
How do I calculate the flux density of a substellar object?
I am currently trying to generate photometric passband colors for brown dwarfs and planets generated through MESA (Modules for Experiments in Stellar Astrophysics). I believe I understand the ...
- 61