Questions tagged [astrophysics]
Questions involving the physics of the universe, especially the nature of astronomical objects, energy fields, and/or regions, rather than their positions or motions in space.
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Flux from the Sun on the Earth using the Stefan-Boltzmann law
What is wrong with this computation, plase? I am getting the result of 4291.65 W m^{-2} instead of 1361 W m^{-2}. Thank you very much
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Consistent values for density of galaxies between degree squared and steradian
I have a table of densities of galaxies :
Expected number density of galaxies for photometric survey per unit area and redshift intervals, $\mathrm{d} N / \mathrm{d} \Omega \mathrm{d} z\left[\mathrm{...
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Hierarchy of gravitational interactions of astronomical objects: from single to large-scale structures
Hierarchical structure is clearly visible in the Universe. The "observable universe" includes almost empty voids, between which lie large cosmic filaments. The filaments consist of galactic ...
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The Poynting Robertson Effect
In the Poynting Robertson effect, it says in general, the Poynting Robertson effect is caused by the fact that objects like dust re-emit the light they absorb. Is that correct? Is this effect weak? ...
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What would be the new Equation of motion if the magnetic field's origin is shifted from the origin of a co-rotating spherical polar coordinates?
The equation of motions due to the dipole magnetic force of a planet in a frame corotating with the planet and origin at the centre of planet assumed to be sphere components wise are given as below:
\...
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What happens to a binary star system when one of the stars explodes and loses a lot of mass
If one star of a binary system explodes and leaves a remnant. The remnant would still have the velocity but lack the mass of the original star.
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How to plot different curves in the same polar cordinates in matplotlib?
I tried to plot the paths of particle of different sizes in the same polar coordinate using the code given below using matplotlib. somewhat like this:
Instead I got this plot:
while the path for ...
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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. ...
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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 ...
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Would water freeze on Neptune?
Someone told me that water would boil on Neptune because of the pressure. But this seems suspect to me. Given a temperature of -353 Fahrenheit, I'd expect water to freeze pretty much instantly. So ...
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If a cluster of stars in dynamical equilibrium falls into a much larger blob of dark matter, will it get hotter and expand? Will it stop?
This question is inspired by ProfRob's inspiring answer to Are there really confined Globular Clusters? in which he invokes the concept of "virialization" where a dynamical system reaches ...
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Gas mass and velocity in galaxy
I was going through the SPARC data on galaxies (http://astroweb.cwru.edu/SPARC/)
The velocity of gas in the SPARC data is in http://astroweb.cwru.edu/SPARC/MassModels_Lelli2016c.mrt
The gas velocity ...
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What is value of charge by mass ratio (q/m) for a spherical micro charged particle with surface potential 6 volts in S.I units and in e/amu units?
In Liu and Ip (2014),The Astrophysical Journal, 786:34 (8pp), the value of q/m is derived as follows :
"for a dust grain with radius 'a', from $\phi = \frac{4\pi q}{\varepsilon_0 a}$ we have $\...
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Crop a FITS file in shape of another
I have a FITS file, let us say file A. I have another FITS file, file B. File B has a smaller footprint than file A. I want to crop file A in shape of file B. How do I go about doing that?
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When analyzing a particle moving at Kepler speed, √(GM/R) in a planetary magnetic field, do we need to convert it to angular speed, √(GM/R^3)?
A charged particle is moving in a planetary magnetic field, in a spherical polar coordinates which is corotating with the magnetic field. To solve the equations of motion numerically what would be the ...
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Can a star have one forbidden line or does it have to have many?
My question is: Can a star have one forbidden line, or does it have to have multiple?
Some Examples
I'll be using the O ᴠɪɪ line as an example.
ζ Puppis is a well studied O4Ief star with the O ᴠɪɪ ...
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Is the magnetic permeability (mu_0) necessary in the expression for planetary magnetic field?
To numerically analyse the Lorentz effect due to the magnetic field, say, radial component on a charge particles which of the expression would be correct, $\{ B_r = \frac{2R}{r^3} g_1^0 \cos(\theta) \}...
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calculating mass of galaxy from luminosity
A very elementary question, just to make sure I got this thing right.
Suppose we are given that the mass to luminosity ratio of a galaxy is $2 \frac{M_{\odot}}{L_{\odot}}$.
Let us say, that the ...
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Formula for "gravity assist"
I am familiar with the concept of "gravity assist" by which a space probe or other object, passing near a moving planet, can pick up some of the planet's orbital velocity.
I presume that ...
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Why is nuclear pasta the strongest part of a neutron star?
From my very rudimentary understanding of neutron stars taken from the abstract to "Elasticity of Nuclear Pasta", nuclear pasta is the strongest substance, hence the strongest part of a ...
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Why can't dark energy be considered a 5th fundamental force?
So I have recently been researching for multiple articles about fundamental forces, currently there are just 4 forces:
Gravity
Electromagnetism
Strong nuclear force
Weak nuclear force
So far there ...
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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 ...
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Elliptical galaxy classification
The elliptical galaxy (Hubble) classification goes from E0 to E7, with E0 being spherical and E7 being the most flattened. I understand that the angle at which the elliptical is viewed affects this ...
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Core radius of King's model
I've been learning about the King's model for globular clusters and have been taught that it assumes a core radius:
$$r_c = \sqrt \frac{9\sigma^2}{4\pi \rho_0 G} \ (1)$$
where $r_c$ is the core radius ...
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Public data for calculating equilibrium temperature of exoplanets
I am a high school student beginning a simple independent project to calculate the equilibrium temperature of exoplanets. I'm curious to see how many exoplanets have a similar equilibrium temperature ...
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Concerning a binary system of stars/planets/black holes could one of them be ejected before eventually merging or colliding?
I was having a discussion with an undergraduate student of physics about binaries and their interactions with external celestial bodies (which could cause the ejection of one of the members in the ...
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is there any direct method to calculate gravitational wave frequency if the source mass is known?
Suppose we have neutron stars of 8 and 9 solar masses, they both merge and produce a GW. How does one find the frequency of the GW? Is there any specific formulae to compute it?
What I want to know is ...
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Is there such a thing as a map that shows the current (not observed) positions of celestial objects?
As I understand it, maps of the sky and three-dimensional maps of the universe all show the observed positions of celestial objects.
Are there any maps that show our best guess at their current ...
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Gravitational recoil with stars/planets...?
When two black holes are merging, the resulting merge can be ejected if one of the black holes had less mass than the other one, so the gravitational waves emitted by both of them is unbalanced, and ...
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How long would it take for a black hole of the mass of mercury to evaporate? [closed]
Mass of mercury, formula of time taken to evaporate by a black hole
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Why is final kinetic energy zero for escape energy calculations?
When the question is about the minimum speed to reach a certain point, we would usually use conservation of momentum, i.e. $\mathrm{E_k + E_p}$(initial) = $\mathrm{E_k(0) + E_p}$(final). I am curious ...
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Can rings last around planets indefinitely?
Apparently, Saturn is losing its rings (https://weather.com/en-IN/india/space/news/2023-05-04-saturn-is-losing-its-rings-webb-may-tell-us-how-long-they-have-left) However, is there any way or ...
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Do all orbits emit gravitational waves?
In principle, all orbits in the universe should progressively decay due to the emission of gravitational waves. However, does this always happen? Are there any kind of orbits that do not decay as they ...
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Typical astronomical and astrophysical problems in various programming languages
As a rule, work in the field of observational astronomy and astrophysics requires knowledge of such programming languages as: C/C++ and the principles of OOP, MPI, CUDA. Sometimes additional ...
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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 ...
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Why is the dark matter component of MOND important in central regions?
A lot of papers say that even the theory of MOND requires the existence of dark matter, particularly in the central regions. However this is a bit counterintuitive to me considering that rotation ...
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What are the primary astrophysical implications of a proposed mass of about 11 M⊙ for the SN 2023ixf progenitor?
The abstract of the arXiv preprint SN 2023ixf in Messier 101: A Variable Red Supergiant as the Progenitor Candidate to a Type II Supernova (itself recently "discovered" in the observatory) ...
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Is the Sun hotter today, in terms of absolute temperature (i.e., NOT total luminosity), than it was in the distant past?
I am constantly reading that the Sun is at least 20% 'hotter', in terms of total radiation/luminosity, than it was a few million years after its formation (i.e., after the Hayashi stage...)
But what ...
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What was FJM Stratton doing during Kamishari Expedition 1936, linked to Pearl Harbor intelligence?
In 1936, FJM Stratton, renowned Cambridge prof astrophysicist-radioastronomer, less-known but true, GC&CS-GCHQ intelligence officer and specialist FJM Stratton, led his Kamishari Expedition to ...
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How to plot the freeze out equation for massive particle species in Mathematica? [closed]
I want to recreate the figure . This comes from the Cosmological Boltzmann equation which can be modified as the number density equation as
$$\frac{dY}{dx}=-\frac{s(m)<{\sigma}|v|>[y^2-Y_{eq}^2]}...
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Seeking Guidance & Tips for Collaboration on a Cosmological Project Involving Potential Energy Variation Due to Cosmic Expansion
I'm a student with a deep interest in cosmology and astrophysics. I've embarked on a project and am seeking some guidance, insights, or even ways that I could look for possible collaboration on this ...
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Are liquids the rarest state of matter in the universe?
I was idly thinking what states of matter are common, which are rare overall. The commonest states of matter in the universe, by total mass, would be gases, solids (mostly as dust), and plasma (mostly ...
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What courses should one take for working towards Astronomy from an AI / Data Analysis perspective?
Note:- This is a suggestions seeking question
As a prospective student about to embark on pursuing the MEngg. in Applied AI program, I am eager to align my education with my passion for Astronomy. I ...
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Which coordinate system should one use for simulating a spacecraft trajectory to the moon? [closed]
Which coordinate system is most suited for this type of problem? ecliptic? equatorial?
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Trying to understand how to properly implement this equation to a healpix map
So i am working on reproducing a paper (Secrest, N. J., von Hausegger, S., Rameez, M., Mohayaee, R., Sarkar, S., & Colin, J. (2021). A test of the cosmological principle with quasars. The ...
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why does earth have speed?
I understand that Earth has a quite big speed such as it ends up around the orbit. The sun can't really attract it till the end due to Earth's speed and earth really can't escape due to gravity, hence,...
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Combining Systems Engineering and Cosmology/Astrophysics
in a nutshell, my undergrad was in Astrophysics, my master's is in Systems Engineering (SE), and I am currently completing my Ph.D. in SE focusing on deep learning applications towards engineering ...
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Why do cosmologists assume that inflation began shortly after the Big Bang, rather than at the exact start?
Somehow, I have never come across an explanation of why cosmologists claim that the alleged inflation of the very early universe occurred not at the Big Bang, but very shortly afterwards (~10^-36 to ...
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How does the gravitational wave strain from a rotating binary depend on the chirp mass, frequency and distance & what a short derivation looks like?
Our most familiar experience with wave propagation either from firsthand experience or in school comes from the phenomena of sound and light and radio electromagnetic propagation.
In air, we know that ...
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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 ...
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