Questions tagged [astrophysics]
The application of physical theory to celestial systems such as stars, planets, galaxies, supernovae, and black holes. Astrophysics proper is concerned with explaining phenomena more so than making observations, the latter falling under the purview of astronomy.
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Sling-Shooting Around a Star to Catch a Solar Flare
How much thrust could a solar sail receive from sling shooting around the Sun and riding the wave of a solar flare during the escape?
I found this link https://ww4.fmovies.co/film/the-ark-season-1-...
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How to identify the composition of sun if it is treated like a blackbody? [duplicate]
The sun is usually assumed to be approximately very close to a blackbody, but using spectroscopy it is concluded that the sun is made up of Hydrogen and Helium because the lines corresponding to those ...
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Relic density and cross section
Is it possible that our annihilation cross section and relic density decreases if we add more dark matter particles having same mass the same portal couplings in the model ? if yes, what is the ...
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Is the existence of hydrostatic relativistic objects a coincidence or inevitable?
Neutron stars are unique in the universe because their sizes are just slightly bigger than their Schwarzschild radii. Because their sizes are comparable with their Schwarzschild radii, the nonlinear ...
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Are Superconducting deflections of asteroids possible?
Example problem:
A 1m radius deposit of Metallic H²S(Sulfur Hydride) is trapped inside of a 50km radius Asteroid weighing approximately 3.75×10¹⁷Kg; it is under constant pressure of 95GPa; it is ...
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Can we distinguish between gravity and electrostatic forces interacting on celestial bodies?
The orbit of one celestial body around another is thought to be caused by gravity alone. However, could part of the force determining the orbit (at least in theory) be caused by a difference in the ...
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Dwarf galaxy rotation speed around Andromeda/Mily way
We know that the rotation speed of stars around the center of a galaxy is roughly flat.
But how fast does the dwarf galaxy rotate around the bigger galaxy, say andromeda or milky way?
Do they also ...
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Question on the relation between the Hubble constant and the absolute magnitude of Type Ia supernovae
I would like to ask a question about the relation between the Hubble constant and the absolute magnitude of supernovae
I have read that supernovae alone cannot fix $H_0$ and that there is a ...
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Quantum efficiency and relative response of a photodetector
by looking at those two graphs from the same CMOS sensor (Sony IMX 533), one monochromatic and one with a colour filter array (CFA), I was wondering why the monochrome sensor is expressed as absolute ...
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Meaning of Left-Right Arrow in a Fitting Formula [duplicate]
I initially posted this question on Astronomy Stack Exchange but the site seemed rather inactive so I will try to ask it again on Physics, hopefully it doesn't go against any rules.
I was reading this ...
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Nuclear level densities and neutron stars
My current PhD. project involves working with nuclear level densities (NLDs). However, I am more interested in the applications of NLDs to astrophysics. I know they are important to in calculations of ...
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Is the temperature of the hottest star's core known?
WR 102 is believed to be the hottest star in the observable universe, whose surface temperature is $210,000 ^\circ K$. But the related wikipedia entry does not say anything about the temperature of ...
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In a non-rotating sphere of fluid heated from the centre, what does the flow look like?
Consider a perfect sphere of fluid which is not rotating, is under the influence of its own gravity only, and is heated from the centre. What does the flow of fluid in the body look like?
In the ...
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Sorts of relativistic effect around black holes [closed]
There are many effects around black holes. In particular it is possible to study the motion of geodesics, calculate tidal tensors, lense-thirring effetcs and so on.
So, beyond tidal effects, geodesic ...
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The energy density of E&M waves in intergalactic space
Let's imagine that we placed a cube with a side of 1 meter in the intergalactic space. How much energy in the form of electromagnetic waves will pass through a unit volume from all sources of ...
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How does Viscosity of the Sun varies as we go from core to the convective zone?
How does Viscosity of the Sun varies with its radius?
For. eg, Here is the graph of the Density of the sun v/s radius. I am looking for the Viscosity v/s radius plot.
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Literature about robust standard errors in astrophysics?
Can you help me find any literature about robust standard errors in astrophysics? I found something about heteroscedasticity but they all use different methods rather then Huber-White estimators.
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Recombination of protons in solar wind
All accounts of solar wind I have seen (I am no expert in the topic), seem to refer to it being everywhere a plasma (mainly composed of protons/electrons). For example, I have seen statements about ...
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Axion vs. WIMP / Is Axion a WIMP?
What is the difference between an Axion and a WIMP?
A WIMP is just defined as a class of particles interacting via gravity and potentially via weak interaction (or a new force that is even weaker than ...
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What are astrocentric co-ordinates?
A program I am using requires the ecliptic astrocentric cartesian coordinates of the Earth and the Sun in AU however I have never come across these co-ordinates before and the internet doesn't provide ...
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How long will Brown Dwarfs live?
Brown Dwarfs are a technical star because of their masses. If Red Dwarfs live for 10 trillion years, then how long could Brown Dwarfs live?
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Does the Sun increase entropy?
The Sun generates heat via fusion. The heat from this reaction gets distributed around the solar system and beyond. This process of spewing heat and radiation all over the place doesn't immediately ...
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Observed flux of a non-spherical object
I recently had an exercise for which I had to find the observed flux of an annulus (accretion disc of a black hole). With the assumption that the annulus behaves as a perfect black body, the provided ...
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Is a planetary collision cascade possible?
It would seem to go against common sense that it would be possible for a small rocket to destroy a solar system, but do the laws of physics actually forbid it? Suppose a rocket were to hit an ...
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Dark energy, potential energy and energy conservation...?
The universe has an accelerated expansion (due to dark energy, according to the standard cosmology model).
There are some papers (like this one: https://arxiv.org/abs/astro-ph/0507195) that mention ...
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Biermann Mechanism [closed]
Biermann mechanism says that due to different masses of electrons and protons, the motion of former leads to the latter. This effect produces non-zero circular currents which induce vertical magnetic ...
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How exactly does the Moon stabilizes Earth axial tilt?
There are many references regarding the Moon stabilizing the tilt of the Earth's rotational axis. I'd like to see some support for that claim, more than non-sequitur handwaving "Moon causes tides,...
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Identifying the Milky Way uniquely [closed]
Let’s suppose you wanted to elegantly represent the Milky Way in a minimalist fashion in a way that would make sense a billion years hence (ie let’s set aside the damage wrought by colliding with ...
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Is sun orbiting the center of the Milky Way? [closed]
Are all the celestial bodies in our galaxy (along with the Sun) orbiting the center of the Milky Way Galaxy?
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Why is the common envelope ejected in some accretor-donor systems?
As an example, let us consider a binary system of a neutron star and an evolved star (e.g. red giant) that has expanded, filled its roche lobe, and started the mass transfer onto the neutron star.
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Star collapses to a singularity or is collapsing into singularity?
This has bothered me for a while now, however I barely have a vocabulary to ask it. Please let me try.
When a star, at the end of its life starts to collapse into the black hole, all the atomic forces ...
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Emissions in the gamma ray frequency from gamma ray burst [closed]
Since almost all the emissions detected from gamma-ray burst are from its afterglow which are not in the gamma-ray frequency. Is the afterglow emission frequency lower than gamma-ray frequency ? I ...
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Kinetic energy and collisions in cosmology? [duplicate]
Objects in space time can move due to the expansion of spacetime itself (where objects that are sufficiently far apart would recede from each other due to the Hubble flow) and peculiar motions (which ...
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Can black holes have colour charge? [duplicate]
Does the no hair's theorem take into account all the elementary particles and forces, and in particular can a black hole have color charge?
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Time dilation is caused due to [duplicate]
Does time dialtion is caused due to the decrease in temporal velocity of an object
i don't understand temporal velocity clearly
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Blueshift caused by dark energy?
Galaxies that are sufficiently far away from our point of view are receding from us due to the accelerated expansion of the universe (supposedly caused by dark energy) and therefore their light is ...
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What is the core temperature of neutron star as a function of time?
I wish to know about the temperature of the bulk (not just the surface) of a neutron star. I am especially interested in the highest temperature part which I assume is the core, but would want to know ...
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Will interstellar helium condense to a liquid as space expands and cools?
Intergalactic space is 2.7K (https://en.wikipedia.org/wiki/Outer_space) Interstellar space is a little warmer. My understanding is that these will decrease over time.
The phase diagrams of helium I ...
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Why is a primordial black hole's mass of the same order as the horizon mass in the early universe?
I am reading a paper on primordial black holes (PBHs), and it says that PBHs should form during the first second of the universe with masses of the same order of magnitude as the horizon mass.
I ...
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Introductory books on astrophysics [duplicate]
I'm looking to get deeper into astrophysics and physics in general. I already know physics from the internet (YouTube physics channels, etc.). I don't have a lot of mathematical skills. I know some ...
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Is the Sun considered to be a black body as a whole or it is only the photosphere which is a black body?
I am having some difficulties understating how fusion inside the Sun is connected to the Sun being a blackbody. How do the photons transfer to the photosphere? Is the amount of transferred energy less ...
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Why doesn't a black body absorb its own radiation?
If black bodies absorb all the radiation and emit radiation by themselves, why don't they absorb their own emitted radiation? We shouldn't see the sun for example, since it's a black body.
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Does the rate of expansion of the universe depend on the mass or size of the galaxies?
Does the rate of expansion of the universe depend on the mass or size of the galaxies? How constant dark energy density affect the massive/lighter galaxies?
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Has anybody measured the Schwarzschild radius of a black hole and does the radius equal the radius predicted from the mass?
Have schwarzschild radii been measured from quasars or lensing black holes of known mass?
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How much pressure (force) is needed to turn something into a black hole? [closed]
I just curious to know "how much pressure/force needed to crush anything that it will get the schwarzschild radius $R=GM/c^2$.
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Why is a star unstable if it's adiabatic exponents are less than 4/3?
In "Introduction to Stellar Structure" by Walter J. Maciel at page 76 it is said that for a partially ionized non degenerate hydrogen gas, the star is unstable if the adiabatic exponents are ...
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Other Hubble spheres with no Lorentz symmetry?
Perhaps this is a stupid question but, if Lorentz symmetry is not global but rather local, wouldn't that mean that is possible that other Hubble spheres outside our observable universe could have ...
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Kinetic energy being transformed into other types of energy in cosmology?
Spacetime expands at an accelerated rate and the particles with movement associated to this expansion are said to be coupled to the Hubble flow. In many papers that I've read, objects coupled to the ...
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Star convection gradient dependencies
In star convection you can work with radiative and adiabatic temperature gradients, that for example the radiative one can be defined as,
$$\nabla_{rad}=\frac{3\kappa L P}{16 \pi a c G m T^4}$$
This ...
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Influence of external gravitational fields on the volume of a part of the black hole event horizon
FIRST QUESTION: In the event that a smaller black hole orbiting a larger black hole in an elongated elliptical orbit reaches the so-called perihelion of its trajectory, can it temporarily change the ...
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