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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Adiabatic equation of state for a star

I am a little confused. To describe stars the adiabatic equation is often used: P = k$\rho^{\gamma}$. For a monatomic gas, the following holds: $\gamma = \frac{5}{3}$. However, since the sun is not ...
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Why the megaastrophysical objects do not collapse due to their gravitational selfattraction?

At the largest scale in the universe exist formations called filaments which form something like a spider web along the whole universe. But they seem to be quite static. So my question is about the ...
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What's the lifespan of Deuterium and Helium-3 in the Sun?

What's the lifespan of Deuterium and Helium-3 in the sun? How long on average, the Deuterium and Helium-3 atoms last in the Sun's core?
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Could Dark Matter Be Fully or Partially Explained by Gravitational Waves?

This is something I have wondered for a long time and cannot see why it is not a possible solution. Basically, any motion of matter (Mass may be a more accurate description here) through space time ...
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Do supernovas vaporize the local space rocks 10 Pluto distances away?

In a follow-up to this question, What would it be like to watch an average space rock / ice comet at 1-20 Pluto distances from a supernova of $10^{44}$ joules? At what proximity would they become ...
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What kind of electric field would be needed to get a static discharge between two bodies inside vacuum space?

I know a perfect vacuum is also the perfect dielectric but I'm wondering if lightening between two bodies in outer space is possible? In other words, since vacuum is not perfect in outer space but ...
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What happens to the matter already at the very center of the star when it turns to a black hole?

I was wondering whether when an object collapses into a black hole, the matter in the position $r=0$, instantly becomes part of the singularity, or does it take time to fall into the singularity, and ...
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Why do elliptical galaxies not have large proportion of blue stars?

In an article it was given that elliptical galaxies are also formed when a spiral galaxy experiences continuous star burst thus depleting it's gas. So if this is correct than why do elliptical ...
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Why are sunspots cooler than the other regions?

The Sunspots appear darker than the other regions because they are cooler; and I know that according the Babcock model, the Sunspots are places where the tangled magnetic fields burst out through the ...
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Winds or waves in specific conditions?

Winds are mainly produced by differences in temperature of the atmosphere and waves are mainly produced by winds. However, could a rogue planet (without orbiting any star and with a cold core so no ...
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Is there other observational evidence apart from CMB that the universe is homogeneous and isotropic?

When I search about the homogeneity and isotropy of the universe, I always find that the CMB and the smoothness of temperature are good observational evidence to suppose that our universe is ...
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How to ask a question on StackExchange about a poorly conceptualized physical phenomenon to avoid being closed by the administrator? [migrated]

Questions that are not clearly described are quickly closed down by admin, who are almost unlikely to help the asker clarify their confusion by asking suggestive questions such as "do you mean...&...
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Justification for proportionality in Hubble's law

I just read about the Hubble's law which states that the speed $v$ (related to a point $A$, let's say the center of Earth) of a galaxy and its distance D (to the same point $A$) are proportional: $v = ...
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Does Shapiro Time Delay Impact our Estimates for the Age of Celestial Objects?

Per my previous question Can Shapiro Time Delay cause light in a vacuum to go faster than c as viewed from a remote reference frame? The speed of light can be observed as greater than c from our ...
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How does a neutron star "reheat" itself by ohmic dissipation of its magnetic field?

@ProfRob's answer to Neutron star accurate visualization ends with: ...How their temperatures evolve after this is highly uncertain and none have been observed. The problem is that neutron stars have ...
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Neutron star accurate visualization

Has any simulation been done to produce an accurate visualization of a neutron star, as seen from an observer at distances on the order of 1 AU? (Edit: I suppose instead of 1 AU I mean "distance ...
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Light curve of supernove: rise of LC

I have a question concerning the LC of SNe. First of all we have a huge energy deposited into the core of a star ad as a result we have a huge shockwave that develops, that heats and accelerates the ...
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What process led to the era of Reionization in the early Universe?

Reionization was the second major phase transition in the early Universe. At the wiki article for the epoch of Reionization in the early Universe, it states: The second phase change [i.e., ...
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Can strong magnetic fields exist in a large scale?

there. Can strong magnetic fields with strength about $1$ T to $10^{3}$ T exist in a large scale, e.g., about several light years? I searched on Google Scholar, but I could not find related papers.
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Why are most ring galaxies present in the field instead of rich galaxy clusters?

I was reading an article in which it said that mostly ring galaxies are present in the ‘field’ instead of rich galaxy clusters. Can anyone explain why is it so? I read about it's formation and i ...
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Galaxy rotation curve and galaxy mass

Is there a relation between the saturation velocity of the galaxy rotation curve and the luminous mass of the galaxy? To clarify the question, if one were to plot a scatter plot with the x-axis as the ...
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Too many low redshift galaxies in NED database

When using the NED database I found there are too many galaxies with very low redshift (Near zero). I used NEDs search by parameters function to find all galaxies within Z=0 to Z=.03 redshift. I did ...
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Does the RA and DEC of the sun change with time?

I'm almost certainly misreading this, but it's said that "one of the great advantages of the equatorial system is that the RA and Dec of a star do not change with time, at least over short ...
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What does the no-hair theorem state about the entropy of black holes?

So does the no hair theorem say that all classical black holes will have zero entropy? If yes, why?
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What is the dimension of cosmological constant $\Lambda$

I came across two forms of the Friedmann equation. Those are as follows: $$H^2=\frac{8\pi G \epsilon}{3c^2}-\frac{\kappa c^2}{R_{0}^2 a^2}+\frac{\Lambda}{3}\tag{1}$$ $$H^2=\frac{8\pi G \rho}{3}-\frac{...
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Showing that flux fluctuation is $q^2 P_n(q)/2\pi$

In the context of spectral analysis of a sufficiently small section of the sky, 1 states that the flux fluctuation is given by $q^2 P_n(q)/2\pi$ on the angular scale of wavelength $2\pi/q$, where $P_n(...
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Astropy Package - Defining new dark energy parametrization

I was looking through astropy, and I wonder is it possible to define a new dark energy parametrization instead of using the pre-defined ones..? I couldn't see the reference but maybe I missed it. ...
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Speed of sound in a gas (for adiabatic perturbations in cosmology)

In the book "Introduction to Cosmology" by Barbara Ryden, equation 4.57 gives the sound speed for adiabatic perturbations in a gas with pressure P and energy density $\epsilon$. The equation ...
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Can we measure the black-body radiation/ electromagnetic radiation that pass through some point P in space?

I was wondering if we can measure the black-body/electromagnetic radiation energy of a point in space without actually knowing the source of this energy. Let us say 2 stars emit black-body radiation/...
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Are there primordial populations of neutron stars and white dwarfs?

There is a well-known prediction that density fluctuations in the first moments of the Big Bang produced primordial black holes. Black holes from stellar collapse have their masses constrained by ...
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What is ohmic decay and why does it happen in magnetized celestial bodies like stars and pulsars?

I've seen term "ohmic decay" mentioned in several papers (example) regarding the decay of magnetic fields in celestial bodies like planets, stars, and pulsars, but I can't seem find a clear ...
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How is perspective compensated when analyzing the rotation of distant galaxies?

I can't find any information about that, but I always wondered: When analyzing a distant galaxy, how is the perspective taken in account when analyzing both its movement and the apparent density ...
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How to obtain exoplanets transmission spectra from JWST's NIRISS data of WASP96?

I was having a look at JWST's NIRISS data of WASP96 (specifically at the x1dints fits file which should be already calibrated). From this, I would like to obtain a result in a fashion similar to the ...
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On average, how often does any given hydrogen nucleus run into another hydrogen nucleus in the Sun?

I think there is a misprint in an article. I will include the link if you don't mind and cut paste the sentence that I think is a misprint. Here is the link https://www.abc.net.au/science/articles/...
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Why is the scientific community, and especially the astrophysicists, so skeptical about sterile neutrinos?

As rob pointed out in a comment in my previous question : "There were hints about sterile or missing neutrinos in LSND, in the low-statistics region of MiniBoone, and in a number of other ...
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Is the total gravitational energy in the sun greater than the energy that is produced by the sum total of the nuclear fusion contained therein?

I think this is off topic, maybe an astronomy question. Unlike a chemical chain reaction or a fission chain reaction I believe fusion cannot sustain inself. Is more energy going out than is going in ...
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If barycenter true, then how general relativity explain it?

I found that earth actually doesn't orbit sun. Sun and other planets both orbit the barycenter(Their central of mass).Then, what about Einstein's theory ? That heavy mass(sun) wrap space-time, thus ...
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Can gravitational effects from past matter that you're looking at lightyears away produce an incorrect image of it? [closed]

Can gravitational effects from past matter that you're looking at lightyears away produce an incorrect image of it? During the period that light from distant matter is travelling back to earth, can ...
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Will the trajectory of a body moving straight towards a rotating BH differ if space just rotates around or if space spiralls into the BH?

Will the trajectory of a body moving straight towards a rotating BH differ if space just rotates around or if space spiralls into the BH? Can this difference be clearly measured? Also as a very dense ...
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How big is the core of a supergiant star before it collapses into a neutron star?

What is the typical mass and density of the core of a supergiant star before it collapses into a neutron star?
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Is HD1 Galaxy a potential Big Bang theory killer?

I have heard some first explanations of why the farthest ever galaxy discovered about 13.27 Bly away the HD1 appears so UV active and about the population III stars inside this galaxy made only from ...
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Can we apply Maxwell-Boltzmann distribution law on non-identical particles? Can we apply it on astro-physical systems?

I was wondering whether we can apply Maxwell-Boltzmann distribution law on particles with different masses and composition. Also, is it possible to apply it on an astro-physical systems like planets ...
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Would the Earth's magnetosphere be more effective against the Sun's solar wind if the planet's rotation was faster?

As far as I understand it, the Earth's magnetic field rotates around the planet's axis at the same rotational velocity as the planet's rotational velocity around its axis. From what I understand about ...
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How can the Cosmic Neutrino Background (CνB) have a temperature? How can any neutrino have a 'temperature'?

The word temperature usually refers to the average velocity of massive particles, correct? And the Cosmic Microwave Background (CMB) has a 'temperature' based on the temperature of a 'black body' that ...
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Is a black hole a single particle or a bunch of particles that binds together?

We know that in a neutron star all electrons and protons combine together and make neutrons because of the gravitational pulls. We also know that a black hole is much denser than a neutron star, we ...
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Is there a maximum mass limit for black holes?

We all knows that neutron star and a black hole is a final end stage of a giant stars, and neutron stars can also become a black hole, we also knows that minimum mass limit for stars to become a ...
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Can hot planets host water?

Boiling point of water increases with pressure. If so, can a planet with the right atmospheric pressure contain oceans (made of water) irrespective of its temperature?
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Where were the first galaxies formed in our observable Universe, at the center or at its outskirts?

After inflation where were the first galaxies formed? At the center (our home position) of our observable Universe or at its outside rim? I know that for the case of a galaxy the standard view is that ...
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What is the significance of a constant, $C$ in a damped cosine function? [closed]

I've used to fit some scattered points by an equation of damped cosine with a constant function ($(A\cos({kx})+C)e^{-Bx}$) and that equation fits better than only a damped cosine $A\cos({kx})e^{-Bx}$, ...
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Inside the Photon sphere of a black hole

A photon sphere is defined as the innermost orbit in which the gravitational force of the compact object causes light to orbit it. The event horizon is the boundary at which the escape velocity is the ...

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