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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Finding an out of stock astrophysics solution manual [closed]

Where can I get the Solution Manual to "Astrophysics in a Nutshell " by Dan Maoz pdf? (The Amazon hardcover version is out stock and I couldn't find it on chegg as well)
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Textbooks on cosmology *after* recombination

I am a theoretical physicist and I have a reasonable understanding of the early universe, inflation, FLRW metric, leptogenesis, baryogenesis, perturbations, the works (mainly in the style of the ...
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Nuclear reactions in stars: tunneling?

Energy production in stars occurs mainly when a nucleus absorbs a proton or fuses with another nucleus. Some examples: (i) $\rm{p}(\rm{p},\rm{e}^+\nu)\rm{d}~$ and $~\rm{d}(\rm{p},\gamma)^3\rm{He}~$ ...
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Is Jupiter really protecting us from collisions with objects?

Many documentaries I see on the Solar System or the planets or the threat of collisions with meteorites talk about how lucky we are to have Jupiter, with its immense gravity attracting asteroids to it ...
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Physical relation between adiabatic constant $\gamma$ and polytropic index $n$

I am study about stellar model of stars by using polytropic equation of state $$P=k\rho ^{\gamma}$$ or $$P=k\rho ^{1+1/n }.$$ I studied that different values of polytropic index $n$ describes ...
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Physics of black holes [duplicate]

does anyone know good books and/or other sources of information regarding black hole mathematics/physics? Currently I'm reading the black hole wars by Leonard Susskind; it seems to be a collection of ...
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Angular size of the largest region in causal contact at the moment of recombination

I want to calculate the angular size of the largest region in causal contact at the moment of recombination (z = 1100) to our universe, so we have: $H_0 = 68$ (km/s)/Mpc, $\Omega_{m,0} = 0.31$, $\...
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Is this how a sphere warms up?

I have been trying to solve the heat equation for a uniform sphere. My setup: sphere has an initial temperature distribution, and the surface is kept at constant temperature. I am interested in how ...
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How fast did the interior of Venus warm up?

Context: The atmosphere of Venus wasn't always as warm as now: a few hundred million years ago it was much more habitable. I am interested in how fast the interior of the planet warmed up, after it's ...
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What is a good research question for a physics extended essay? [closed]

I'm an IBDP student, and I need to work on a research question for an extended essay. An extended essay is an academic research paper written in 11th and 12th grade. I can either do a paper on a ...
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Does Hubble's constant apply to galaxies that are blue-shifted/ moving towards us? Another question

Does Hubble's constant apply to galaxies that are moving towards Earth with a velocity and does Hubble's constant also able to different systems such as binary stars, stars in another galaxies or ...
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Why is the isotope Nitrogen-14 formed preferentially in CNO-cycle stars? As opposed to N-15?

Most of the universe's nitrogen is formed in larger, main sequence stars using the CNO Cycle, right? But I cannot find a good, specific explanation as to why N-14, with odd numbers of both neutrons ...
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Death of Stars and Red Giants [duplicate]

As a matter of fact, I was learning stellar astrophysics where I couldn't understand the chain of events at the time of death of stars, Once the hydrogen fuel core is exhausted, the stars start ...
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Gravitational Collapse: Kerr solution is a vacuum solution but not for any rotating body?

Consider then the following reasoning: Schwarzschild Metric describes the spacetime of a black hole. A gravitational collapse is a mechanism to produce Schwarzschild Black Holes. Conversely, a ...
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What is the amount of mass ($\rm kg$) that the Sun loses daily in the irradiation form?

I had difficulties to post my question because the system asks me to detail my need more. Is it necessary? Doesn't my question make sense? There is no need to answer, I just want to know if there is ...
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What if Jupiter or the Sun was made of rock, like Earth and Mars, rather than gas?

Jupiter is a "gas giant". If it was (significantly) bigger the pressure from gravitation would ignite a fusion process and it would become a star, which is basically what happened to the sun....
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What could a satellite orbiting M87 at the innermost stable circular orbit see?

If I understand correctly, the radius of the M87 event horizon is approximately 19 billion km. I used an escape velocity calculator as a sanity check, entering 1.28E40 kg and 1.9E10 km and the ...
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Neutron star lifetime and density relation

It is very interesting to note that Pauli's exclusion principle from QM is sustaining a classical object such as a neutron star, black hole etc. all the more reason to look for a unified theory of ...
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Do bolometers measure all posible wavelengths of EM radiation? Is this even possible?

What is the closest thing we have to a 'black-body' bolometer? What are the best absorptive bolometers made of?
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How can R136c be so large?

I have read the other question (How can a Population III star be so massive)... but it does not answer my question. R136c Is a Wolfe-Rayet star. It is 230 the mass of our sun. My question is this: ...
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35 views

Why are there fewer lines on the absorption spectrum than on the emission spectrum for some gases?

I don't know if this is right, but I think that it is because: when the gas is heated, the electrons get 'excited' and move up to an energy level (lets say an electron moves up 4 energy levels). ...
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1answer
14 views

Pressure stabilisation of radionuclei

Looking at explanations of neutron stars, the neutrons towards the center of the star are stabilised by the enormous pressure, and so don't undergo nuclear decay. I am wondering if this is possible ...
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Abundance Ratios from Explosive Nucleosynthesis Models

I am having trouble deriving the abundance ratios for the ejecta products of a given supernova explosion model. From the explosion models, we are given the mass of 3 isotopes of every element produced ...
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Derivation of Mattig's Formula

Mattig's formula for any k: How to derive this equation without using General Relativity?
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Steady-State Accretion Disk with Resistivity

I'm trying to study the basics of Resistive RMHD in the environment of an accretion disc. I have found some great papers (Ferreira, J.; Pelletier, G) but are focused more on jet extractio. Can you ...
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What's the redshift of a return signal in a flat universe between two observers?

I'm trying to determine the redshift observed for a light signal between 2 observers (let's call them observers one and two) in a flat matter-dominated universe. Observer one sends a signal ($t_1$) at ...
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Earth doesn't have seafloor craters. Does it mean water has been on Earth since long time before in the past?

Is it true that Earth didn't get its water by cometes impacts as there are no subocean craters so it seems water acted as a comete bumper long before in the past?
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How do you get the total energy of an event for a detector array?

THE SET-UP: The air-shower detector array made out of six detectors. The detectors are composed of a scintillator and a SiPM (Sillicon Photomultiplier) each. Depending on the shower size, one or more ...
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Do “almost black holes” exist?

The only things I read about so far in astrophysics are either black holes, developing black holes or not black holes at all. So I am wondering, is it physically possible to have an object that is ...
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How do astronomers detect the spin of the black holes?

There are various theoretical models for accretion disks and relativistic jets from black holes that considers the black hole to be either rotating (Kerr geometry) or non-rotating (Schwarzschild ...
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Cross correlations between 2 sensors - Approximation of a 2D + 3D synthesis

I am interested, in the context of my work, in the cross correlations between a spectroscopic probe (which gives a 3D distribution of galaxies with redshifts, which is also called spectroscopic Galaxy ...
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How to derive the hydrostatic equilibrium equation from the variational principle?

I was reading the book "Advanced Stellar Astrophysics" (William K. Rose, 1998) and I came across a different approach to deriving the hydrostatic equilibrium equation. First he defined the ...
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Calculating pressure and flux tensors in radiative astrophysics

I need to calculate the components of the radiative flux tensor and the pressure tensor, but I am having a little trouble figuring out what the integral should be. The flux is defined as $$F_v = 4{\pi}...
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How does a solar wind plasmoid split when it touches the magnetosphere?

I want to try to render (computer graphics) auroras in a physical manner as realistic and realizable as possible. I'm aware that the phenomenon hasn't been completly explained yet (as far as my own ...
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Why Sun's coronal belt is more stable at Sun's equator?

As the Sun's coronal belt is made up of protons and electrons constantly scattered by photosphere's sunlight and as these particles are forced to do loops due to Sun's magnetic field is it possible ...
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Empirical relation between O[III] and H$\alpha$ line fluxes

I have the H$\alpha$ line flux ($L_{H\alpha}$) of an extragalactic source. To calculate the bolometric luminosity, is there an empirical relation between $L_{H\alpha}$ and $L_{O[III]}$, akin to $L_{O[...
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Why does the spectrum of Sun follow a black-body distribution curve?

Black-body radiation, as I understand it, is radiation in thermal equilibrium at a fixed temperature with a cavity. The spectrum of such radiation follows the famous black-body distribution curve. But ...
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Does the Sun have enough gravitation to bind its hydrogen/helium plasma?

"Does the Sun have enough gravitation to bind its hydrogen/helium plasma?" So my question arises from the fact that high energy (or high temperature in other words) hydrogen or helium gas ...
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What are the charges of all planets in our solar system? [duplicate]

What are the charges of all the planets in our solar system and what are the charges of whole universe, solar system and milky way etc..
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Are there papers or experiments that point to non-fusion sources of solar neutrinos?

I've read that nuclear fusion is what generates such large quantities of solar neutrinos. Also saw that it was recently experimentally confirmed that two types/energies of neutrinos are generated in ...
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What happens if a magnetar collapses into a black hole?

Assume there is a neutron star with a magnetic field and no net electrical charge. What happens to the magnetic field if it gains some mass and collapses into a black hole?
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How long could the Sun power the Earth?

With the energy emitted by the sun in 1 second, how long could everyone household on earth be powered? Currently we obviously can't harvest 100% of the sun's energy emissions.
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Pair-instability supernovae: a thermodynamic perspective

The discovery of a black-hole pair with "forbidden" masses has gotten me trying to understand pair-instability supernovae. A well-crafted sentence from a recent paper gives the explanation ...
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Are there examples of dark matter at intra-galactic scales?

In articles I've read, evidence of dark matter (rotation of galaxies / gravitational lensing / galaxy collisions etc) is presented at galactic scales. Are there examples of dark matter at smaller ...
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How does the Sun generate its energy?

We all know that the sun generates its energy from nuclear fusion in the core. The electromagnetic radiation produced slowly travels upwards, while constantly being absorbed and re-emitted by the ...
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Can Hawking radiation be observed from the radiation (spectrum) of M87*?

Using $M87^*$ data from EHT observation (mass, temp of the surrounding accreting disk) and approximating area of EH by euclidean geometry $4\pi r^2)$, error comes around of order one or two. One gets ...
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Is the maximum spin-frecuency of a neutron star related with the stiffness of an equation of state?

I know that stiffer EoS gives bigger stars and stars with bigger maximum masses. The problem is that I'm computing the maximum spin-frecueny of a neutron star for two EoS, and I'm getting higher $\...
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Why is Stephenson 2-18 so large?

How does a star as large as Stephenson 2-18 get this big? It is 2500 times larger than the sun. Did it start out as a large star with a lot of gas left over that gradually consumed the gas growing ...
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What is the effect of radius in a planet's steady state temperature?

Let's say there are two planets, without an atmosphere, sharing orbit and equal in every way except their size: planet 1 is 10x larger than planet 2. Heat into the planet $Q_{in}$ from radiation is ...
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Equations for developing a hypothetical Solar System

I am currently going down the rabbit hole of writing a story but I would like it to be set in a universe which is believable. Therefore I am trying to create a hypothetical solar system in which the ...

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