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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Demonstration of comoving volume between 2 redshifts

I can't manage to demonstrate the relations $(1)$ and $(2)$ below, i.e the comoving volume between 2 redshifts. The comoving volume of a region covering a solid angle $\Omega$ between two redshifts $...
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How to change a strongly rooted scientific paradigm? [closed]

I bear witness that I have truly discovered that the earth does not revolve on its axis. That means that the heliocentric model although it explains many phenomena observable in the sky is not true. I ...
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What do we know about black hole and its existence? [duplicate]

Yesterday, I had an exchange with my colleague about a black hole. His theory was that black holes were merely an imaginary construction that is purported to have some mathematical meaning. Is what he ...
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Why couldn’t dark matter be from advanced technologies? [closed]

(Coming from a layman) Why couldn’t dark matter be the consequence of advanced technology? For many reasons I can imagine that the game theory for intelligent life is to eventually hide/ camouflage ...
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A search for IceCube events in the direction of ANITA neutrino candidates

In regards to the recent discover by ANITA of space-bound high energy Neutrinos, could this possibly be explained by atmospheric Beta Decay reactions producing these Neutrinos in between the IceCube ...
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Fluid description in the core of a white dwarf

I was just wondering whether we could use fluid-like description to deal with plasma in the core of white dwarfs. Now the core of these white dwarfs consists of degenerate electron gas and hence am I ...
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What happens at the atomic level when a black hole forms?

As I understand it, during a gravitational collapse, the star stops fusion and gravity overcomes the radiation pressure. At that point, there is a point in space where there is a lot of gravity in a ...
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215 views

Are the muon/tau neutrinos produced in the Sun? If not, then where?

I was reading about Solar Neutrinos, and apparently they are all Electron Neutrinos. However, there are two other types of neutrinos, the Muon and Tau Neutrinos. Does the Sun produce them? If not, ...
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Required Preconditions for Galactic Formation

In recent weeks, I have been working on building simulations to look at the formation of galaxies from dust clouds. It's a relatively crude simulation at this point as I needed a working model to ...
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105 views

Can quark stars form under an event horizon?

Past the Tolman–Oppenheimer–Volkoff limit, gravity overpowers neutron degeneracy pressure and neutron stars collapse, possibly to black holes. This essay by Graeme Heald suggests that a quark star ...
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How does the mass loss in a binary system affect the semi-major axis of the orbit?

It is common that during the stellar evolution one of the stars in a binary system would transfer mass into the the other, resulting in the increase of mass of one star and decrease of mass of the ...
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Black Hole accretion disk theory: Present status of research [closed]

Black Hole accretion disk theory is a major area of research in Relativistic Astrophysics at present. Since the publication of the classic papers on the topic by Shakura & Sunyaev (1973) and ...
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What is spectral redshift resolution of observationally detected damped Lyman Alpha clouds?

What is the spectral resolution, $\Delta z,$ when detecting damped Lyman alpha systems at different epochs, $z \sim 0-3,$ through current and/or future observational instruments? And is this redshift ...
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Is sunlight a continous spectrum?

In school, I have been tought that sunlight emits all wavelenghts of visible light. However, shouldn't also the sun have the footprints of its components? Shouldn't it's spectrum be similar to the ...
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How long from star collapse to supernova explosion?

According to some reports, Betelgeuse might "be ready to explode into a supernova". It's luminosity has decreased "considerably" in the recent weeks. If we consider the "stable period" as that when ...
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What elements do black holes expel into relativistic jets?

What does current research say about the elements that can be created in the accretion disc of a black hole, and does the Relativistic Jet contain any of those elements? Curious as to whether the ...
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Why does mass (gas) transfer between binary stars cause them to move apart?

Some binaries, like Algol binaries, move monotonically apart from each other as one steals gas from the other. Why? On a naive level, shouldn't friction and such cause the two stars to move (rotate?,...
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Luminosity-Surface Brightness relation in curved spacetime

Suppose we have two massive objects O and O' separated by a distance D. Spacetime around the objects O and O' are described by the metrics \begin{align} ds²&=-A(r)dt²+dr²/A(r)+r²d\Omega²\\ ds²&...
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Solar Oblateness: Understanding the force balance formula and solar radius in arcseconds

I have 2 questions regarding the following exam-style question and solution: Given a solar mass of $M_{\odot}=2.0 × 10^{30}\,$kg, a solar radius of $R_{\odot}=7.0 \times 10^8\,$m and a rotation ...
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Radiation efficiency of astrophysical objects using GR

The radiation efficiency $\epsilon$ of an object (for example a star or black hole) can be defined as the energy dissipated by some matter moving from infinity into a lower orbit divided by the total ...
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Evolution of red dwarf stars

While low mass stars (initial mass approximately $0.1 M_\odot$ to $0.8 M_\odot$) are quite numerous, their evolution seems to draw relatively little attention. The lower central density and ...
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1answer
81 views

Formula to Compute sigma8 for correction in non-linear regime

I need to apply a correction on $\sigma_{8}$ between linear and non-linear regime to keep it fixed (I make change the values of cosmological parameters at each iteration). I have to compute $\sigma_{8}...
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Scalar pressure of ideal gas: (non-)degenerate/(non-)relativistic behaviour

The scalar pressure of an ideal gas can be derived for different regimes: nd: non-degenerate ($E-\mu\gg k_BT$) ud: ultra-degenerate ($K_F\ll k_BT$) ($K_F$ the Fermi energy) nr: non-relativistic ($ E \...
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Why do later fusion stages in a star last shorter?

When most of the hydrogen in the core of a massive star has fused to form helium, the next fusion stages (helium, carbon, neon, oxygen, ...) produce less and less energy in a single fusion reaction. ...
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Lorentz invariance of the CMBR [duplicate]

From the Wikipedia entry on the CMBR dipole anisotropy (emphasis mine), From the CMB data it is seen that the earth appears to be moving at 368±2 km/s relative to the reference frame of the CMB (...
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Can I destroy a star faster by trapping it in a spherical mirror? [duplicate]

What would happen, if I were to trap the Sun in an almost perfectly reflective spherical mirror? I'm assuming this would accelerate the life of the sun and reduce the timescale required to turn it ...
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1answer
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Are there any patterns in the locations of pulsars in our universe?

Are there any particular places pulsars are distributed? If so, why? Any information to links and articles will also be appreciated. I just want to understand more about pulsars and if there are any ...
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What is the relationship between average pulsar amplitude and the frequency?

Hi my question is pretty much in the title when im referring to frequency im referring to the frequency of the pulses. I have plotted a graph frequency vs average pulse amplitude but i don't ...
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What is a cold black hole in astrophysics?

I found the word 'Cold Black hole' in some academic papers. I think it is concerned with thermodynamics of black hole but I don't know exactly what is cold black hole. Please help me to understand ...
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69 views

What is the minimum mass for gravity to form objects in a protoplanetary disk?

I understand that at smaller scales the strong, weak, and nuclear forces, and chemical bonds have more influence on the formation of objects than gravity. At what amount of mass does gravity become ...
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Lisa Pathfinder Mission - interpretation of results (frequency)

In the results of the space mission Lisa Pathfinder is on the xx axis the frequency value. Where does this frequency come from? Does it come from satellite orbit frequency or mass vibration?
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How to explore astrophysical fluid dynamics?

I'm a second year aerospace engineering undergrad student. I'm currently part of a project dealing with boundary layer flows on supersonic flights, and I find it to be really interesting. I wish to ...
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Why temperature of planets decreases as we move far from Sun?

Is there a friction in the space? If yes, then does that affect speed, wavelength and amplitude of an EM wave? And i also want to know, why temperature of planets decreases as we move far from Sun?
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Is there any significance to rotating frames theory (i.e, coriolis and centrifugal terms) in electromagnetic theory?

I attended a lecture on non-inertial frames of reference and fictitous forces in translating and rotating frames (in the case of rotating frames the relevant forces are Coriolis and centrifugal forces)...
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What's the energy of all the light/electromagnetic radiation in our galaxy?

I came upon this question while watching a pop-sci video on youtube about Dark Matter and thinking about all the things that could be contributing gravitational influence to a galaxy. From relativity ...
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Can the centre of a rocky planet ever freeze?

When a rocky planet like the Earth or Mars forms the gravitational potential energy is converted to heat energy within the planet. Planets lose heat energy over time by emitting radiation. But is ...
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Pressure (gravitational) applied by a hollow, uniform, spherical shell on an object inside it

1) It's a well-known result that the net force inside a hollow, uniform spherical shell is zero at all points. However, for a spherical shell with finite mass inside of it, we say that the mass ...
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Pressure inside a Hollow (uniform) Sphere

I understand that Gauss' Law (or manual integration) yields that the net force inside a hollow, uniform spherical shell is zero at all points. However, for a spherical shell with finite mass inside ...
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Roche lobes in binary star systems

While studying mass transfer in binary star systems, I came across the concept of Roche lobes and the role of the inner Lagrangian point $L_1$, as shown in the adjoining figure. However, I am having ...
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Friedman equation with non-negligible neutrino masses

I have heard that the Friedman equation (for lambda-cdm) with significant neutrino masses is modified from its simpler form (sum over various densities of c.c., curvature, matter and radiation) to a ...
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Non-flat Galaxy rotation curves?

The galaxy rotation curve is stated as being constant, hinting towards the presence of dark matter. But few galaxy rotation curves are not constant but it keeps rising (an example shown in image), can ...
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Heavy elements creation [duplicate]

Would elements heavier than iron not be extremely rare if only created by supernovae? I believe all elements above hydrogen are created in the star's corona. Hydrogen fusion is not possible in star's ...
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body vs electron spaghettification

What would cause an extended object (like a person) to be subjected to “spaghettification” when falling into a black hole, even though that would not happen to a point object (like an electron)?
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Researching Black Hole Spin/Mass

I'm a high school student investigating how one can predict the mass and spin of the product of a binary black hole system. I'm fluent in Calculus (Single Variable), Number Theory, and Graph Theory, ...
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Misunderstanding of how the Sun losing mass makes the Earth orbit increases in size

The radius of the Earth orbit increases by about 15 cm per year. One of the main argument found online to explain this is the fact that the gravitational pull of the Sun on the Earth diminishes over ...
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Useful resources and softwares for computational astrophysics

I am recently working on computational astrophysics. My research is mainly focused on accretion processes around compact objects (black holes & neutron stars), radiative transfer and modelling of ...
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How big is the role of black hole spin in forming its mass?

Excuse me if i'm saying something weird, but as far as i know moving faster means increasing mass according to relativity theory, right? If you make some star spin really really fast throwing ...
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Theoretical lower limit to the density of a planet

If a celestial body is too dense, hydrogen fusion will ignite and it will become a star. As such, there is an upper limit on the density a planet can have. But is there a lower bound on the density ...
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Importance of high order separation in Echelle spectrometers?

I've been reading on the subject and constantly find that in astronomy Echelle spectrometers are used. I've also found that greater order separation favors long slit spectroscopy. Why is this?