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Questions tagged [white-dwarfs]

The final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole.

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Is Earth's iron core kind of like a white dwarf?

Because Earth's iron core has iron atoms not bonded to one another but in a lattice where there is a sea of electrons and there are ionized iron atoms holding back from gravitational collapse of the ...
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Mass formation of a neutron star Vs White dwarf

I have been researching the different outcomes of a star's death. I understand that the main factor is the star's mass at the end of its life, along with others such as its metallicity. Well, the ...
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Luminosity and absolute magnitude relationship

Context : an exercise gives the temperature, mass, distance and apparent magnitude of Sirius B and asks to calculate its density. One key step of the calculation is to get the luminosity from the ...
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Massive star evolution leading to white dwarf?

Is it possible that a star with an initial mass greater than $12 M_\odot$ loses so much mass in the giant phase that it eventually becomes a white dwarf? If it is possible, what constellation or ...
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Does the wave function of localized s-orbitals radius reduce under extreme solid-state pressures prior to degeneracy?

Under extreme conditions not found in nature, say low temperature solids that are under extreme pressures* prior to collapse into degenerate matter states, does a localized s-orbital radius reduce ...
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Paradox about white dwarfs and ionization

I am facing a dilemma. The fact that matter is ionized allows ions and electrons to be much closer together than they are in atoms (Bohr radius $a = 0.5 \cdot 10^{− 10} \mathrm{m}$), and the result is ...
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Modelling a fully relativistic White Dwarf Star

I am trying to model a fully relativistic white dwarf using different central densities. Using the below equations: $\frac{dP}{dm} = -\frac{Gm}{4\pi r^4}$ $\frac{dr}{dm} = -\frac{1}{4\pi\rho r^2}$ and ...
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Why is the least massive neutron star less massive than the most massive white dwarf?

Martinez et al. (2015) gives an example of a neutron star with mass as low as $1.17M_\odot$ (solar masses). There is also the recent discovery of this candidate neutron star which is apparently only $...
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Numerical Integration for White Dwarf Model [closed]

I'm creating a numerical integration model of a white dwarf. So I've started with calculating electron pressure vs number density across a wide range of values. Using the equations of state in ...
Celina Emma's user avatar
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Proportion of Oxygen in a typical white dwarf

What's the proportion of Oxygen in a typical white dwarf relative to the proportion of Carbon?
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Are electrons bounded or unbounded to nuclei when they are degenerate?

I have a question about degenerate electrons in white dwarfs. So, as far as I know, when the gas contained in stars is compressed so much, the electrons start to fill the lowest energy level and then, ...
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How small would iron stars with a mass of 0.50 solar mass be?

I am wondering how small a 0.50 solar mass iron star would be. Would they be the same size as a white dwarf of that mass which would be about the size of the Earth. Or would they be much smaller and ...
Roghan Arun's user avatar
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If you were to (somehow) compress a golf ball so it fits into the radius of a grain of sand, how much energy would be released when it "sprung" back? [closed]

I'm curious approximately how much energy would be stored in the repulsion (both classical electrostatic, and any Pauli-type quantum effects) between the electrons if the "space" between the ...
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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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Could electrons tunnel into protons in a white dwarf and turn it into neutron star?

Just like the Sun, where hydrogen ions tunnel into each other to start fusion, which would be otherwise impossible with this level of kinetic energy, could electrons inside a white dwarf tunnel into ...
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Are all the electrons in a white dwarf degenerate?

White dwarfs are supported primarily, if not entirely, by degeneracy pressure from electrons. But are all the electrons degenerate, or are there still some electrons hanging around individual nuclei ...
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Why heating a white dwarf shrinks its degenerate core?

I tended to think that under electron degeneracy, electrons are spread over more energy states instead of being spread over so much space, so the exclusion principle lets more electrons to be ...
Jirka Hanika's user avatar
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Why is there no stars made of bosons?

Consider the white dwarf (or similarly neutron stars), which can be modeled as a star made of degenerate Fermi gas: A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed ...
Histoscienology's user avatar
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What happens when a helium white dwarf accretes enough matter?

What happens when a helium white dwarf accretes enough matter? Say you have a white dwarf made of helium, what happens when it's core becomes dense enough to fuse helium and how massive would it have ...
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Why are there no known white dwarfs between 1.35 to 1.44 solar masses?

The Chandrasekhar limit for white dwarfs is 1.44 Solar masses, however the heaveist known white dwarf is only 1.35 solar masses. https://earthsky.org/space/smallest-most-massive-white-dwarf/ What's ...
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What is the strength of Coulomb crystals?

Coulomb crystals are solid crystals made of ions embedded in an electron gas. They constitute much of white dwarfs and the crust of neutron stars. In the case of neutron stars it is known that they ...
Anders Sandberg's user avatar
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Neutron star forms after merging of white dwarfs?

In the news report 'A White Dwarf Living On The Edge' (Keck Observatory), Ilaria Caiazzo writes about a $1.35 M_\odot$ white dwarf which was formed by the merging of two less massive white dwarfs: “...
gamma1954's user avatar
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Is the center of the supergiant star a white dwarf?

According to An Introduction to Modern Astrophysics, there is a sentence in the book that describes a white dwarf at the center of a supergiant star. As far as I know, in the case of a heavy star, the ...
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Relation between central and mean density in a White Dwarf (polytropic model)

I'm currently studying the radius of a white dwarf and, in deriving some useful equations, I've seen my professor use the following relation: $\bar\rho=\frac{\rho_c}{6}$ when using a polytropic model $...
Jorge Casajus's user avatar
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Is a small fragment of a white dwarf stable? [duplicate]

Assuming it is somehow possible to get a small piece of a white dwarf (maybe a dice) and this piece escapes into free space. Would that piece of white dwarf matter keep its density/state, or would it ...
Charles Tucker 3's user avatar
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Does a star's emitted energy equal the work of its gravitational field?

Based on the formula of this question, it is possible to estimate the difference of the Sun's gravitational potential energy now and after it becomes a white dwarf. $$\Delta E = GM^2\left (\frac{1}{r_{...
Claudio Saspinski's user avatar
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1 answer
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Is there a point where the electrons can move no faster in degeneracy?

So my understanding of electron degeneracy is that as the area an electron is decreased, its oscillations increase in speed. Is there a point that it is moving at just under light speed and cannot ...
Rick's user avatar
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Equations of state for white dwarf stars

I am dealing with some model describing the given composition of a white dwarf made with photons, degenerate electrons, positrons and ions. From that, I can get tabulated values of densities ranging ...
Camillus's user avatar
2 votes
1 answer
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Jupiter-sized planet orbiting a white dwarf?

I read this news about a Jupiter sized planet orbiting a white dwarf. It is still puzzling to the scientists that how it remained as a single piece. NOTE: I went through the Astro.SE link given in ...
Ankit's user avatar
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Understanding the Chandrasekhar limit for white dwarfs and its relation with supernovas

So if I understand correctly, the Chandrasekhar limit ($\sim 1.4 \ M_{\odot}$) is the maximum mass that a white dwarf can have. Beyond this mass, the degeneracy pressure of the electrons can no longer ...
Guillermo Franco Abellán's user avatar
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Electron degeneracy in white dwarfs

Consider a plasma in a star. Now in a plasma electrons are so excited that they can no longer be held by the electromagnetic field of the nucleus. But then when we are talking about cores or red ...
user43470's user avatar
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White dwarf mass-radius relation

I have been reading about white dwarfs, whose radius-mass relation is: $R \sim M^{-1/3}$ because of the degeneracy pressure. Could anyone provide me with a qualitative explanation of this relation? I ...
alexsanchezcast's user avatar
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What is the effective radius of stellar graviton emission?

White dwarfs have been used to accurately determine photon gravitational redshift:https://scholar.google.co.uk/scholar?as_ylo=2016&q=white+dwarf+gravitational+redshift&hl=en&as_sdt=0,5#d=...
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Free decompression of white dwarf or neutron star matter -- what do we end up with?

(Possibly related: What would happen to a teaspoon of neutron star material if released on Earth?) Suppose that we somehow produced or obtained a small amount of neutron star matter or white dwarf ...
ikrase's user avatar
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Existence and evolution of P-type "asymmetrical binaries"

I'm not sure how those are called so let me explain what I mean by "P-type asymmetrical binaries" - I'm thinking of two stars of very different masses (originally) that orbit each-other fairly closely....
Rosh's user avatar
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4 votes
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White dwarf stars: limits to stability

The Chandrasekhar mass limit $M_\text{Ch}$ for a cold, non-rotating white dwarf star is derived from the hydrostatic equilibrium assuming Newtonian gravity and a Lane-Emden polytrope with n=3. However,...
gamma1954's user avatar
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5 votes
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What fuel is J005311 burning?

J005311 is two white dwarf stars that have merged in such a way, that, well they merged instead of exploding. (Only 7 or so such mergers have been found.) Its stellar wind is blowing at 16,000 km ...
Rick's user avatar
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3 votes
1 answer
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Does electron degeneracy pressure decrease over time in a star?

As far as i understand, electron degeneracy pressure relies upon the confined electrons having a lot of kinetic energy, which causes them to push 'outwards', counteracting gravitational pressure in a ...
Yuri's user avatar
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1 answer
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Pauli Exclusion and Black Holes [duplicate]

Pauli exclusion principle states that 2 identical electrons cannot be in the same state, where state includes a spacial component. I have heard that, in order to avoid being in the same state, in a ...
Nayeem Hossain's user avatar
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1 answer
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Why are more massive white dwarfs smaller?

I understand that a white dwarf is supported by the Pauli Exclusion Principle and that the larger the gravitational force against them, the closer the electrons must pack. But I have two queries: ...
Vishal Jain's user avatar
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1 vote
1 answer
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Wind-fed Accretion and White Dwarf stars

Can a White Dwarf star in a binary system accrete matter via the Wind-fed accretion process?
LightningStrike's user avatar
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1 answer
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Behaviour of a star as it approaches Ultrarelativistc limit

By considering the potential energy of a degenerate star of mass $M$ and radius $R$, I can use dimensional arguments to show that the radius of the star depends on its mass as: $$ R ∝ M^\frac{2-n}{...
DJA's user avatar
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Luminosity of a white dwarf

Why in an H-R diagram the white dwarfs are at the bottom left? I understand that they would have a high temperature when they are formed, and so at that instant shouldn't they have a high luminosity ...
Megan mars's user avatar
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1 answer
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Where are the high mass White Dwarfs that are going to create type 1a SN

The mass distribution of WD stars is explained at Why is the white-dwarf mass distribution highly peaked?. However this mass distribution shows very few stars that are about to exceed the WD limit of ...
JohnM's user avatar
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2 votes
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What fundamental force is at play in electron degeneracy pressure? [duplicate]

For example 2 electrons repel each other because they experience electromagnetic force, matter particles attract each other because they exert gravitational force on each other, fusion is possible ...
user6760's user avatar
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1 answer
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Could a sufficiently massive Dyson Sphere under very specific conditions depend solely on electron degeneracy pressure for structural integrity?

Stuck in an argument. I claim this is theoretically possible: Provided you could build a type 1 Dyson Sphere, made from a supposed material that rivals the structural integrity of a white dwarf, i.e. ...
GHolven's user avatar
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Would a Dyson sphere face physical limits faced by white dwarves?

During a recent online discussion, one of the participants made the claim that a Dyson sphere would be limited in mass by the Chandrasekhar limit. Attempts to solicit evidence for this claim were ...
readyready15728's user avatar
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1 answer
537 views

How to get the Chandrasekhar Limit from a plot?

at the moment I am trying to understand, how to obtain the Chandrasekhar mass limit from a plot like shown above. Because for $n$ = 3, the mass is independent of the radius of the white dwarf. But in ...
Armani42's user avatar
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8 votes
2 answers
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What is the theoretical lower mass limit for a white dwarf?

This question in inspired by this other one, which asks what is the theoretical lower mass limit for a gravitationally stable neutron star (not the Chandrasekhar limit which is the upper mass limit ...
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What is the Chandrasekhar-Friedman-Schutz (CFS) instability, exactly?

I am confused as to what the Chandrasekhar-Friedman-Schutz (CFS) instability is, exactly. It seems to refer to this paper by Chandrasekhar, but I do not think this paper covers the full instability. ...
user1379857's user avatar
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