Questions tagged [white-dwarf]

Questions about electron degenerate stellar remnants.

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Why does a white dwarf sometimes go 'nova' and sometimes supernova (type 1a)?

Obviously, when a white dwarf goes truly supernova, there is nothing left, not even, I have heard, a neutron star or black hole... But when certain white dwarf stars accrete certain amounts or types ...
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Where will all atoms on the Earth end up when the Sun engulfs the earth?

I am curious about what will happen to all atoms on the Earth including all of our atoms after the Sun engulfs the Earth? Will they become the part of the Sun's white dwarf? Or most of them will be ...
tvd's user avatar
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What are the most up to date, accepted, evolution stages of big stars that end in compact objects or a planetary nebula?

There are numerous charts and diagrams showing the stages of stellar evolution, as: or among many more (you can find several after googling a little), for example. When I studied my B.Sc. on Physics,...
omivela17's user avatar
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How to calculate the number density of electrons?

I am trying to calculate the number density of electrons (number of electrons/m^3) for a white dwarf, knowing these parameters : the mass and radius of the white dwarf (therefore its density (kg/m^3))...
Jean Pégoud's user avatar
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Question about a White Dwarf formula

I have a question regarding the White Dwarf radius formula given on wikipedia, in terms of what units I am supposed to use and what expected values of one variable would be. https://en.wikipedia.org/...
DanceroftheStars's user avatar
9 votes
1 answer
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Why would rocky earth-like planets be rare around white dwarf stars?

I came upon an article here https://phys.org/news/2023-11-white-dwarfs-life-planets.html The author thinks that rocky earth-like planets could be rare around white dwarfs.What could be the reason for ...
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What would the collapse of a white dwarf to a neutron star look it

It’s hypothesised that some white dwarves, when raised in mass above the Chandrasekhar limit, will instead of producing a type 1A supernova, will instead collapse into a Neutron star. What would this ...
blademan9999's user avatar
14 votes
3 answers
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Why do white dwarfs cool down so slowly?

I read that when white dwarfs do not proceed with nuclear fusion, the heat radiation from it is solely based on heat it retained in the past But then, it floats in an almost 0 K empty space. So, why ...
Zoli's user avatar
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Degenerate object accretion - what happens after it becomes a PMO?

Degenerate objects such as neutron stars and white dwarfs can be accreted from by other objects. As the degenerate object loses mass, it could pass through different mass ranges which govern the ...
WarpPrime'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?
blademan9999's user avatar
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What crystal structures are predicted for the crystalline phase of matter inside crystalizing white dwarfs? Does it depend on the carbon/oxygen ratio?

The abstract of Venner et al. (2023) A Crystallizing White Dwarf in a Sirius-Like Quadruple System includes the following: The location of HD 190412 C on the 𝑇eff − mass diagram implies it is ...
uhoh's user avatar
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How small stars help with planet formation

As I understood, low mass stars in their core go through fusion, but only the fusion of hydrogen happens. When it depletes hydrogen, fusion stops as temperature is still not high enough to support ...
Giorgi Lagidze's user avatar
18 votes
2 answers
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Why did Chandrasekhar use 2.5 for molecular weight in 1931?

I understand that the history of the Chandrasekhar limit is complicated (see, for example, Edmund C. Stoner and the Discovery of the Maximum Mass of White Dwarfs, Michael Nauenberg, JHA 39:297, 2008 / ...
Leos Ondra's user avatar
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What is the maximum radius of a pure iron-56 planet?

Suppose we are building a pure iron-56 planet atom by atom, how large can it get in terms of radius before it collapses into a black hole?
EFanZh's user avatar
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How does the Chandrasekhar limit relate to the ignition of carbon in white dwarf stars?

Why carbon in white dwarfs ignites (deflagrate, detonate) at the Chandrasekhar limit? The limit relates stability of the star made of degenerate electron Fermi gas to the white dwarf mass without a ...
Leos Ondra's user avatar
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3 votes
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After a Type Ia supernova explosion, what becomes of the degenerate matter?

A white dwarf below 1.44 solar mass in a binary system may accrete mass from its companion. If its core reaches the temperature for carbon fusion during this process, the white dwarf may reignite in a ...
Mys_721tx's user avatar
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How do I estimate the number of neutron stars and black holes relative to the number of stars in the main sequence and white dwarfs?

Recently, I had a homework question that gave me the mass of a main-sequence star, that is, M_tp = 0.9 M_solar, and the population formed at the same time. I am supposed to use the stellar birth ...
Casper's user avatar
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Do “neutrino supernovae” exist?

Core collapse supernovae release most of their energy in the form of neutrinos. About 1% of the neutrinos are absorbed by the thick outer envelope which powers a spectacular supernova explosion. Core ...
哲煜黄's user avatar
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1 answer
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What is the spectral reflection curve of cold white dwarfs and neutron stars?

Suppose that I got a white dwarf and a neutron star and after some trillions of years their temperature are down to just a few °K so cold that they don't emit any appreciable black body radiation. Now,...
Victor Stafusa - BozoNaCadeia's user avatar
8 votes
1 answer
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Are white dwarfs made of carbon or electron degenerate matter?

I know that white dwarfs are composed primarily of carbon but are supported by electron degeneracy pressure. Is the electron degeneracy pressure produced by carbon atoms, or is the core of the white ...
theta's user avatar
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What determines the temperature of a white dwarf?

Can someone please explain what determines the temperature of the white dwarf? Is more massive white dwarf hotter ? Also, is the density of a white dwarf always a constant?
Rian's user avatar
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The two channels of Type Ia SNe and their use as standard candles

As we know, Type Ia supernovae are used as standard candles since their absolute luminosities are expected to be roughly constant. The consensus model, as seen from the Wikipedia page, suggests this ...
YiFan's user avatar
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2 votes
2 answers
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What would be the product between the collision of a white dwarf and a main sequence star?

Would this ever happen? If it would, what kind of star/supernova would this create? Does it depend on the mass of the main sequence star?
Jack the Ranger's user avatar
5 votes
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Type Ia supernova by fallback?

Is it possible for a massive star of more than 1.4 solar masses (probably around 3 or more but below the threshold for type II) to collapse into a white dwarf and a planetary nebula, then go supernova ...
WarpPrime's user avatar
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12 votes
2 answers
204 views

Hypothetical upper and lower bounds for Chandrasekhar limit based on composition?

Disclaimer: I'm going to be using the term "white dwarf" to refer to any spherical celestial body made of electron degenerate matter. If I had a better term, I would use it. The ...
zucculent's user avatar
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Do gamma rays escape from stars when turning into white dwarfs

I'm very curious about this : if the Sun were to become a white dwarf, would Earth get blasted with high-energy electromagnetic radiation? I know that current predictions say that Earth will be ...
Dave's user avatar
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8 votes
1 answer
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Do all C-O white dwarfs have more-or-less the same proportions of carbon and oxygen?

Type 1a supernovae are known for having very consistent energy yields, and they are caused when a carbon-oxygen white dwarf reaches the Chandrasekhar limit of about 1.4 solar masses. Since type 1a ...
zucculent's user avatar
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1 vote
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156 views

What does an electron-capture supernova leave behind? A white dwarf, a neutron star or nothing?

Somehow, none of the many articles I've read about the recent discovery of electron-capture supernovae has specifically said what they leave behind as remnants.....
Kurt Hikes's user avatar
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Is something wrong with my luminosity calculation?

A few million years after a white dwarf forms, its surface temperature reaches $100000\text{K}$, while its radius is $0.01R_\odot$. Would this mean that its luminosity is $\Big(\dfrac{100000}{5778}\...
WarpPrime's user avatar
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3 votes
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Uranium accumulating inside a White Dwarf?

A couple of days ago, there was news that "Some dead stars may harbor enough uranium to set off a thermonuclear bomb", which is basically a teaser for Actinide crystallization and fission ...
B--rian's user avatar
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3 votes
0 answers
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Can mass loss via accretion occur on stellar remnants?

We know that normal stars can lose mass to a binary companion. But can this happen to neutron stars and white dwarfs? Let's say a stellar black hole is being orbited by a white dwarf or neutron star. ...
slowerthanstopped's user avatar
2 votes
0 answers
101 views

What would happen if a neutron star merged with a white dwarf?

We've heard of neutron star mergers and white dwarf mergers. But what would result in a neutron star merging with a white dwarf? Would there be a similar super/kilonova, are there any examples of it, ...
slowerthanstopped's user avatar
2 votes
1 answer
247 views

Would dropping a white dwarf or a "still-hot" stellar core into a large planet or brown dwarf create a star?

In the Wikipedia article about stellar engineering, I found this quote: In The Saga of the Seven Suns, by Kevin J. Anderson, humans are able to convert gas giant planets into stars through the use of ...
WarpPrime's user avatar
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7 votes
1 answer
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Exactly how long does it take for the exposed core of a star to cool from its starting temperature (several billion K) to ~50,000 K?

OK, I didn't know how I should word this question. But the basic point is that most white dwarfs that we have classified fall in temperature ranges from ~50,000 K to 6000 K. However, at the end of a ...
WarpPrime's user avatar
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3 votes
1 answer
287 views

What is the coolest white dwarf known?

Okay, so in this ArXiv report from 2014, scientists discovered the coolest white dwarf, with a temperature of below 3000 K. However, as this report was from over 6 years ago, I think this information ...
WarpPrime's user avatar
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3 votes
0 answers
62 views

How long does it take for a white dwarf to undergo a type Ia supernova?

I read about white dwarfs and their relation to Type Ia supernovae, and I want to know how much time passes between when the white dwarf passes the Chandrasekhar limit and when the white dwarf ...
WarpPrime's user avatar
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3 votes
1 answer
572 views

Do more massive stars become larger or smaller white dwarfs?

I wonder whether e.g. stars more massive than the Sun (but below the mass where they'd go supernova) would become larger or smaller white dwarfs than a white dwarf Sun. Since Procyon B is larger than ...
Greenhorn's user avatar
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1 answer
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Assuming proton decay is false, what's the ultimate fate of a neutron star or white dwarf?

A still unproven theory that protons can decay, and have a halflife of $10^{30}$ years or so, meaning eventually all matter will dissolve because their constituent protons and therefore neutrons will ...
user random numbers's user avatar
-2 votes
2 answers
314 views

How can planet (WD 1856b) revolve around its smaller mass WD 1856?

WD 1856 has smaller mass than WD 1856b. So how WD1856 making WD 1856b revolve in the orbit? Its clear violating space-time curvature.
Kate Marie's user avatar
6 votes
1 answer
435 views

What's the big deal with WD 1856+534 b?

A few days ago (september 2020) a planet candidate was announced orbiting white dwarf WD 1856+534. Some media outlets announce it as the First Possible ‘Survivor’ Planet around a white dwarf, while ...
Rafael's user avatar
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11 votes
1 answer
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If Sunlike stars become a red giant and eventually a white dwarf, what do red dwarfs become?

The Sun is said to become a red giant at the end of its life (before that it will become an orange subgiant first and then an orange giant or so) and after ejecting its outer layers it should become a ...
Giovanni's user avatar
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2 votes
1 answer
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Is the object a pulsar

We have a star having 1.8 solar mass. Justify any four means (measurable/ observed properties) by which you can identify that the object is a Pulsar and not a white dwarf or a Black Hole. So one ...
sanchit krishna's user avatar
6 votes
1 answer
255 views

What is considered "contact" for contact binary white dwarfs, and roughly how long can they stay that way before merging?

The question Why do they think that WDJ0551+4135 is “snowman shaped” i.e. a contact binary? has also raised the question of what a contact binary is or isn't, and how hard it might be to see one if it ...
uhoh's user avatar
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4 votes
1 answer
243 views

Can white dwarfs have accretion discs too?

Neutron stars and black holes can have discs of accreted matter for they have an extremely high gravitational pull. While white dwarfs don't have such high gravity theirs is of course also extremely ...
user30007's user avatar
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10 votes
1 answer
795 views

The colour of blue dwarf stars

The paper "M dwarfs: planet formation and long term evolution" describes blue dwarf stars, a hypothetical next-stage in the lifespan of red dwarf stars within a certain mass range, after which they ...
Astrid_Redfern's user avatar
2 votes
0 answers
59 views

Could an Applegate-like mechanism operate in AM CVn systems?

One of the controversies surrounding the detection of exoplanets around post-common envelope binaries is the possibility that the orbital period variations observed might be the result of the ...
user avatar
1 vote
1 answer
130 views

Higgs Field inside a White Dwarf

White dwarfs rank among the hottest things in the universe. In the early years of the life of the universe, universe was very hot and the Higgs field was deactivated causing all the particles ...
Warrior's user avatar
  • 53
6 votes
2 answers
263 views

Why would tidal forces on planets become more intense when a star becomes a white dwarf?

I was puzzled by this press release by the Royal Astronomical Society: "Small, hardy planets most likely to survive death of their stars" - phys.org, May 14, 2019 Astrophysicists from the Warwick ...
Jacob C.'s user avatar
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3 votes
3 answers
643 views

Do white dwarfs produce stellar wind? If not, why is that?

I've been told white dwarfs don't produce stellar wind like the sun produces solar winds. I don't quite understand why that is and can't really find any evidence that confirms or denies that. My ...
White Dwarf's user avatar
1 vote
2 answers
272 views

Do white dwarfs lose mass as they fade to black dwarfs? Is there a correlation between temperature, mass, and radius?

I'm having a difficult time understanding certain behaviors of white dwarfs. I understand how mass is lost in the red giant to white dwarf transition process. I understand that white dwarfs can ...
White Dwarf's user avatar