Questions tagged [white-dwarf]
Questions about electron degenerate stellar remnants.
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If two white dwarfs collided, would they become a star?
Would the temperatures during such a collision be able to ignite nuclear fusion, bringing the dead star back to life? If so, would it only be able to fuse for a short time before running out of fuel, ...
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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 / ...
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How long does it take for a white dwarf to cool to a black dwarf?
I was reading on white dwarfs, and I came across this sentence—
Without energy sources, the white dwarf cools to a black dwarf in a few billion years.[1]
However, when I looked into the Wikipedia ...
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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 ...
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How much mass will the Sun have when it becomes a white dwarf?
In 4 billion years, when our Sun sheds all of its outer gas layers and turns into a white dwarf, how much mass will the white dwarf have compared to what the sun has today?
Will the planets still ...
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Is there a possibility that a white dwarf can turn into a neutron star or a black hole?
I know that a white dwarf is supported mainly by electron degeneracy pressure and that if it gains more than about 1.4 solar masses from any source (such as a companion star or a collision), it ...
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Will Sirius B start accreting from A and become a supernova type Ia?
Sirius B is a massive white dwarf of 1 Solar mass, orbiting at about 25 AU distance from the 2 Solar mass Sirius A. As it evolves and expands, will the A star start shedding matter to the white dwarf, ...
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How do stellar temperatures vary?
The temperature of the surface of the Sun (photosphere) is between 4500° - 6000° Kelvin. Inside the core, it's around 15.7 million degrees Kelvin.
In other types of stars (neutron stars, white ...
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How is the first detonation in Supernove type Ia triggered?
Ok, I read about the Supernova of type Ia and I found out that there are two detonations happening. First one is in helium shell around the white dwarf and second one seems to be triggered by the ...
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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 ...
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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 ...
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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 ...
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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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Are white dwarf stars supported by proton degeneracy as well?
In general, fermions form a degenerate gas under high density or extremely low temperature. It's clear that white dwarf stars are supported by electron degeneracy pressure. However, there are still a ...
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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 ...
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Why does the Chandrasekhar limit affect white dwarfs differently?
The Chandrasekhar limit is the maximum mass of a stable white dwarf star. Beyond this, a carbon-oxygen white dwarf will typically explode in a type 1a supernova, due to the nuclear reactions at those ...
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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 ...
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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 ...
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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 ...
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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 ...
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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,...
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Which Chandrasekhar Limit do I use? 1.39 or 1.44?
Different sources online say that the Chandrasekhar Limit is either 1.40 or 1.39, or 1.44 solar masses. Why the discrepancy? I heard it might have to do with the composition of the white dwarf, but, ...
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White Dwarf and Degenerate Matter
How do we know degenerate matter exists on white dwarfs? Is it purely hypothetical or have we observed it before? Have we ever created a form of degenerate matter on earth?
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If a white dwarf collides with a giant star, could it create a TZO?
Thorne–Żytkow objects (TZOs) form from collisions between neutron stars and main sequence or giant stars. Ultimately, the neutron star becomes the "core" of the giant star.
However, could this also ...
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Chemical reactions in white dwarf and carbon allotropes
White dwarfs consists mostly of carbon and oxygen. In my opinion, they are too hot to contain these elements in molecular form and hence chemical reactions does not happen (I think resulting CO2 will ...
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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 ...
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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 ...
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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 ...
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What does a black dwarf look like?
A black dwarf is a hypothetical object that is the end result of the cooling of a white dwarf. None yet exist, because there hasn't been enough time in the age of the universe for them to cool down ...
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How can white dwarf form Oxygen ? (Temperature problem)
I’ve got a question about white dwarfs and oxygen.
I read in a book that a temperature of 100 million degrees is required to fuse Helium in the core of a red giant. The Helium fuses into Carbon by ...
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White dwarf's impact on orbiting bodies
Recently the Kepler telescope in its study of white dwarfs detected the first planetary object transiting a white dwarf in the data from the K2 mission. It was consistent with earlier theories' ...
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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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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 ...
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White dwarf supernova luminosity
I understand that the mass limit for a white dwarf is 1.4 solar masses, and therefore approaching it would cause a white dwarf (type Ia) supernova, and thus it is a standard candle. I understand this ...
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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 ...
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Required temperature for a nova
On the wikipedia page of the nova is said that the CNO cyle, which converts hydrogen into helium, starts on the surface of the white dwarf when the temperature reaches about 20 million K.
My question ...
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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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How does a planet lose mass to its host star?
How do bodies like WASP-12b lose mass to its central body? The process is never really explained in popular media, instead showing visualisations of a thin veil of gas being "sucked" in a rather ...
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What is "superficial gravity"
I have seen the term superficial gravity used and it seems to be equivalent to surface gravity
seen, e.g., here http://arxiv.org/pdf/1701.02295
Is there any difference between superficial and ...
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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,...
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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 ...
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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 ...
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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?
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Do neutrinos account for approximately 99% of the energy released by Type 1a supernovae as they do for Type II 'Core collapse' supernovae?
So many accounts say that neutrinos carry away about 99 percent of the energy from a 'traditional' supernova (giant star at end of its life), but what about a white dwarf detonated after accretion?
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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))...
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Can life survive on the equator of cooled and fast rotating white dwarf or neutron star?
As I know, some stars produces carbon, nitrogen and oxygen when they are old and become white dwarfs or neutron stars. And even their surface gravity is strong, it may rotate very fast so that the ...
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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 ...
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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 ...
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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 ...
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Have any more "white dwarf pulsars" been discovered or searched for?
Back in 2016, Marsh et al. reported that the binary system AR Scorpii exhibits complex radio signals similar to those observed from traditional pulsars. In particular, pulsed synchrotron emission ...
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