Questions tagged [white-dwarf]

Questions about electron degenerate stellar remnants.

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7
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1answer
61 views

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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1answer
81 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 ...
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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 ...
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3answers
549 views

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 ...
3
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1answer
90 views

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 ...
3
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1answer
284 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 ...
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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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4answers
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What is the difference between a neutron star and a white dwarf?

What is the difference between a neutron star and a white dwarf? I know that both are very dense even if they go through different phases.
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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.
4
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1answer
389 views

How bright can white dwarf stars glow as they accrete matter?

I realize this is kind of general as it would depend on the size of the white dwarf and the rate of accretion. The general idea I got thinking about is what would happen if a white dwarf star - lets ...
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39 views

How bright would a magically created 13.7B years ago white dwarf be now?

I assumed that the initial brightness is $1$, and at death it is $10^{-20}$ (since I can't reach 0 with exponentiation, it will be close enough to 0), and it lived $10^{15}$ years. Then I solved an ...
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Are the terms “PG 1159 star” and “pre-white dwarf” synonymous?

Are the terms "pre-white dwarf" (as in Gies et al. 2020, "Spectroscopic Detection of the Pre-White Dwarf Companion of Regulus") and "PG 1159 star" (as described, e.g. in ...
6
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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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1answer
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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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1answer
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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 ...
6
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1answer
132 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 ...
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1answer
75 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 ...
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1answer
382 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 ...
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2answers
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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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4answers
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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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0answers
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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 ...
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1answer
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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 generated ...
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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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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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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 ...
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Can life on earth be supported by only a Red Dwarf star or a White Dwarf(state still hot not cooled enough yet)?(Provided it is near to the star)

Can a red dwarf star or a white dwarf have enough energy to support life on earth? How it will change the climate and the seasons of earth if it is our only star? (energy source)(Expecting it to ...
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2answers
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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 ...
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1answer
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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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Are white dwarfs the ones always absorbing mass from a companion?

It seems to me every time I see stellar remnant binary systems where there is a white dwarf and another star or something, it appears that the white dwarf always pulls mass from the star. What if the ...
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1answer
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White Dwarf/Degenerate Gas Behaviour

just want to try to clarify a few things about the nature of White Dwarfs and degenerate gases. So if a white dwarf is help up by an electron degenerate gas, the electrons are unable to lose energy ...
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1answer
5k views

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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1answer
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Is the structure of crystalized white dwarf related to nuclear pasta?

There is news of an analysis of a large number of nearby white dwarfs revealing a "pile-up" at a certain point in their cooling which has been predicted to happen due to a phase change where nuclear ...
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1answer
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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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3answers
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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 mainly balanced by electron degeneracy pressure and that if it gains more than 1.4 solar masses from any source (such as a companion star or a collision), it explodes as a ...
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2answers
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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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1answer
514 views

Question about number density of electrons

I somewhere see that in a white dwarf, we have this equation: $\rho = 2 N_e * m_p / V = 2 n_e * m_p$ where $N_e$ is the number of particles (in this case e, electrons) and $n_e$ is the number ...
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1answer
743 views

Gaia Gbp - Grp: why does it get larger as star gets redder?

As an enthusiastic amateur scientist, I'm plowing my way through a cool Gaia DR2-based paper, "An Empirical Measurement of the Initial-Final Mass Relation with Gaia White Dwarfs". I'm doing all right, ...
5
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1answer
140 views

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 ...
4
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1answer
147 views

Would the heliosphere disappears if our sun becomes a white dwarf?

Just curious I like to know if one fine day our Sun turns into a white dwarf at the later stage of its life, would the magnetic bubble, heliosphere gets thinner and eventually disappear? also at this ...
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2answers
800 views

What happens if a white dwarf collides with a star like our sun or a red dwarf?

Would it explode in a supernova or will it form a new star?
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1answer
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What if a white dwarf is less massive than her partner?

For example: a system with a 0.2 solar mass white dwarf orbiting a 0.25 solar mass red dwarf. Does the red dwarf steals mass from the white dwarf or vice versa.
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1answer
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What is the condition for the number density of a gas to be ultra-relativistic or non-relativistic and degenerate or ideal

What is the condition for the number density ($n$) of a gas to be ultra-relativistic or non-relativistic and degenerate or ideal? I found problems in this subject when I was reading about White-...
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1answer
191 views

What is a cold white dwarf?

Is a cold (3800K, or so) white dwarf still be considered/in degenerate state. Or, how can a gas be degenerate and cold?
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Which would be safer: removing hydrogen or adding hydrogen to our sun?

If we want to extend the lifespan of our habitable zone safely, would it be safer to institute a yearly 'tax' on our suns outer layer of hydrogen, or a yearly 'subsidy' to our suns outer layer of ...
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2answers
259 views

Origin of terms “white dwarfs” and “red giants”?

Can someone explain my why "white dwarfs" and "red giants" were so named? And maybe that's a silly question but why not in the opposite way? @EDIT Is this somehow co-related with Stefan–Boltzmann law?...
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1answer
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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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1answer
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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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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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1answer
232 views

Are there radio white dwarfs?

We have discovered about 2500 radio pulsars. Part of them show pulsations in other bands like X-ray and gamma ray. The radiation mechanism remains unclear now. I wonder whether there are radio ...
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1answer
112 views

white-dwarf merge in binaries

Two white dwarfs with a total mass $>1.4\:M_{\odot}$ merge. It may trigger a type Ia SN explosion. How about the three cases below? Two low mass WDs merge, total mass $<1.4\:M_{\odot}$. A low ...