Questions tagged [white-dwarf]

Questions about electron degenerate stellar remnants.

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32
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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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3answers
4k views

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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2answers
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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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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, ...
13
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2answers
3k views

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 ...
12
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1answer
208 views

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 ...
10
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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 ...
10
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5answers
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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 ...
8
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2answers
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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 ...
8
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1answer
502 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 ...
7
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1answer
75 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 ...
7
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2answers
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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 ...
6
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1answer
858 views

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?
6
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1answer
285 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 ...
6
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1answer
146 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 ...
6
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2answers
879 views

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 ...
6
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3answers
604 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 ...
6
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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 ...
6
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2answers
349 views

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' ...
6
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2answers
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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 ...
5
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2answers
483 views

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, ...
5
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1answer
323 views

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 ...
5
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1answer
141 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 ...
5
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1answer
126 views

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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0answers
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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 ...
4
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3answers
336 views

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 ...
4
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1answer
89 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 ...
4
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1answer
165 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 ...
4
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2answers
278 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?...
4
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1answer
449 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 ...
3
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3answers
347 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 ...
3
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2answers
779 views

Cosmic events as standard candles

Type 1a supernovae are used as standard candles. Are there other high energy cosmic events which can be used as standard candles. For example, collapse of neutron star into a black hole is also ...
3
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1answer
101 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 ...
3
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1answer
329 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 ...
3
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1answer
146 views

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 ...
3
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1answer
193 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
87 views

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 ...
3
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1answer
978 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, ...
3
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0answers
97 views

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 ...
3
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0answers
46 views

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. ...
3
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0answers
45 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 ...
2
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2answers
924 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?
2
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2answers
493 views

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 ...
2
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2answers
245 views

What is the most distant observable White Dwarf known?

I attended a talk last week about Type 1a supernovae with the focus being on double-degenerate systems as potential progenitors for them. We were shown a graph of White Dwarf (WD) mass distribution ...
2
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1answer
125 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 ...
2
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1answer
115 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 ...
2
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1answer
124 views

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 ...
2
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1answer
236 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 ...
2
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1answer
94 views

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 ...
2
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0answers
62 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, ...