Neutron Star Questions: Answers to Max/Min Mass & More

[Stephanus]

Dear PF Forum,
I have question concerning neutron star and star just simply out of curiousity.
1. Can a star reach silicon burning stage then stop. It doesn't continue to iron burning stage.
2. Once a star reach iron burning stage, there's no stopping it to blast into supernova? Is supernova inevitable for iron burning stage?
3. Does the density of neutron star equal to atomic nucleus?

These ones I should have googled it, but can't find a definite answer.
4. What is the maximum mass of a neutron star?
5. What is the minimum mass of a neutron star?

Thanks.

 

[John Rampton]

The accepted range for neutron star masses are between 1.4 and 3.0 Solar masses

 

[newjerseyrunner]

Is supernova inevitable for iron burning stage?

Once a star starts to burn iron, it's actually losing energy. Outward pressure from left over energy of nuclear fusion is what keeps the star from imploding. When you fuse hydrogen to hydrogen you get a lot of energy. Helium and helium make less energy. Once you get to iron, fusion doesn't actually provide any energy anymore, it starts drawing it away. So not only has the star run out of fuel to sustain it's outward pressure, but the remaining fuel is actually cooling the star and decreasing the pressure. This causes the collapse and explosion.

 

[Stephanus]

Once a star starts to burn iron, it's actually losing energy. Outward pressure from left over energy of nuclear fusion is what keeps the star from imploding. When you fuse hydrogen to hydrogen you get a lot of energy. Helium and helium make less energy. Once you get to iron, fusion doesn't actually provide any energy anymore, it starts drawing it away. So not only has the star run out of fuel to sustain it's outward pressure, but the remaining fuel is actually cooling the star and decreasing the pressure. This causes the collapse and explosion.

Hydrogen to Helium, you mean?
The pressure increase you mean?
So, once iron burning, the fate of the star is sealed to be supernova?

 

[SteamKing]

Dear PF Forum,
I have question concerning neutron star and star just simply out of curiousity.
1. Can a star reach silicon burning stage then stop. It doesn't continue to iron burning stage.
2. Once a star reach iron burning stage, there's no stopping it to blast into supernova? Is supernova inevitable for iron burning stage?
3. Does the density of neutron star equal to atomic nucleus?

These ones I should have googled it, but can't find a definite answer.
4. What is the maximum mass of a neutron star?
5. What is the minimum mass of a neutron star?

Thanks.

So, once iron burning, the fate of the star is sealed to be supernova?

Yes, and very quickly. Once the core starts burning silicon, these reactions play out within a matter of a few days.

For a star with an initial mass 25 times that of the sun, silicon burning might last 5 days:

https://en.wikipedia.org/wiki/Type_II_supernova

 

[newjerseyrunner]

Hydrogen to Helium, you mean?
The pressure increase you mean?
So, once iron burning, the fate of the star is sealed to be supernova?

I spoke with ambiguity, I meant hydrogen to hydrogen to mean H + H = He.

And no, the pressure decreases, the supernova isn't caused by increasing pressure in the core, it's caused by a rebound. Imagine holding a stone at the surface of water, now let it go. The rock pushes some water out of the way or splashes, but that's not important in my analogy, what's important is what happens next. You have an area where water used to be, where there is none now, so water from all directions rushes into fill the void. As the water does this, obviously too much water rushed in at once and it's momentum provides the energy to push a column of water straight up.

That's analogous to the supernova. The core cools while it burns iron, causing it to contract. The guts of the star rush into fill the void left by the shrinking core, bringing the weight of the star with it. All of this energy hits the core, which is compressed into pure neutron matter, which can not be compressed anymore, so the rest of the star coming down on it bounces, with extra energy created by conversion to neutron matter. That bounce rushes to the surface like in the water analogy and when it reaches the surface of the star it erupts.

It might interest you to know that there is a time delay of about three hours from when the core actually implodes and when the surface explodes. It's measurable because the collapsing core creates both energy and neutrinos. The energy propagates through the matter, the neutrinos fly straight through it at nearly the speed of light. Neutrino telescopes detect supernovas before telescopes can.

 

[Stephanus]

Yes, and very quickly. Once the core starts burning silicon, these reactions play out within a matter of a few days.

For a star with an initial mass 25 times that of the sun, silicon burning might last 5 days:

https://en.wikipedia.org/wiki/Type_II_supernova

Can silicon burning stop because of insufficient mass?

 

[Stephanus]

I spoke with ambiguity, I meant hydrogen to hydrogen to mean H + H = He.

Ok

And no, the pressure decreases, the supernova isn't caused by increasing pressure in the core, it's caused by a rebound.

That's analogous to the supernova. The core cools while it burns iron, causing it to contract. The guts of the star rush into fill the void left by the shrinking core, bringing the weight of the star with it. All of this energy hits the core, which is compressed into pure neutron matter, which can not be compressed anymore, so the rest of the star coming down on it bounces, with extra energy created by conversion to neutron matter.

Iron fusion absorbs energy, right?.
So
- Absorbing energy, cools the core.
- Cool contracts the core.
- Contracting core fuses iron quicker, and on, and on, and on, until BLAMM!
I think the pressure is increasing. It's the triumph of gravity force over nuclear force. If you call "iron burning" is nuclear force, because it absorb energy.
I just want to know, in some white dwarf, the fusion stops at Hydrogen burning, sometimes helium burning, sometimes for heavier star -> Carbon burning then stop.
I just want to know whether there is a sillicon white dwarf. Or if sillicon start to fuse, then it goes unstoppable to iron burning.
Or whether a star can contain only iron, the fusion stops at iron and doesn't produce supernova.

That bounce rushes to the surface like in the water analogy and when it reaches the surface of the star it erupts.

I like two marbles analogy. Hold two marbles up and down $_0^0$ drop them. When lower marble hits the ground it bounces up and hit the upper marble which goes down and bounce the upper marble higher. Clifford Johnson has a video in youtube showing this.

It might interest you to know that there is a time delay of about three hours from when the core actually implodes and when the surface explodes. It's measurable because the collapsing core creates both energy and neutrinos. The energy propagates through the matter, the neutrinos fly straight through it at nearly the speed of light. Neutrino telescopes detect supernovas before telescopes can.

Yeah about three hours. I once saw Michio Kaku (or Neil Degrasse Tyson) video, showing neutrino observatory 100 metres underground. - What sane people builds an observatorium 100 metres underground - it's said.

 

[SteamKing]

Can silicon burning stop because of insufficient mass?

No. If the nuclear reactions stop for any reason, gravity causes the core to shrink, raising its temperature until the reactions start again. This process will continue until there is no more silicon left to burn. Once that occurs, final core collapse is imminent.

Throughout their lives, stars operate by balancing the contraction of their mass due to gravity against the tendency of the hot gas to expand. Once the nuclear fusion at the core is not able to supply sufficient heat to keep gravity at bay, the core shrinks until either new fusion reactions can supply the necessary energy to prevent collapse, or the core collapses completely.

Smaller stars, like the sun, do not have enough initial mass to become supernovas. Instead, their cores fuse into carbon, after which the core becomes stable enough to keep from collapsing any further, because gravity is not strong enough to overcome the forces present in the carbon nucleus.

 

[Stephanus]

No. If the nuclear reactions stop for any reason, gravity causes the core to shrink, raising its temperature until the reactions start again. This process will continue until there is no more silicon left to burn. Once that occurs, final core collapse is imminent.

Throughout their lives, stars operate by balancing the contraction of their mass due to gravity against the tendency of the hot gas to expand. Once the nuclear fusion at the core is not able to supply sufficient heat to keep gravity at bay, the core shrinks until either new fusion reactions can supply the necessary energy to prevent collapse, or the core collapses completely.

Smaller stars, like the sun, do not have enough initial mass to become supernovas. Instead, their cores fuse into carbon, after which the core becomes stable enough to keep from collapsing any further, because gravity is not strong enough to overcome the forces present in the carbon nucleus.

So the boundary is carbon? What about nitrogen oxygen, if the star produces oxygen, it will not stop until supernova?

 

[SteamKing]

So the boundary is carbon? What about nitrogen oxygen, if the star produces oxygen, it will not stop until supernova?

There are a whole host of different nuclear reactions which occur at each stage.

Please read the Wiki article below about supernovas, along with any other articles to which it refers.

https://en.wikipedia.org/wiki/Supernova

Core collapse supernovas are Type II.

It's going to take more than a few minutes to read and digest all this material. It forms a good part of a course in stellar astrophysics.

 

[Stephanus]

There are a whole host of different nuclear reactions which occur at each stage.

Please read the Wiki article below about supernovas, along with any other articles to which it refers.

https://en.wikipedia.org/wiki/Supernova

Core collapse supernovas are Type II.

It's going to take more than a few minutes to read and digest all this material. It forms a good part of a course in stellar astrophysics.

Thanks for the link SteamKing, but it's not the supernova that I want to know, it's the element that stop the fusion. Perhaps for a cetain mass, carbon or oxygen? Then there's a carbon star or an oxygen star. What is the heaviest element for a stable star. Oxygen?

 

[SteamKing]

Thanks for the link SteamKing, but it's not the supernova that I want to know, it's the element that stop the fusion. Perhaps for a cetain mass, carbon or oxygen? Then there's a carbon star or an oxygen star. What is the heaviest element for a stable star. Oxygen?

AFAIK, white dwarf stars, like what our sun will eventually evolve into, are composed mostly of carbon. The star loses its envelope, and the carbon core eventually cools off, leaving a rather dense cinder, which is about the size of the earth, but with a mass about the same as the sun's.

If this white dwarf star has a younger star companion orbiting close by, the stellar remnant can accrete hydrogen and lighter elements on its surface, which build up until fusion occurs. This will, at the least, create what is known as a nova (rather than a supernova), which becomes temporarily brighter than original. If enough material collects suddenly, the new fusion reactions will be strong enough to destroy the star completely. This is a Type I supernova.

If a star is massive enough initially to fuse its core into oxygen and heavier elements, the evolutionary processes in the star will not stop until core collapse eventually occurs, resulting in a Type II supernova.

 

[Stephanus]

AFAIK, white dwarf stars, like what our sun will eventually evolve into, are composed mostly of carbon. The star loses its envelope, and the carbon core eventually cools off, leaving a rather dense cinder, which is about the size of the earth, but with a mass about the same as the sun's.

Size like earth, mass like sun, carbon high pressured. I once read, is that really a diamond?

If this white dwarf star has a younger star companion orbiting close by, the stellar remnant can accrete hydrogen and lighter elements on its surface, which build up until fusion occurs. This will, at the least, create what is known as a nova (rather than a supernova), which becomes temporarily brighter than original. If enough material collects suddenly, the new fusion reactions will be strong enough to destroy the star completely. This is a Type I supernova.

Yep, Type I supernova., Standard candle?

If a star is massive enough initially to fuse its core into oxygen and heavier elements, the evolutionary processes in the star will not stop until core collapse eventually occurs, resulting in a Type II supernova.

Now, THAT'S what I want to know. So it is oxygen.
Thanks.
I didn't know what should I put my title in this question that Greg Bernhardt gave me a general warning: Wrong Title!
With all these questionings, all I want to know is just: Oxygen.

 

[SteamKing]

Size like earth, mass like sun, carbon high pressured. I once read, is that really a diamond?

No one knows for sure. As in all stars, there is a mixture of elements in the core. A white dwarf may be predominantly carbon, but other elements, like oxygen, are present. Due to the high temperature in the core and the high gravity, the core material exists in a degenerate state, not the crystalline structure which makes up a diamond.

White dwarf stars can stay very hot for long periods of time. While the core temperature may be 10 million K, the surface temperature is generally 10,000 K and below to about 4000 K. The reason that white dwarfs are not found with cooler surface temperatures is that the universe is not old enough for these stars to have cooled below this temperature.

https://en.wikipedia.org/wiki/White_dwarf

Yep, Type I supernova., Standard candle?

I believe there is some controversy about this, due to recent findings.

http://www.astronomy.com/news/2014/03/standard-candle-supernovae-are-still-standard-but-why

Today, Pluto is a planet. Tomorrow, it's a dwarf planet. Things scientific are subject to change.

Now, THAT'S what I want to know. So it is oxygen.
Thanks.
I didn't know what should I put my title in this question that Greg Bernhardt gave me a general warning: Wrong Title!
With all these questionings, all I want to know is just: Oxygen.

As I mentioned above, stellar interiors are a mixture of every element which has been made in the star, starting with hydrogen and running down the list to oxygen or whatever.

Carbon burning sometimes leads to oxygen, sometimes to other elements like neon or magnesium. It's a complicated process. Sometimes, in the same star, different fusion paths are taken at the same time, leading to different end products.

Stars with different initial masses take different evolutionary paths. That's why I suggest you study more and make hasty generalizations less.

https://en.wikipedia.org/wiki/Carbon-burning_process

 

[Stephanus]

Today, Pluto is a planet. Tomorrow, it's a dwarf planet. Things scientific are subject to change.

Yeah, thanks to Neil Degrasse Tyson.

Stars with different initial masses take different evolutionary paths. That's why I suggest you study more and make hasty generalizations less.

https://en.wikipedia.org/wiki/Carbon-burning_process

Thanks for the link.

 

[Ken G]

I actually don't think the iron ever fuses in the star, not until the supernova itself. It is true that the supernova is caused by heat loss from the core, but it's not due to iron fusion, it's the opposite of that-- the temperature gets so high that iron is "photodisintegrated", which more or less undoes the heat-releasing fusion processes that led to the iron in the first place. Neutrino escape is a also a key heat-loss mechanism. But the basic idea is right-- when a core starts a runaway process of heat loss, it is doomed to collapse and supernova. A minor point: all supernovae are core collapse except type Ia (and others of the same ilk). It's not as simple as saying that type II are core collapse, type II just means there is still hydrogen in the stellar envelope when it core collapses.

 

[SteamKing]

I actually don't think the iron ever fuses in the star, not until the supernova itself. It is true that the supernova is caused by heat loss from the core, but it's not due to iron fusion, it's the opposite of that-- the temperature gets so high that iron is "photodisintegrated", which more or less undoes the heat-releasing fusion processes that led to the iron in the first place. Neutrino escape is a also a key heat-loss mechanism. But the basic idea is right-- when a core starts a runaway process of heat loss, it is doomed to collapse and supernova. A minor point: all supernovae are core collapse except type Ia (and others of the same ilk). It's not as simple as saying that type II are core collapse, type II just means there is still hydrogen in the stellar envelope when it core collapses.

When silicon burning takes place in the stellar core, nickel-56 (HL = 6 days) is produced. This is a radioactive isotope which decays first into cobalt-56 (HL = 77 days) and then iron-56.

When the collapse actually occurs, the iron-56 nuclei undergo photodisintegration into free neutrons and helium-4 nuclei as the rapidly heating core creates much gamma radiation. As the density of the core continues to increase, then any free protons and electrons remaining combine by reverse beta process to create even more neutrons and neutrinos. The neutrinos escape the core, carrying energy away, which accelerates the collapse even faster.

https://en.wikipedia.org/wiki/Type_II_supernova#Formation

 

[Chronos]

Iron cannot fuse it requires more energy than it can provide. That is why elements heavier than iron can only form in supernova explosions.

 

[Stephanus]

Iron cannot fuse it requires more energy than it can provide. That is why elements heavier than iron can only form in supernova explosions.

Or it fuses, but it absorbs more energy and trigger more fusion?

That is why elements heavier than iron can only form in supernova explosions.

The r and s process?

 

[Chronos]

Incorret. Iron cannot trigger more fusion, which is why heavier elements cannot form without a huge energy input -i.e., supernova.

 

[Stephanus]

Incorret. Iron cannot trigger more fusion, which is why heavier elements cannot form without a huge energy input -i.e., supernova.

I'm sorry, I would never dream to argue you with my tiny knowledge of astrophysics (and everything ). I just need confirmation to my doubt. The heavier elements are formed when the atoms collide outward from supernove explotion not inward before the start of the supernova, right?

 

[Chronos]

Basically correct, the phenomenol temperatures involved play a crucial role. to initiate what is called the r process

 

[Ken G]

Actually, were iron to fuse, it would remove heat, and that would indeed cause more fusion. The key point is, the core is self-gravitating, so has effectively a negative heat capacity. But what actually happens when the temperature rises is the iron nuclei get photodissociated before they fuse into anything else-- it's kind of the opposite of fusion, but it also removes heat and runs away.

 

[Stephanus]

Can I ask a question here, since we're at heat in it.
How are other elements lighter than iron created? Before the star goes supernova, there are 'onion' ring? And this is where the other element lighter than iron created? Not by supernova, but the elements are already there?
If it is true, are there actually elements lighter than iron created in the supernova process? (just out of curiousity)

 

[newjerseyrunner]

Yes, before the supernova, there are already layers of different elements. Heavier atoms will sink.

 

[Stephanus]

Yes, before the supernova, there are already layers of different elements. Heavier atoms will sink.

Are there actually elements lighter than iron created between the supernova explosion? Just out of curiousity.

 

[AgentSmith]

Yeah, thanks to Neil Degrasse Tyson.
Thanks for the link.

Actually we should thank Mike Brown, discoverer of several dwarf planets beyond Pluto in the Kuiper Belt. Author of How I Killed Pluto and Why It Had It Coming.

 

[Stephanus]

Actually we should thank Mike Brown, discoverer of several dwarf planets beyond Pluto in the Kuiper Belt. Author of How I Killed Pluto and Why It Had It Coming.

So, these planets are solar system member? And what about Pluto? Just another TNO object?

 

[newjerseyrunner]

They aren't planets as per the definition, but yes, they are members of the solar system. Pluto is a TNO, and it's also a dwarf planet. What differentiates a planet from a dwarf planet is whether or not it's cleared it's orbit of all other large objects. All of the planets are alone in their orbits other than their moons and some trojan asteroids, dwarf planets orbit the sun at the same distance as many other objects. There are five dwarf planets in our solar system, and six more candidates. Ceres is in the asteroid belt, the rest are at the edges of the solar system.

 

[Stephanus]

They aren't planets as per the definition, but yes, they are members of the solar system. Pluto is a TNO, and it's also a dwarf planet. What differentiates a planet from a dwarf planet is whether or not it's cleared it's orbit of all other large objects. All of the planets are alone in their orbits other than their moons and some trojan asteroids, dwarf planets orbit the sun at the same distance as many other objects. There are five dwarf planets in our solar system, and six more candidates. Ceres is in the asteroid belt, the rest are at the edges of the solar system.

So, Pluto and Neptune "share" their orbit at some points, but Pluto is a dwarf planet because it's smaller then Neptune, or Pluto is a dwarf planet because it's smaller then mercury? And Ganymede is not a planet because it doesn't orbit the sun directly.

 

[newjerseyrunner]

So, Pluto and Neptune "share" their orbit at some points,

No, Neptune has it's own orbit, it's not on the same plane. Neptune has cleared out it's neighborhood. Pluto shares it's orbit with lots and lots of comets.

but Pluto is a dwarf planet because it's smaller then Neptune, or Pluto is a dwarf planet because it's smaller then mercury?

No, it's a dwarf solely because it hasn't removed all of the matter around it. If you were to replace Mars with Pluto, it would be considered a planet then.

And Ganymede is not a planet because it doesn't orbit the sun directly.

Yes, if you put it where Mars is, it would be considered a planet because it's round and there aren't asteroids in it's orbit.

Size has nothing to do with it, if you put the Earth (the biggest rocky planet) deep out in the Oorb cloud, it would be considered a dwarf planet. The size of the planet's impact on it becoming a planet or a dwarf planet is only related to whether or not that mass is sufficient to throw everything else out of orbit, or eat it itself. I'm not even sure Jupiter would be a planet if it were in the Oort cloud, I don't think enough time has passed for it to clear everything from an orbit that big.

 

[rootone]

Pluto does not share an orbit with Neptune since it's orbit is about 17 degrees tilted out of the plane which all the other planets are in (with minor discrepancies).
Also it has a much more elongated eliptical orbit.
Although at it's closest to the Sun it is somewhat closer than Neptune is, it is not at an stage in a similar orbit.

I was going to add that the size is not a consideration in the revised classification, but njr has pointed that out already.

 

[D H]

There appears to be a meme arising here: As a PF discussion grows longer, the probability of a discussion of whether Pluto is or is not a planet approaches one.

Please keep this thread on topic.