Objects in the universe

[Frank]

No that's not what I meant, and actually it's back-to-front.

As you increase the mass of a "normal" star (ie. a star composed of non-degenerate matter) you increase the energy output of the fusion reactor in the core. This energy produced is (broadly speaking) released from the core in the form of electromagnetic radiation, radiation which exerts a "pressure" on neutral or partialy ionized gases (eg. the stellar envelope). Eventually as you increase the stellar mass you reach the point at which the radiation pressure exterted by the core on the envelope of the star exceeds its self-gravity, and blows the envelope away... basically the star is so massive and hot it boils itself into space. From this we can infer that "normal" stars cannot do the things they do above a mass of ~150-200 Solar masses.

... and that leaves us with very many extremely-high energy things we have a very hard time grasping what can cause all that radiation. Some might be explained by the cores of galaxies, but most are frustratingly strange.

 

[AlNom]

very interesting.

 

[Dersaidin]

pffft, Antares is tiny - its like as big as my fist.

Oh wait...

 

[Geo]

Mars is that much smaller than Earth and Venus? Shame on me for not knowing that. I knew it was smaller, but not that much.

 

[KimB]

Glad you liked it. I was quite amazed at the scale difference of these objects. Im still having a hard time grasping some of these things are.

here is another example of scale, but in a different direction:
http://www.phrenopolis.com/perspective/atom/index.html
that web page is 11 miles wide!

Unfortunately, that's a bit bogus, because as far as we know, the electron has no actual size, but is a point particle. Now, if string theory is correct, that may reign in the size to be not quite point-like, but I have a suspicion the size would still be much smaller than what is displayed on that website.

The proton, however, does have a finite size, as it is a bound state of three quarks, just as an atom has a finite size that is defined by the size of the electron cloud that surrounds it.

 

[KimB]

... and that leaves us with very many extremely-high energy things we have a very hard time grasping what can cause all that radiation. Some might be explained by the cores of galaxies, but most are frustratingly strange.

I do have to wonder what precisely you're talking about, though.

For example, one class of GRB's is now believed to be explained by neutron star-neutron star or black hole-neutron star mergers.

 

[OpenGL guy]

Unfortunately, that's a bit bogus, because as far as we know, the electron has no actual size, but is a point particle. Now, if string theory is correct, that may reign in the size to be not quite point-like, but I have a suspicion the size would still be much smaller than what is displayed on that website.

The proton, however, does have a finite size, as it is a bound state of three quarks, just as an atom has a finite size that is defined by the size of the electron cloud that surrounds it.

But the electron cloud around an atom has no defined boundaries given that it's just where the electrons probably are.

 

[KimB]

But the electron cloud around an atom has no defined boundaries given that it's just where the electrons probably are.

Well, that's no less true for the proton or neutron, though. Anyway, for the Hydrogen atom it's pretty easy to define a boundary: just define the boundary by finding what distance from the center encloses x% of the probability distribution of the atom.

For more complex atoms things get much harder to deal with, as you have more electrons, and their probability distributions will fall off at different rates.

It becomes easier again when instead of looking at these probability distributions, you look at interactions. For example, it becomes very easy to ask what the size of an atom is in a solid or molecule, as you just look at the separation of the atoms within the solid or molecule.

This is, I believe, the definition of size that is applied to protons and neutrons.

 

[pcchen]

I think the point of that page is to demonstrate the emptiness inside an atom, not the size difference between proton and electrons (electrons has no size, as you said).

I remembered that a science magazine I've read in my elementary school days, it says if an atom is as big as the Tokyo dome (a baseball stadium), a proton is the size of a 100 Yen coin, sitting in the middle.

 

[K.I.L.E.R]

Sorry but a neutron star merging with another NS?
How can that be possible?
Wouldn't that cause the NS to go supernovae?

I do have to wonder what precisely you're talking about, though.

For example, one class of GRB's is now believed to be explained by neutron star-neutron star or black hole-neutron star mergers.

 

[nutball]

Sorry but a neutron star merging with another NS?
How can that be possible?

Binary neutron star systems are one end-point of the evolution of normal stellar binaries. The neutron starrs in such a system will gradually lose orbital angular momentum through, eg. gravitational radiation, which will cause them to sprial in towards each other. Eventually they'll merge. Here are some simulations a colleague of mine did recently.

Wouldn't that cause the NS to go supernovae?

The neutron stars are each already the result of a supernova. The NS-NS merger causes a gamma-ray burst, which is even more energetic than a supernova.

 

[Neeyik]

Sorry but a neutron star merging with another NS?
How can that be possible?
Wouldn't that cause the NS to go supernovae?

A supernova is the term used to describe the process when the core of a large red giant star collapses but produces no further fusion cycles, the end result being the outer layers of the star are ejected rather violently into space - neutron stars would obviously not do this. Anyway, it would be easier to explain how neutron stars merge if you could clear up why you think they can't.

Edit: Dang, too slow!

 

[K.I.L.E.R]

The reason I think it can't happen is because I don't even know what a neutron star is, I thought it was a large normal star that wasn't a red giant.

I can't believe that a star can still be a star after it supernovae'd. Makes very little sense.
Does it have something to do with a black dwarf collapsing into a black hole and pulling energy into it until it gets enough to become a star?

 

[Neeyik]

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/astcon.html#astcon

Best to start brushing up on some astrophysics then KILER!

 

[nutball]

The reason I think it can't happen is because I don't even know what a neutron star is, I thought it was a large normal star that wasn't a red giant.

It's the remnant of a supernova, typically ~twice the mass of our Sun, but ~10km in diameter (ie. extremely dense). It's supported by neutron degeneracy pressue. I'm sure Wikipedia will fill you in on the details.

I can't believe that a star can still be a star after it supernovae'd. Makes very little sense.

The Universe is a weird place!

Does it have something to do with a black dwarf collapsing into a black hole and pulling energy into it until it gets enough to become a star?

Ummm... no. There is an upper-limit on the mass of a neutron star though, above which the neutron degeneracy pressure can't support it against its own weight. Above this mass the neutron star would collapse to form a black-hole.

 

[K.I.L.E.R]

I'm going through this right now, I'm afraid I'm goimg to have to change my course into astrophysics in order to understand some of this stuff.
So far I gathered:

Let me attempt to break this down(Supernovae):

In fact, either the fission or fusion of iron group elements will absorb a dramatic amount of energy - like the film of a nuclear explosion run in reverse. If the temperature increase from gravitational collapse rises high enough to fuse iron, the almost instantaneous absorption of energy will cause a rapid collapse to reheat and restart the process. Out of control, the process can apparently occur on the order of seconds after a star lifetime of millions of years. Electrons and protons fuse into neutrons, sending out huge numbers of neutrinos. The outer layers will be opaque to neutrinos, so the neutrino shock wave will carry matter with it in a cataclysmic explosion.

Further:

In fact, either the fission or fusion of iron group elements will absorb a dramatic amount of energy - like the film of a nuclear explosion run in reverse. If the temperature increase from gravitational collapse rises high enough to fuse iron, the almost instantaneous absorption of energy will cause a rapid collapse to reheat and restart the process.

someElement >= Iron = absorbs energy under fusion at normal star energy dispertion.
Supernovae fixes this by overheating past what a normal star can do, iron becomes fused and process is restarted over and over again until a heavier element is formed and the current level of energy is inadequate to fuse the element.

Last part:

[...]Electrons and protons fuse into neutrons, sending out huge numbers of neutrinos. The outer layers will be opaque to neutrinos, so the neutrino shock wave will carry matter with it in a cataclysmic explosion.

Out layers of what?
From what I gather they are talking about outer layers of electrons and protons which cannot fuse to become neutrinos, so the neutrino shockwave formed from the smaller radius of electrons and protons will carry the outer protons and electrons very far outward which can then be used to form other stars, possibly planets?

Thanks for the info guys.

 

[London Geezer]

The Universe certainly is a very weird place. Everytime i hear about this sort of "trivia" kind of "cool info" such as a neutron star having double the mass of the Sun, but in a 10km diameter, my head starts dreaming... I mean, that's VERY dense. And i keep thinking, if i had a spoonful worth of "neutron star" (doesn't make sense, but u know what i mean), would it be so heavy to just fall through the spoon, the floor and into the earth? Would it have enough mass to have a strong gravitational pull? If so, would i "fall into it"?

I LOVE this kind of stuff...

 

[nutball]

Out layers of what?

The outer layers of the star I think they're referring to.

And i keep thinking, if i had a spoonful worth of "neutron star" (doesn't make sense, but u know what i mean), would it be so heavy to just fall through the spoon, the floor and into the earth? Would it have enough mass to have a strong gravitational pull?

Trivial hand-waving semi-factlet: 1 teaspoon of neutron star material has roughly the same mass as the whole human race.

 

[Acert93]

The Universe certainly is a very weird place. Everytime i hear about this sort of "trivia" kind of "cool info" such as a neutron star having double the mass of the Sun, but in a 10km diameter, my head starts dreaming... I mean, that's VERY dense. And i keep thinking, if i had a spoonful worth of "neutron star" (doesn't make sense, but u know what i mean), would it be so heavy to just fall through the spoon, the floor and into the earth? Would it have enough mass to have a strong gravitational pull? If so, would i "fall into it"?

Stop! You are going to scare K.I.L.E.R.!

Yeah, this stuff is enjoyable. Science work was always my favorite courses in high school and college. It is mind boggling how "empty" atoms are, and likewise the universe. Although I had never heard the figure before, but it does not sound unreasonable that if all the matter in the universe was tightly packed together (like a black hole) it could fit in the orbit of Mars.

It is pretty cool reading up on dark matter and energy as scientist learn more about this stuff. There is just so much we don't know... the universe is amazingly expansive.

 

[London Geezer]

The outer layers of the star I think they're referring to.


Trivial hand-waving semi-factlet: 1 teaspoon of neutron star material has roughly the same mass as the whole human race.

You didn't answer all the trivia questions!! what kind of scientist are you!!!

would it be so heavy to just fall through the spoon, the floor and into the earth? Would it have enough mass to have a strong gravitational pull? If so, would i "fall into it"?