Inquiry about Sirius B

I have a question regarding Sirius B, in relation to this excerpt from Wikipedia:

This star is primarily composed of a carbon-oxygen mixture that was generated by helium fusion in the progenitor star.[6] This is overlaid by an envelope of lighter elements, with the materials segregated by mass because of the high surface gravity.[80] Hence the outer atmosphere of Sirius B is now almost pure hydrogen—the element with the lowest mass—and no other elements are seen in this star's spectrum

So let me get this straight, we are assuming that Sirius B is composed of Carbon-Oxygen from it's progenitor, yet based upon the light absorption lines, it appears to be pure hydrogen. They are saying that this hydrogen is just an envelope.

Is this common in white dwarfs? If so, id like to see some really concrete proof.

Sounds a lot like chromatography to me. The white dwarf is created in the collapse of a star due to lack of light fusion material. This leaves the heavier elements behind. The large difference in mass between H and C or O would easily "column" the lightest element at the surface. I suspect the carbon/oxygen interior is inferred by the size and age of the star determining the dominant fusion products formed during the birth of the dwarf star.It seems as though most light elements are formed in this fashion up to around Fe then the nuclear mass requires much more energetic conditions to form stable nuclei.Conditions like a supernova are largely responsible for the elements heavier than Iron.Granted I am no cosmologist but I do believe this is the accepted mechanism.
APB

segregated by mass because of the high surface gravity

Gases have been seperated due to intense gravity. Hydrogen is the first element in the periodic table (1 proton, 1 electron). The most "segregated" you can get in terms of atoms.

And then the heavier elements would reside underneath the hydrogen, so in effect you end up with onion-like layers of gases. With the Hydrogen being at the outer surface.

At least, this is what i can make sense of it, and it sounds logical to me. I am no scientist however;

Let's ask the Dogon Tribe, they should know.

reply to post by InsideYourMind


You both bring up good points, but this is what i was confused by:

White dwarfs are thought to be the final evolutionary state of all stars whose mass is not high enough to become a neutron star—over 97% of the stars in our galaxy.[5], §1. After the hydrogen–fusing lifetime of a main-sequence star of low or medium mass ends, it will expand to a red giant which fuses helium to carbon and oxygen in its core by the triple-alpha process. If a red giant has insufficient mass to generate the core temperatures required to fuse carbon, around 1 billion K, an inert mass of carbon and oxygen will build up at its center. After shedding its outer layers to form a planetary nebula, it will leave behind this core, which forms the remnant white dwarf.[6] Usually, therefore, white dwarfs are composed of carbon and oxygen.

It sounds like a typical white dwarf should have carbon/oxygen spectral lines, whereas Sirius B is not only the size of Earth, but by spectral lines, is pure hydrogen.

Perplexing for the moment...

Interesting - I hear that Sirius B gathers material from its companion star Sirius A as it comes to it's closest orbit then sheds that material when furthest away on its eliptical orbit.

Originally posted by ZeroUnlmtd
Let's ask the Dogon Tribe, they should know.

Im really glad you said this. Im laughing out loud

Originally posted by artistpoet
Interesting - I hear that Sirius B gathers material from its companion star Sirius A as it comes to it's closest orbit then sheds that material when furthest way in its eliptical orbit.

Ok this makes sense to me. I was just thinking about the two types of supernovae, the supergiant supernovae (type II i think) and type I which is when a white dwarf accretes matter from it's companion, say Sirius A. This would make sense then, if Sirius A has a Helium fusing core with Hydrogen envelopes, id wager a guess that it's almost certain that Sirius B is accreting that Hydrogen, hence why all we pick up is Hydrogen on Sirius B.

Now even more pressing, how close is Sirius B to the point of Type 1 supernova?

Originally posted by xacto

Originally posted by artistpoet
Interesting - I hear that Sirius B gathers material from its companion star Sirius A as it comes to it's closest orbit then sheds that material when furthest way in its eliptical orbit.

Ok this makes sense to me. I was just thinking about the two types of supernovae, the supergiant supernovae (type II i think) and type I which is when a white dwarf accretes matter from it's companion, say Sirius A. This would make sense then, if Sirius A has a Helium fusing core with Hydrogen envelopes, id wager a guess that it's almost certain that Sirius B is accreting that Hydrogen, hence why all we pick up is Hydrogen on Sirius B.

Now even more pressing, how close is Sirius B to the point of Type 1 supernova?

edit on 24-1-2012 by xacto because: (no reason given)

As far as I know not all stars supernova the same way. Sirius B is considered dead in astronomical terms.
Massive stars can super nova and create black holes - so they say - I guess Betelguese would fit that category of stars

reply to post by xacto


Holy #e guys, i think ive stumbled accross some pretty basic knowledge that just hasn't been focused upon, check this out:

Supernovae are classified as Type I if their light curves exhibit sharp maxima and then die away smoothly and gradually. The model for the initiation of a Type I supernova is the detonation of a carbon white dwarf when it collapses under the pressure of electron degeneracy. It is assumed that the white dwarf accretes enough mass to exceed the Chandrasekhar limit of 1.4 solar masses for a white dwarf. The fact that the spectra of Type I supernovae are hydrogen poor is consistent with this model, since the white dwarf has almost no hydrogen. The smooth decay of the light is also consistent with this model since most of the energy output would be from the radioactive decay of the unstable heavy elements produced in the explosion.

And

α CMa B Mass 0.978[6] M☉

The hydrogen aspect is still throwing me off, but in terms of mass, it would seem that if it was based off mass this white dwarf is fairly close to supernova. On the other hand, if a white dwarf happens to be in a binary where the other star is offering up pure hydrogen, maybe it makes an entirely new object, not even a white dwarf by definition?

reply to post by xacto


I find it impossible to come to a conclusion on this but it is great food for thought.
Perhaps Sirius B has already gone super nova and drwn Sirius A into it's orbit - Some massive stars create a Black Hole when they go super nova - Betelguse would be a good example of such a star - Or look at Etna Carina which is pulsing on the point of popping. I read in an Astronomy mag many years ago that in the Crab supernove which is very close - that there are two remnant stars locked within a sort of elctro magnetic cage which nothing penetrates - from this cage though it emits radio waves perpendicular to its orbital plane - much like a galaxy black hole. But I am no expert that is for sure

reply to post by xacto


The material Sirius B gathers from Sirius A is shed - some say toward the Sun. then it goes through the same process in an eleptical cycle of 60 years

reply to post by artistpoet


The diagram you posted does not fit the Sirius system - if it did Sirius A would be a red giant yet it is millions of years away from becoming a red giant as is our Sun which is mid way through its cycle

Have you considered Sirius C? .. And what effect it sould have on your Hypothisis?

Originally posted by gLuEBoY
Have you considered Sirius C? .. And what effect it sould have on your Hypothisis?

Sirius C is supposedly a planet which was once dEtected but then dismissed yet I read recently some Astro scientists have saiD that they detect another body around Sirius A - meaning Sirius C

Originally posted by xactoThe hydrogen aspect is still throwing me off, but in terms of mass, it would seem that if it was based off mass this white dwarf is fairly close to supernova.

Not really. The Chandrasekhar limit is 1.38 solar masses. Sirius B is 0.978 solar masses. It would have to gain 41% more mass to reach the Chandrasekhar limit that would cause a supernova.

reply to post by nataylor


This is of course assuming that the threshold limit based off our estimations is absolute.

The ideas of Sirius C are certainly fascinating, as per my other thread inquiring about the lack of the Kepler project www.abovetopsecret.com...

Originally posted by artistpoet
reply to post by artistpoet

 

The diagram you posted does not fit the Sirius system - if it did Sirius A would be a red giant yet it is millions of years away from becoming a red giant as is our Sun which is mid way through its cycle

edit on 24-1-2012 by artistpoet because: typos

I made the connection as well. My thinking is that maybe we don't know about supernovae and binary interaction as well as we should, yet here we have a fine specimen that is right next door. Surely we can observe it with all of our best tools and minds and learn much about it!

Originally posted by xacto
Is this common in white dwarfs? If so, id like to see some really concrete proof.

Wel as you know, Starfleet ship have visited several dozen white dwarfs within 100 light years of Sol in the past few decades, and we have detailed spectral analysis available in all starfleet libraries ......

Oh, wait, it's still 2012. B*gger. Guess you're gonna have to wait.

Originally posted by xacto

Originally posted by artistpoet
reply to post by artistpoet

 

The diagram you posted does not fit the Sirius system - if it did Sirius A would be a red giant yet it is millions of years away from becoming a red giant as is our Sun which is mid way through its cycle

edit on 24-1-2012 by artistpoet because: typos

I made the connection as well. My thinking is that maybe we don't know about supernovae and binary interaction as well as we should, yet here we have a fine specimen that is right next door. Surely we can observe it with all of our best tools and minds and learn much about it!

I agree we know so little really - there are so many combinations of stars and systems.
Regarding Sirius system - It has often baffled me why we have not researched and aimed our sights to this very special and close system more.