Star Formation

[harry]

Hello All

I want to know why some cores of stars are 10^2 and some 10^30 density.

It is so interesting to find out why some star cores are of atomic structure and some of subatomic and some sub-subatomic.

Also what is the process involved with a Nova and supernova and do they both leave star cores behind.

Look my information out of my head is limited and therefore I rely on images and notes. See the following.

Now if these notes and images are themselves limited and you have more info please help.



images
http://www.ipac.caltech.edu/2mass/galle ... _ysos.html

http://antwrp.gsfc.nasa.gov/cgi-bin/apo ... +Formation

notes
http://www-astronomy.mps.ohio-state.edu ... imass.html

http://www-astronomy.mps.ohio-state.edu ... rnova.html

http://observe.arc.nasa.gov/nasa/space/ ... th_4a.html

http://www.stsci.edu/stsci/meetings/shst2/ballyj.html

[Qev]

Hello All

I want to know why some cores of stars are 10^2 and some 10^30 density.

Other than black holes, I think most stellar remnants max out around 10^18kg/m^3 or so. Beyond that you end up with a black hole, I would think.

It is so interesting to find out why some star cores are of atomic structure and some of subatomic and some sub-subatomic.

That all depends on core temperature and pressure.

Also what is the process involved with a Nova and supernova and do they both leave star cores behind.

A nova is a white dwarf star with a binary companion star, where material from the envelope of the companion accumulates on the surface of the white dwarf. Once enough material accumulates, the pressure and temperature on the surface of the white dwarf is sufficient to trigger a flash of hydrogen fusion across the surface, leading to a dramatic, temporary increase in luminosity. After the eruption, the white dwarf and companion star remain, often to begin the process all over again.

Supernovae come in various types. The two I'm familiar with are Type Ia and Type II supernovae.

Type II are caused by the core collapse of dying high-mass stars, who have built up an inert iron core and can no longer sustain fusion reactions. The core rapidly collapses (at a quarter light speed!), rebounds, and the shockwave caused by this (and the subsquent neutrino pulse as the core converts to a neutron star) blasts the star apart. This leaves behind a neutron star, or in very high-mass stars, a black hole.

Type Ia are very much like novae in their cause of origin. Again, it's a white dwarf star accumulating matter from a companion. However in these cases, the white dwarf is accreting matter fast enough that it can't burn it off in a nova explosion. The mass of the white dwarf increases to the point where it exceeds the Chandrasekhar limit; this sets off a chain reaction causing the entire white dwarf to undergo flash-fusion, detonating it. The white dwarf in this case is completely destroyed.

[harry]

Hello Qev

Excuse the writing i have added more info for those who may want to understand the processes.

I agree with your writing.

But! by now you would know me and I keep on questioning. Years gone by my science teacher, I think went crazy because of my questions. Smile.

Anatomy of a Classical Nova outburst. As qev has stated.

http://observe.arc.nasa.gov/nasa/space/ ... th_4a2.htm
http://observe.arc.nasa.gov/nasa/space/ ... th_4a.html

The classical nova outburst arises as follows:

A white dwarf consisting of elements heavier than hydrogen, such as carbon and oxygen, accretes hydrogen-rich matter from a close companion star.


The matter passes through an accretion disk that surrounds the white dwarf, before spiraling down onto the white dwarf.

This transfer of matter from the companion star to the white dwarf is a continuous process: Fresh matter arrives at the outer edge of the accretion disk from the companion star, spirals through the disk, and accretes onto the white dwarf.


When about 1/100,000 of a solar mass of hydrogen-rich matter has been accreted, the temperature and density at the base of the accreted matter become so severe that a nuclear explosion is triggered and the white dwarf's surface layer is ejected at speeds of about 500 miles/second or greater (2 million miles per hour or greater).


The explosion and ejection are accompanied by an intense brightening. Hence, the name nova, meaning "new" (i.e., the star becomes visible across interstellar distances).


Maximum brightness lasts only a few days. The brightness then diminishes and, in the course of several months, returns to the pre-outburst level.


Mass transfer and accretion then resume until another nova outburst occurs.

Dwarf nova
quote:

"A white dwarf accretes hydrogen-rich matter from a close companion star via an accretion disk.


However, unlike in classical novae, the matter does not spiral continuously through the accretion disk to impact on the white dwarf.

For reasons that are not well understood, the matter accumulates in the accretion disk until an instability develops and the entire accretion disk crashes down onto the white dwarf. Large amounts of gravitational energy are released. There is no nuclear explosion.


The released energy heats the white dwarf surface and temporarily brightens the star, which we observe as a dwarf nova. The term "dwarf" indicates that the brightening is less than that in classical novae."

Supernova ejection

Supernova (II)
http://observe.arc.nasa.gov/nasa/space/ ... th_3a.html
http://observe.arc.nasa.gov/nasa/space/ ... acont.html

Iron Core Collapse

Gravity, which up to now was balanced by the outward force of the pressure, decisively gains the upper hand and the iron core collapses.


In less than a second, the core collapses from a size of about 5,000 miles to one of about a dozen miles, and an enormous amount of energy is released. This collapse happens so fast that the star's outer layers have no time to react and participate in it.


The amount of energy that is released during core collapse is truly gigantic -- it is equivalent to the energy produced by 100 stars like the Sun during their entire lifetimes of more than 10 billion years!


Most of the energy released during the collapse of the iron core is carried off into space by elusive particles called neutrinos. A small fraction of the energy is deposited in the lower layers of the envelope surrounding the core and triggers the supernova explosion.

"The result of these events is a compact stellar remnant and a rapidly expanding gaseous shell.

The stellar remnant is a neutron star or a black hole.

The expanding gaseous shell plows into the surrounding interstellar medium, and pushes, compresses, and intermingles with it. Such regions of the interstellar medium are known as supernova remnants."

Supernova (I)

http://observe.arc.nasa.gov/nasa/space/ ... th_4c.html
quote:

"The white dwarf is more massive than the Sun, consists predominantly of carbon and oxygen, and accretes matter from its companion relatively rapidly. Any nova outbursts that occur on the white dwarf are relatively weak and eject only little matter. Consequently, the white dwarf grows in mass:

When the accretion has raised the white dwarf's mass to the critical mass of about 1.4 solar masses, the density and temperature in the star's center become so severe that carbon starts burning explosively.


Within roughly one second, the burning front moves all the way to the surface, making the entire white dwarf one huge nuclear fireball.


The entire star explodes and destroys itself. There is no stellar remnant.


All of the star's matter -- namely, the products of the nuclear burning (iron, nickel, silicon, magnesium, and other heavy elements) plus unburned carbon and oxygen -- are ejected into space at speeds ranging from about 6,000 to 8,000 miles/second (20 to 30 million miles/hour).


Unlike supernovae of type II, the matter ejected in type I supernovae consists almost entirely of the heavier elements. There is no, or almost no, hydrogen."

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The question is this.

Can a normal star without a companion have either Nova, classical or dwarf.

[Qev]

Can a normal star without a companion have either Nova, classical or dwarf.

Nope! Without a stellar companion, there's no source of infalling material to trigger a nova. Things like interstellar gas clouds wouldn't be dense enough to accumulate significant quantities on the surface of a white dwarf, I don't think. Maybe if it plowed straight through a Bok globule or something...

[Pete]

At the risk of threadjacking: I had never heard of Bok globules before due to apparently missing April 20th's APOD mentioning them. They're cold, dark molecular or dust clouds that are condensing to form stars.

Something new every day. Thanks!

[harry]

Hello All

Thank you Qev you read my mind.

As for Bok Globules

http://antwrp.gsfc.nasa.gov/apod/ap961229.html

Bok globules, named after astronomer Bart Bok who studied them extensively, are small dark clouds made of gas and dust that are typically condensing to form a star or stars.

Info link
http://articles.adsabs.harvard.edu/cgi- ... .108..612Y
http://dsnra.jpl.nasa.gov/origins/nyt.html

Other images

http://antwrp.gsfc.nasa.gov/apod/ap030127.html
http://antwrp.gsfc.nasa.gov/apod/ap060420.html

This is so interesting, a few more years of this and I may get the hang of it.

Its so scary that the more I learn the more I find that I do not know.
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So! we can get nova by
1) Companion star
2) If the star goes through a Bok Globule

What about other ways?

[Qev]

Well, don't take the Bok globule thing too seriously. I'm hardly an astrophysicist; I don't see why it couldn't happen, but that doesn't mean I know what I'm talking about. The odds against it happening, also, are probably... astronomical.

[harry]

Hello Qev

I know, but this is a friendly discusssion no rocks.

At least you have ideas that are on track.

[harry]

Hello All

Here is some recent info on sun's workings. This info will change the standard model as we know it.

I tried to copy parts of it, bu! I was unable.

http://www.omatumr.com/papers.html

http://www.omatumr.com/abstracts2003/jf ... uidity.pdf
http://www.omatumr.com/abstracts2005/Is ... ration.pdf
http://www.omatumr.com/abstracts2006/Nu ... Cosmos.pdf
http://www.omatumr.com/abstracts2006/OC ... OCycle.pdf

[harry]

Hello All

Star formation near the centre of the Milky Way.

http://www.space.com/scienceastronomy/a ... 20111.html

Chandra Reveals Features of 30-year Galactic Mystery

The Chandra X-ray Observatory has captured the sharpest images yet of a mysterious X-ray-emitting ridge that lurks within the center of our Milky Way galaxy.

This led Zadeh and his team to theorize that low-energy cosmic rays must have bombarded, and thus heated, a cloud of cold gas 1 million times the mass of the Sun. The collision would have produced the X-ray emission of the galactic ridge.

Earlier explanations of the ridges origin have focused on rather dramatic scenarios, such as 100 million-degree gases being constantly replenished by an unknown source, or an energetic explosion at the galactic center that may have occurred 300 years ago

"The bombardment of the giant clouds by low-energy cosmic rays increases their temperature and degree of ionization, two key parameters that determine the ability of interstellar clouds to form stars," explained another of the project's scientists, Mark Wardle of the University of Sydney, Australia.

[harry]

Hello All

If I repeat any links,,,,,,,,,,,,,,,,,,,,,,,ooops

I thought this link maybe of interest to some


Star formation
http://fire.biol.wwu.edu/trent/alles/Star_Formation.pdf

[Dr. Skeptic]

I quickly read over this paper, visually great but it is written with the scientific mastery of a junior high student: clumpy, chain of motorboats ...

More unscientific, unsubstanciated, wildly speculative, no foundational science, I knew I shouldn't have wasted my time, - - - - web trash.

[harry]

Hello Dr Skeptic

Sometimes links are not for all. Its OK for the general public. Some parts I do not agree with, but! thats me


But! if you have something to offer, please provide it rather than sitting on the fence and acting like my wife.

[Nereid]

Well, there is at least one other way to make an 'isolated' star go nova ... have it collide with another star!

This happens very, very rarely in our neck of the Milky Way woods, but in the heart of rich, massive globular clusters, it happens .... enough to give rise to a class of stars called 'blue stragglers'.

IIRC, there's a very nice finding, supporting current models for stellar collision rates, at the hearts of big globular clusters, reported recently on an ESO site ... from 47 Tuc (the second brightest globular cluster in the southern sky, if I'm not mistaken). If anyone's interested, I'll see if I can dig it up (along with a reference to a nice Scientific American article, a few years ago, on modelling collisions between two stars).

[astro_uk]

47 Tuc is just about the most studied GC there is. One of the more interesting things people are doing now is measuring th radial velocities of individual GC stars to search for intermediate mass BHs in them. These are BHs in the range 20Msun < M < 1000Msun and can be thought of as filling in the gap of masses of BHs between stellar mass BHs and supermassive BHs at the centre of galaxies. I think only G1 and Omega Cen have evidence that looks slightly believeable at the moment though.

[harry]

Hello Neried

I would like to see that info.

=====================================

At this moment I'm looking into what possible triggers that are involved in super novae and novae.

[Nereid]

Stellar Vampires Unmasked

What are "blue stragglers"?

APOD, 8 August, 2003

[Dr. Skeptic]

Hello Dr Skeptic

Sometimes links are not for all. Its OK for the general public. Some parts I do not agree with, but! thats me


But! if you have something to offer, please provide it rather than sitting on the fence and acting like my wife.

If I can stop you from posting non-science trash on this forum I'll be offering the most important service of all.

[Nereid]

... is "When Stars Collide", by Michael Shara. It appeared in the November 2002 issue, and is available online (for a price).

[craterchains]

sitting on the fence with Dr. Skeptic and Harry's wife, , ,

Norval

[harry]

Dr Skeptic

Keep your focus on the topics and not on the people.

Trash ,,,,,,,,,,,what is trash

So far you have proven nothing, but! comments that go around in circles.

I have tried to be unconventional for good reasons.

Yes we could all agree on standard models.

But! many cosmologists are moving away from these standard models for good reasons.

New observations and new methods of looking at the universe has provided unconventional options in this day an age.

So keep your trash bin, aside for now.

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Hello craterchains,,,,,,,,,,,,,,,you make me smile

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Thank you for the links Nereid
http://www.eso.org/outreach/press-rel/p ... 37-06.html

They discovered that six of these Blue straggler stars contain less carbon and oxygen than the majority of these peculiar objects. Such an anomaly indicates that the material at the surface of the blue stragglers comes from the deep interiors of a parent star [2]. Such deep material can reach the surface of the blue straggler only during the mass transfer process occurring between two stars in a binary system. Numerical simulations indeed show that the coalescence of stars should not result in anomalous abundances.

Why not from fusion within the stars?

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http://curious.astro.cornell.edu/questi ... number=297

In their explanation they do not mention the possible properties of the core the main player in star formation but! not the only one.

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http://antwrp.gsfc.nasa.gov/apod/ap030808.html

http://www.aas.org/publications/baas/v3 ... 96/265.htm

[41.06] The Amazing Blue Stragglers in the Core of the Galactic Globular Cluster NGC 6397
J.F. Sepinsky, R.A. Saffer, C.S. Pilman (Villanova University), G. DeMarchi, F. Paresce (ESO)

Blue Straggler Stars (BSS) in Galactic globular clusters (GCs) are thought to be formed via as-yet poorly understood interactions in binary star systems in the dense cluster cores, perhaps by the merger of two (or possibly more) stars into a single star. These stars reside on the Main Sequence beyond the cluster turn-off. NGC 6397 has six bright BSS in the cluster core, two of which are too blue, and too hot according to a model atmosphere analysis, to have been formed from mergers of only two lower-mass stars. If pure merger products, they must both have been formed by the coalescence of at least {\em three} lower mass stars. Alternatively, and more likely, is that their excess blue light is due to the presence of hitherto undetected compact hot companions, implying that they formed in heirarchical multiple star systems, or have perhaps captured an additional star at some point in their lifetimes. Other possible formation scenarios include mass accretion from their (presumed) binary companions. In this display paper, we present the results of our spectroscopic analysis of HST FOS spectra of the six BSS, namely masses and rotation rates, and we discuss the implications of our findings for their evolutionary history.

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[Nereid]

[snip]

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Thank you for the links Nereid
http://www.eso.org/outreach/press-rel/p ... 37-06.html

They discovered that six of these Blue straggler stars contain less carbon and oxygen than the majority of these peculiar objects. Such an anomaly indicates that the material at the surface of the blue stragglers comes from the deep interiors of a parent star [2]. Such deep material can reach the surface of the blue straggler only during the mass transfer process occurring between two stars in a binary system. Numerical simulations indeed show that the coalescence of stars should not result in anomalous abundances.

Why not from fusion within the stars?

===========================================
[snip]

I don't understand your question, harry - could you clarify please?

[Dr. Skeptic]

Dr Skeptic

Keep your focus on the topics and not on the people.

Trash ,,,,,,,,,,,what is trash

So far you have proven nothing, but! comments that go around in circles.

I have tried to be unconventional for good reasons.

Yes we could all agree on standard models.

But! many cosmologists are moving away from these standard models for good reasons.

New observations and new methods of looking at the universe has provided unconventional options in this day an age.

So keep your trash bin, aside for now.

I'm sorry if you do not/cannot understand my rebuttals to your non-science postings, but I am also not responsibility for your education.

When I was about five years old I thought I could take all the cleaning supplies from under the sink and if I mixed them Just right I could create a bran new element and be famous forever - to say the least, my education fell well short of the understanding needed for synthesizing elements.

Harry you are still playing with cleansers. I can detect the flaws in the theories you post by the first paragraph and not because I have a bias to one theory or another - because I have learned and understand how the pieces of the universe work together.

Put the cleaners back under the sink and open a "real book" and get away from the tabloid science, it will get you nowhere.

[Doum]

I agree with Dr. Septic,

What your saying is inbeleivable. Its your right to beleive it anyway. The problem is that you want everyone that write sumthing on the BigBang or real science to stop beleiving it just because you say so. You want them to beleive your imagination (As if it was a religion you want to create.). All the time you interfere in a post saying BigBang didnt happen. Some young here who want to learn true science migth think that what you say is true and then fail their exam at school cause they beleive you were saying the truth. You are doing wrong by giving your idea all the time and each time sumone talk bigbang (You always say BigBang never happen.). Now we know your opinion so stop bothering us about it. If people come here, its to talk about proof science, not harry's belief. What the other in here do, is to talk science to all and to you. It's you who seem to not want true science to exist. No they wont keep their focus just on topics, they will keep it on you too and say to all that you are wrong. Its the right thing to do. They also have the right to be stubborn. Go create your own website and talk to yourself.

[harry]

Hello Dowm

I think you have a problem

Go get help

If I express my ideas, thats fine. If you do not like those ideas thats fine.

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Dr Skeptic

If you do not like my comments, why discuss them with me. Go and discuss them with someone else.

You have your ideas and you write so well and convincing. People will follow you until they know where they are heading.

As for my ideas. Name one that you think against.