Is this binary system animation correct ?

Discussion in 'Physics & Math' started by Singularity, Feb 22, 2007.

  1. Singularity Banned Banned

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    If the revolutions are correct then theres no way that blackhole should pullout matter from that star. Formation of blackhole doesn't mean that gravity increases. And if the BH can pull out matter then a normal star before its death too should be doing the same.

    What do u say ?
     
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  3. Dinosaur Rational Skeptic Valued Senior Member

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    Seems reasonable.

    You are correct. If the original planet or star could not pull material from a companion, collapse to a neutraon star or black hole would not increase the gravitational pull and would not result in having enough force to pull matter from the companion.
     
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  5. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    This assums that they are not moving closer together via radiation of gravity waves (or neither has been hit by third object that could it add some new negative angular momentum to the final two body system) and that neither was passing thru a thin residual atmosphere of the other, like a low altitude Earth satellite spiralling back to Earth. Anything that causes them to have less separation would increase the gravitational gradient rapidly as it is inverse cube, not square.

    My main fault with the animation, if we want to be "picky," is that the size of the small (black hole?) object seems to change more in cycle than the big one. this would imply that the big one is closer to their common center of mass (rotation point) yet I think they want the black hole (small object) to be the more massive one.
     
    Last edited by a moderator: Feb 22, 2007
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  7. Singularity Banned Banned

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    Interesting point,

    Now the question is if the massive star could pullout matter from the companion then why didnt it engulf the entire star instead or get merged with it ?
     
  8. Janus58 Valued Senior Member

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    It depends, stars evolve. The remaining star might have been a lot smaller before the BH formed, in fact, it may have even captured some of the material thrown off by the BH when it formed.

    Even if it didn't, stars can swell as they age; our own star will grow into a red giant during the course of its life cycle.

    If the remaining star expands enough, it will expand beyond the Roche Lobe. A little overly simply put, this is the point where gravitational attraction of the BH exceeds the surface gravity of the star.

    Thus you can have the situation where you can start with two stars in a binary system, neither one "suking matter from the other. One of the stars supernovas. Then, either due to the shock of the supernova, or due to its natural ages processes, the remaining star expands until it exceeds its Roche lobe, and you reach the situation shown in the animation.

    You don't even need a BH for this type of situation to develop, it can be a neutron star, a White Dwarf or a main sequence star(such as the situation with Beta Lyrae)

    The Binary system of Sirius A & B could someday form the white dwarf scenerio. B is the white dwarf. If A expands during its aging process, we will get this type of system.

    If this happens, Sirius could become a periodic nova. As the white dwarf accetes material from the "donor" star, it buids up on the surface. When enough accrues, it will set off a fusion explosion which causes the white dwarf to suddenly flare up brightly.
     
  9. Singularity Banned Banned

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    Thanks Janus58.

    Now i am wondering what happens when two stars swell and merge.
     
  10. Janus58 Valued Senior Member

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    I think it would be a fairly rare event for both stars to expand, as they would both have to reach that stage of their life cycle at the same time. One star though can expand to the point where it engulfs the other and forms what is called a contact binary.
     
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  12. Janus58 Valued Senior Member

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    The hotter an object is, the more radiation in the blue end of the spectrum it emits. More massive stars tend to be hotter since they burn their fuel faster. Main sequence stars are classified by their spectral type . hotter to cooler they go:

    O:30,000 - 60,000K Blue stars
    B:10,000 - 30,000K Blue-white stars
    A:7,500 - 10,000K White stars
    F: 6,000 - 7,500K Yellow-white stars
    G: 5,000 - 6,000K Yellow stars (like the Sun)
    K: 3,500 - 5,000K
     
  13. Singularity Banned Banned

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    Now i think the color of the star should have been red.
     

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