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Thread: Magnetic mega-star challenges black hole theory

  1. #1 Magnetic mega-star challenges black hole theory 
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    Magnetic mega-star challenges black hole theory

    Source: http://news.yahoo.com/s/afp/20100818...pphu-container

    PARIS (AFP) – A neutron star with a mighty magnetic field has thrown down the gauntlet to theories about stellar evolution and the birth of black holes, astronomers reported on Wednesday.
    The "magnetar" lies in a cluster of stars known as Westerlund 1, located 16,000 light years away in the constellation of Ara, the Altar.
    Westerlund 1, discovered in 1961 by a Swedish astronomer, is a favoured observation site in stellar physics.
    It is one of the biggest cluster of superstars in the Milky Way, comprising hundreds of very massive stars, some shining with a brilliance of almost a million Suns and some two thousand times the Sun's diameter.
    The cluster is also, by the standards of the Universe, very young. The stars were all born from a single event just three and a half to five million years ago.
    Within Westerlund 1 is the remains of one of galaxy's few magnetars -- a particular kind of neutron star, formed from the explosion of a supernova, that can exert a magnetic field a million, billion times strong than Earth's.
    [Related: Massive black hole acts like cosmic magnifying glass]
    The Westerlund star which eventually became the magnetar must have been at least 40 times the mass of the Sun, according to the study, which appears in the research journal Astronomy and Astrophysics.
    If so, intriguing questions are raised.
    The mainstream assumption is that stars of between 10 and 25 solar masses go on to form neutron stars. But those above 25 solar masses produce black holes -- the light-gobbling gravitational monsters that are formed when a massive, dying star collapses in on itself.
    In that case, the magnetar's mother should have become a black hole because it was so big.
    But another alternative, say the authors, is that the star "slimmed" to a lower mass, enabling it to become a neutron star.
    How did this happen?
    The answer, says the paper, could lie in a binary system: the star that became the magnetar was born with a stellar companion.
    As the stars evolved, they began to interact, and the companion star, like a demonic twin, began to steal mass from the progenitor star.
    Eventually the progenitor exploded, becoming a supernova. The binary connection was sundered by the blast and both stars were ejected from the cluster, leaving just glowing remnants which are the magnetar, according to this theory.
    "If this is the case, it suggests that binary systems might play a key role in stellar evolution," said Simon Clark, who led the team, using the European Southern Observatory's Very Large Telescope in Paranal, Chile, to make the observations.
    A binary system could be "the ultimate cosmic 'diet plan' for heavyweight stars, which shifts over 95 percent of their initial mass," he said.


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  3. #2 Magnetic mega-star challenges black hole theory 
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    Magnetic mega-star challenges black hole theory

    Source: http://news.yahoo.com/s/afp/20100818...pphu-container

    PARIS (AFP) – A neutron star with a mighty magnetic field has thrown down the gauntlet to theories about stellar evolution and the birth of black holes, astronomers reported on Wednesday.
    The "magnetar" lies in a cluster of stars known as Westerlund 1, located 16,000 light years away in the constellation of Ara, the Altar.
    Westerlund 1, discovered in 1961 by a Swedish astronomer, is a favoured observation site in stellar physics.
    It is one of the biggest cluster of superstars in the Milky Way, comprising hundreds of very massive stars, some shining with a brilliance of almost a million Suns and some two thousand times the Sun's diameter.
    The cluster is also, by the standards of the Universe, very young. The stars were all born from a single event just three and a half to five million years ago.
    Within Westerlund 1 is the remains of one of galaxy's few magnetars -- a particular kind of neutron star, formed from the explosion of a supernova, that can exert a magnetic field a million, billion times strong than Earth's.
    [Related: Massive black hole acts like cosmic magnifying glass]
    The Westerlund star which eventually became the magnetar must have been at least 40 times the mass of the Sun, according to the study, which appears in the research journal Astronomy and Astrophysics.
    If so, intriguing questions are raised.
    The mainstream assumption is that stars of between 10 and 25 solar masses go on to form neutron stars. But those above 25 solar masses produce black holes -- the light-gobbling gravitational monsters that are formed when a massive, dying star collapses in on itself.
    In that case, the magnetar's mother should have become a black hole because it was so big.
    But another alternative, say the authors, is that the star "slimmed" to a lower mass, enabling it to become a neutron star.
    How did this happen?
    The answer, says the paper, could lie in a binary system: the star that became the magnetar was born with a stellar companion.
    As the stars evolved, they began to interact, and the companion star, like a demonic twin, began to steal mass from the progenitor star.
    Eventually the progenitor exploded, becoming a supernova. The binary connection was sundered by the blast and both stars were ejected from the cluster, leaving just glowing remnants which are the magnetar, according to this theory.
    "If this is the case, it suggests that binary systems might play a key role in stellar evolution," said Simon Clark, who led the team, using the European Southern Observatory's Very Large Telescope in Paranal, Chile, to make the observations.
    A binary system could be "the ultimate cosmic 'diet plan' for heavyweight stars, which shifts over 95 percent of their initial mass," he said.


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  4. #3  
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    Great Topic: I've written my own blog entry on the exact same topic.

    http://hicexsistoeverto.wordpress.co...-hole-mystery/

    Its prety awesome to think that such a magnetar exists.
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  5. #4 My two cents 
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    here are my two cents on the article....

    Size is not the only factor that plays part in black hole formation. Although theories related to Black Hole formation mention that stars with more than 25 solar masses have chances of becoming black hole... this doesn't mean this would happen for sure.

    A star with mass less than 10 solar mass can become a neutron star and then become black hole if it attracts mass from surroundings as much as it can't handle and collapses onto itself again.

    While a star with mass more than 30-40 solar masses can still end up as a neutron star if it loses too much mass before, during or right after supernova explosion.

    Black hole theory stays and this article in no way is presenting a NEW fact.

    What do you people think?
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  6. #5  
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    This star formed at the same time as others in the same cluster. So the fact that this star had already collapsed shows that it must have been more massive than the other stars that still exist there. Stars that are more than 25 times more massive than our Sun normally collapse to form black holes.
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  7. #6 my two cents 
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    here are my two cents on the article....

    Size is not the only factor that plays part in black hole formation. Although theories related to Black Hole formation mention that stars with more than 25 solar masses have chances of becoming black hole... this doesn't mean this would happen for sure.

    A star with mass less than 10 solar mass can become a neutron star and then become black hole if it attracts mass from surroundings as much as it can't handle and collapses onto itself again.

    While a star with mass more than 30-40 solar masses can still end up as a neutron star if it loses too much mass before, during or right after supernova explosion.

    Black hole theory stays and this article in no way is presenting a NEW fact.

    What do you people think?
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  8. #7  
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    Can someone merge the topic http://www.thescienceforum.com/Magne...ory-26132t.php into this topic? it somehow posted twice
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  9. #8  
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    Quote Originally Posted by Michael_Roberts
    This star formed at the same time as others in the same cluster. So the fact that this star had already collapsed shows that it must have been more massive than the other stars that still exist there. Stars that are more than 25 times more massive than our Sun normally collapse to form black holes.
    I agree that there is a general assumption that star with more than 25 solar masses become black hole... but even black hole theory suggests this isn't always the case.

    The star's neighborhood counts a lot... Think about a star of less than 10 solar masses which turn into a neutron star and have a very strong gravitational force... if its neighborhood is dense.. it may attract more mass to itself causing its density to increase... and at some point in time can collapse onto itself further forming a black hole...

    the other case is mentioned in the article i shared... a star can lose it mass to a binary star or maybe a nearby black hole or neutron star... maybe it loses most of its mass during supernova and doesn't remain with enough mass to turn into a black hole...

    Black hole formation doesn't only depend on size... it also depends on the composition of star... star's surroundings and other acting forces..

    This is my understanding which could be wrong... I am here to learn
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  10. #9  
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    Maybe try and find the work done by Dr Ben Ritchie of the Open University, I have my article here which you may find interesting. Would love to have comments too.

    http://hicexsistoeverto.wordpress.co...-hole-mystery/

    Also: Dr Negueruela of the University of Alicante in Spain, a co-author on the study, said that the mystery of the missing black hole might be explained if the progenitor star got rid “of nine-tenths of its mass before exploding as a supernova“. It has been speculated that one way of achieving this “mass reduction” would be if the progenitor star was part of a binary star system, and some of its mass was accreted onto the companion star. This would have allowed it to avoid the fate of becoming a black hole.

    Thanks!
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  11. #10  
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    Quote Originally Posted by Michael_Roberts
    Maybe try and find the work done by Dr Ben Ritchie of the Open University, I have my article here which you may find interesting. Would love to have comments too.

    http://hicexsistoeverto.wordpress.co...-hole-mystery/

    Also: Dr Negueruela of the University of Alicante in Spain, a co-author on the study, said that the mystery of the missing black hole might be explained if the progenitor star got rid “of nine-tenths of its mass before exploding as a supernova“. It has been speculated that one way of achieving this “mass reduction” would be if the progenitor star was part of a binary star system, and some of its mass was accreted onto the companion star. This would have allowed it to avoid the fate of becoming a black hole.

    Thanks!
    I have basically the same point as of Dr. Negueruela....
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  12. #11  
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    Quote Originally Posted by Aik Lamha
    Can someone merge the topic http://www.thescienceforum.com/Magne...ory-26132t.php into this topic? it somehow posted twice
    Done.
    Dishmaster
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