Posted on 08/18/2010 10:06:11 AM PDT by decimon
Using ESO’s Very Large Telescope, European astronomers have for the first time demonstrated that a magnetar — an unusual type of neutron star — was formed from a star with at least 40 times as much mass as the Sun. The result presents great challenges to current theories of how stars evolve, as a star as massive as this was expected to become a black hole, not a magnetar. This now raises a fundamental question: just how massive does a star really have to be to become a black hole?
To reach their conclusions, the astronomers looked in detail at the extraordinary star cluster Westerlund 1 [1], located 16 000 light-years away in the southern constellation of Ara (the Altar). From previous studies (eso0510), the astronomers knew that Westerlund 1 was the closest super star cluster known, containing hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two thousand times the diameter of the Sun (as large as the orbit of Saturn).
“If the Sun were located at the heart of this remarkable cluster, our night sky would be full of hundreds of stars as bright as the full Moon,” says Ben Ritchie, lead author of the paper reporting these results.
Westerlund 1 is a fantastic stellar zoo, with a diverse and exotic population of stars. The stars in the cluster share one thing: they all have the same age, estimated at between 3.5 and 5 million years, as the cluster was formed in a single star-formation event.
A magnetar (eso0831) is a type of neutron star with an incredibly strong magnetic field — a million billion times stronger than that of the Earth, which is formed when certain stars undergo supernova explosions. The Westerlund 1 cluster hosts one of the few magnetars known in the Milky Way. Thanks to its home in the cluster, the astronomers were able to make the remarkable deduction that this magnetar must have formed from a star at least 40 times as massive as the Sun.
As all the stars in Westerlund 1 have the same age, the star that exploded and left a magnetar remnant must have had a shorter life than the surviving stars in the cluster. “Because the lifespan of a star is directly linked to its mass — the heavier a star, the shorter its life — if we can measure the mass of any one surviving star, we know for sure that the shorter-lived star that became the magnetar must have been even more massive,” says co-author and team leader Simon Clark. “This is of great significance since there is no accepted theory for how such extremely magnetic objects are formed.”
The astronomers therefore studied the stars that belong to the eclipsing double system W13 in Westerlund 1 using the fact that, in such a system, masses can be directly determined from the motions of the stars.
By comparison with these stars, they found that the star that became the magnetar must have been at least 40 times the mass of the Sun. This proves for the first time that magnetars can evolve from stars so massive we would normally expect them to form black holes. The previous assumption was that stars with initial masses between about 10 and 25 solar masses would form neutron stars and those above 25 solar masses would produce black holes.
“These stars must get rid of more than nine tenths of their mass before exploding as a supernova, or they would otherwise have created a black hole instead,” says co-author Ignacio Negueruela. “Such huge mass losses before the explosion present great challenges to current theories of stellar evolution.”
“This therefore raises the thorny question of just how massive a star has to be to collapse to form a black hole if stars over 40 times as heavy as our Sun cannot manage this feat,” concludes co-author Norbert Langer.
The formation mechanism preferred by the astronomers postulates that the star that became the magnetar — the progenitor — was born with a stellar companion. As both stars evolved they would begin to interact, with energy derived from their orbital motion expended in ejecting the requisite huge quantities of mass from the progenitor star. While no such companion is currently visible at the site of the magnetar, this could be because the supernova that formed the magnetar caused the binary to break apart, ejecting both stars at high velocity from the cluster.
“If this is the case it suggests that binary systems may play a key role in stellar evolution by driving mass loss — the ultimate cosmic ‘diet plan’ for heavyweight stars, which shifts over 95% of their initial mass,” concludes Clark. Notes
[1] The open cluster Westerlund 1 was discovered in 1961 from Australia by Swedish astronomer Bengt Westerlund, who later moved from there to become ESO Director in Chile (1970–74). This cluster is behind a huge interstellar cloud of gas and dust, which blocks most of its visible light. The dimming factor is more than 100 000, and this is why it has taken so long to uncover the true nature of this particular cluster.
Westerlund 1 is a unique natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Milky Way live and die. From their observations, the astronomers conclude that this extreme cluster most probably contains no less than 100 000 times the mass of the Sun, and all of its stars are located within a region less than 6 light-years across. Westerlund 1 thus appears to be the most massive compact young cluster yet identified in the Milky Way galaxy.
All stars so far analysed in Westerlund 1 have masses at least 30–40 times that of the Sun. Because such stars have a rather short life — astronomically speaking — Westerlund 1 must be very young. The astronomers determine an age somewhere between 3.5 and 5 million years. So, Westerlund 1 is clearly a “newborn” cluster in our galaxy. More information
The research presented in this ESO Press Release will soon appear in the research journal Astronomy and Astrophysics (“A VLT/FLAMES survey for massive binaries in Westerlund 1: II. Dynamical constraints on magnetar progenitor masses from the eclipsing binary W13”, by B. Ritchie et al.). The same team published a first study of this object in 2006 (“A Neutron Star with a Massive Progenitor in Westerlund 1”, by M.P. Muno et al., Astrophysical Journal, 636, L41).
The team is composed of Ben Ritchie and Simon Clark (The Open University, UK), Ignacio Negueruela (Universidad de Alicante, Spain), and Norbert Langer (Universität Bonn, Germany, and Universiteit Utrecht, the Netherlands).
The astronomers used the FLAMES instrument on ESO’s Very Large Telescope at Paranal, Chile to study the stars in the Westerlund 1 cluster.
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”. Links
* Research paper * More information: Black Hole Press Kit
Contacts
Simon Clark The Open University UK Tel: +44 207 679 4372 Email: jsc@star.ucl.ac.uk
Ignacio Negueruela Universidad de Alicante Alicante, Spain Tel: +34 965 903400 ext 1152 Email: ignacio.negueruela@ua.es
Richard Hook ESO, La Silla, Paranal and E-ELT Press Officer Garching bei München, Germany Tel: +49 89 3200 6655 Email: rhook@eso.org
About the same amount of mass that you’ll find between the average liberal’s ears.
I forgot, I miss - spelled huge.
Deval Patrick is a hugh Mass Hole
Obama can provide estimates of up to a trillion.
How Much Black Makes a Mass Hole?
Glad you fixed that. Spelling is a series matter.
” Obama can provide estimates of up to a trillion. “
Which will be promptly debunked by the CBO - as soon as it’s too late to do anything about it....
Maybe Dark matter acts as a catalyst in neutron stars for converting them into black holes by neutralizing the strong nuclear force or something.
......or something.
I love astronomy. You can make up whatever crap you want, and use it as factual support for your theories.
Like the argument that this magnetar was part of a binary system, and that they split in a violent escape from the cluster.
While it explains where the other half of the pair went, it doesn’t explain why the magnetar did not leave the cluster.
Then there is the assumption that Mass can be inferred from Size without taking density into consideration. Maybe the magnetar had a different density.
I also like the fact that while observations and deductions were based on visual information, this cluster is one of the hardest clusters to ‘visually’ see.
Plus,what makes anyone sure black holes even exist?
Perhaps you have some theories you’d like to advance for
the stellar phenomena?
Or are you just going to throw crap?
You can do the math yourself. Past a certain density, the mass will collapse in on itself.
As for 95 percent mass loss in a binary system, ever hear of Roche limits. Close binaries can and do share mass.
Three, as for the star which was tossed, my thought is that the binary is the magnetar, and the original companion was tossed by the force of the supernova explosion.
Thanks for the laughter, needed that! Memories of earlier posters.
See? Another unproven assumption.
Past a certain density, the mass will collapse in on itself.
Past, as in 'above' a certain density?
Given that mass is a constant (less the amount being consumed daily), if the size of the star increased, the density would decrease. I could see how a decrease in density would cause the collapse in on itself.
If we go with an 'increase' in density, I assume you are positing that the increase in gravity would produce the collapse.
If the density and size are increasing, the star must be intaking mass, instead of giving it off (as energy in the EM spectrum). This makes no physical nor logical sense.
As for 95 percent mass loss in a binary system, ever hear of Roche limits. Close binaries can and do share mass.
Please. Children may be reading this.
Three, as for the star which was tossed, my thought is that the binary is the magnetar, and the original companion was tossed by the force of the supernova explosion.
Yes, but was it a legal divorce?
Are you saying the magnetar has a new companion?
About a trillion dollars in deficit stimulus spending
Graceg 's theory is just as logical, and provable, and backed by the same facts as the one in this article.
Unproven? I’ve done the math. You can do it too.
The best way to prove something is to do it yourself.
“Given that mass is a constant (less the amount being consumed daily), if the size of the star increased, the density would decrease. I could see how a decrease in density would cause the collapse in on itself.”
Sigh.
You know anything about hydrostatic equilibrium? Stars aren’t solid. The only thing that keeps them out is the outward pressure of the fusion reactions from the core. Think of a balloon.
What happens is that as the star exhausts it’s fuel, the composition changes, from Hydrogen to helium to heavier elements, all the way to iron. Iron actually absorbs energy in nuclear fusion, so it chokes the core. What happens then, is that the mass of the star collapses in on itself.
In a binary system, what happens is that as the star ages, it expands massively. Once the star expands past a certain point, it crosses the ‘roche limit’, where the force of gravity from the companion, exceeds that of the expanding star.
Then you have what is called ‘mass transfer’. The mass from the larger star infalls onto the companion. This will continue to the point, where matter stops infalling as the star falls below the roche limit. However, the companion will now have considerably more mass dumped on it and will accelerate it’s evolution.
This is why I believe that it was the former ‘companion’ that became the magnetar. Once the former companion expands, you get the same thing happening, where massloss occurs from the companion back to the original. Except at this point, the star has consumed all of it’s fissionable material in the core, and collapses. This forms a supernova where the remnent left behind is the magentar.
Sure. There are a multitude of things in the Universe that we don't yet understand.
Scientists do their best, and come up with theories. Some of which stand, some do not.
For instance, last week, scientists announced the proton was 4% smaller than science had THEORIZED it was, and that this caused other theories to be reconsidered, and our understanding of physics to (again, like for the 10th time this year) completely change.
Or are you just going to throw crap?
I listed the assumptions I disagreed with and specified why. I am only questioning their theory where they base it on other 'unproven assumptions'. How is that just throwing crap?
Or are we not allowed to 'question' our scientists, in this country?
Well Dark matter being a somewhat unknown entity you could blame it for many “missing holes” in the cosmology theories.
I also think that the idea there could be “Quark Stars” ie, neutron stars that have degenerated due to gravity to break down the quark binding force. So the star becomes essentially a quark soup held together by immense gravity. Now most people in cosmology thing that the “Dark Matter” is weakly interacting massive particles. If the Dark matter would affect the repulsive forces of quarks in quark stars it could be a catalyst to the creation of a singularity.
You know anything about hydrostatic equilibrium?
Yes. It is what forms silver globes that many see as UFO's.
Stars aren’t solid.
Great news for next time I get pulled into the gravity well of a large Star. I can just hit the LightSpeed Button and zip right through the middle of it.
The only thing that keeps them out is the outward pressure of the fusion reactions from the core.
Is the core solid?
Think of a balloon.
I did. Before you mentioned it. However, I couldn't find any facts that would make it a good analogy. For further proof, you never mention it or how it compares to a Star, in any of the rest of your comment.
What happens is that as the star exhausts it’s fuel, the composition changes, from Hydrogen to helium to heavier elements, all the way to iron.
Sounds pretty solid.
Iron actually absorbs energy in nuclear fusion, so it chokes the core. What happens then, is that the mass of the star collapses in on itself.
I thought it burned off it's fuel (mass). Where did all the mass come from?
In a binary system, what happens is that as the star ages, it expands massively.
Wouldn't it's density decrease ? Or does it expand because the helium turns to iron, increasing gravity, which is what makes it get bigger?
Once the star expands past a certain point, it crosses the ‘roche limit’, where the force of gravity from the companion, exceeds that of the expanding star.
No problem with that.
Then you have what is called ‘mass transfer’. The mass from the larger star infalls onto the companion.
Only if the larger star has less gravity (larger size, less gravity), and the smaller star has more density , and more gravity.
This will continue to the point, where matter stops infalling as the star falls below the roche limit.
Isn't that just another way of saying when the energy exchange balances?
However, the companion will now have considerably more mass dumped on it and will accelerate it’s evolution.
There is always a price.
This is why I believe that it was the former ‘companion’ that became the magnetar. Once the former companion expands, you get the same thing happening, where massloss occurs from the companion back to the original. Except at this point, the star has consumed all of it’s fissionable material in the core, and collapses. This forms a supernova where the remnent left behind is the magentar.
Why wouldn't the first star be turned into a supernova ? If the second star absorbed the 'mass' (energy) of the first star, why would it be out of fuel and start to collapse?
BTW, your theory is just as good as the original article's postulation.
It is good to have an open mind and 'think' for yourself. Your theory is just as provable as any that Stephen Hawking proposes (and he has admitted he was wrong before).
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.