http://www.physorg.com/news77984079.html
Type Ia supernovaa are supposed to be a type of cosmic yardtick that have a constant brightness at a given distance. But the article above says they are the result of hydrogen coming off a nearby star that lands on the surface of white dwarf causing a thermonuclear explosion as the white dwarf"s gravity compresses it to thermonuclear densities and tempertaures. The amount of hydrogen from nearby stars might vary a lot and that might make them unreliable, and inconstant light sources.
They were thought to be reliable because the stars can only achieve a certain mass before they explode. However now it is known that (based on the spin of the star) the critical mass is somewhat variable. Also, if two white dwarfs collide it would probably create a much brighter Type Ia (because their combined mass would be greater than the maximum mass of a single star).
This result doesn't invalidate Type Ia supernovae as a yardstick, but it will likely mean that the error involved with using these events as a distance calculator will be increased.
This result doesn't invalidate Type Ia supernovae as a yardstick, but it will likely mean that the error involved with using these events as a distance calculator will be increased.
This BBC Article about the star say the results should not be included as they will contaminate the pool of standard yardsticks. One of the reasons for the exclusion is that no other star of this found at this star's red-shift, which is low.
I'm running on very few pieces of information, but it seems to me these are two interesting observations, 1) low red-shift, 2) surprisingly bright/massive star.
I wonder if there is a link between red-shift and an object's mass or electrical content, and that red-shift isn't solely an effect of the object moving away from us.
I'm running on very few pieces of information, but it seems to me these are two interesting observations, 1) low red-shift, 2) surprisingly bright/massive star.
I wonder if there is a link between red-shift and an object's mass or electrical content, and that red-shift isn't solely an effect of the object moving away from us.
Hi Seanu,
I'm pretty sure general relativity says that a massive object will redshift light coming from it, so there would be that relationship to mass.
Ron
I'm pretty sure general relativity says that a massive object will redshift light coming from it, so there would be that relationship to mass.
Ron
The scientists involved in this study are mistaken. The Chandrasekhar is 1.4 Solar masses its true, but it refers to a limit at which stars CAN go supernova. Any star above this limit of 1.4 solar masses WILL go supernova, that is when its run out of fuel and switches to heavier fuels (i.e. helium) and not because its reached a critical mass. There are countless stars that dwarf our sun and any postdoctorate at UofT should know that.
From what I gather, haveing only read the synopsis' of the study, this isnt anything out of the ordinary.
From what I gather, haveing only read the synopsis' of the study, this isnt anything out of the ordinary.
... umm... the Chandrasekhar limit is the point where election degeneracy is no longer sufficient to hold up the pressure of the star. Therefore, at more than 1.4 solar masses, any object which is not undergoing nuclear fusion (like a white dwarf for instance) will no longer be able to hold itself up against the pressure caused by its gravity. At this point the star will collapse into a neutron star.
If you aren't sure what you are talking about, go and do a google search for crying out loud
EDIT: Spelling
If you aren't sure what you are talking about, go and do a google search for crying out loud
EDIT: Spelling
QUOTE
University of Oklahoma professor David Branch has dubbed this the “Champagne Supernova,” since extreme explosions that offer new insight into the inner workings of supernovae are an obvious cause for celebration.
I just have to say, I reckon he's dubbed it the "Champagne Supernova" because he's an Oasis fan ;-)
Dredawg, I thing you are confusing two types of supernovas.
Generally a supernova occurs when a SUPER GIANT star of mass greater than 8 solar masses is no longer capable to continue fusing the heavier elements within its nucleus hence exploding.
Type Ia supernovas, however, are different. They occur when WHITE DWARFS (IE dead stars which no longer experience nuclear fusion in their core) become too massive due to absorbing mass from other neighboring stars or colliding with another massive enough body (IE they exceed the much smaller value of 1.4 solar masses). Whilst I don’t fully understand the physics behind this, according to Chandrasekhar, once this mass is exceeded the force of gravity of these stares is far greater than the repulsive forces of its nuclear components causing it to obliterate itself (Note the lack of nuclear fusion means that gravity becomes a more significant force at these lower masses). Its mass becomes energy (E=mc^2 comes in here in some form or other) and hence a burst of light is emitted producing a supernova.
PS I am currently still an undergraduate so if anyone feels they can elaborate or improve my explanation please do.
PSS Yes, the Prof definitely looks like an oasis fan, which is a gooooood thing! But does he know a champagne supernova is also champagne +smoking marijuana
.
Hope this answers your question, Dredawg.
Chopo
Generally a supernova occurs when a SUPER GIANT star of mass greater than 8 solar masses is no longer capable to continue fusing the heavier elements within its nucleus hence exploding.
Type Ia supernovas, however, are different. They occur when WHITE DWARFS (IE dead stars which no longer experience nuclear fusion in their core) become too massive due to absorbing mass from other neighboring stars or colliding with another massive enough body (IE they exceed the much smaller value of 1.4 solar masses). Whilst I don’t fully understand the physics behind this, according to Chandrasekhar, once this mass is exceeded the force of gravity of these stares is far greater than the repulsive forces of its nuclear components causing it to obliterate itself (Note the lack of nuclear fusion means that gravity becomes a more significant force at these lower masses). Its mass becomes energy (E=mc^2 comes in here in some form or other) and hence a burst of light is emitted producing a supernova.
PS I am currently still an undergraduate so if anyone feels they can elaborate or improve my explanation please do.
PSS Yes, the Prof definitely looks like an oasis fan, which is a gooooood thing! But does he know a champagne supernova is also champagne +smoking marijuana
.Hope this answers your question, Dredawg.
Chopo
Sorry Chopo, but the eminent scientists who published this research (and the peer reviewed publication that published it) are right.
In short, the limit refers to the maximum size a white dwarf (containing no current fusion). At this point, as those above have said, its integrity fails at a quantum level. The limit is not a limit on supernova production, but a limit on white dwarf size, and is supposed to be an absolute maximum. It cannot go beyond this because it would de facto have gone supernova. The limit has been challenged by some scientists, but only in relation to white dwarfs with a specific chemical composition - and only in instances where the size of the dwarf is slightly under the limit. No one has ever suggested the limit could be increased, until now.
As for its importance as a yardstick, that all depends on how many of these events have taken place, how many have been missed in previous measurements, and whether or not the reason for the limit breach can be determined. Personally I find the spinning object explanation most satisfactory.
Of course, if there have been lots missed, and these events happen frequently, that could mean that the universe is not be accelerating (lots of ifs here but humour me!). If it is not accelerating, there is no need for dark energy. Without dark energy, the universe is a far simpler place, and as a fan of Ockham's Razor, I deep down hope that we will someday will learn that we were wrong - if not through Ia supernova errors, then through some other reason.
In short, the limit refers to the maximum size a white dwarf (containing no current fusion). At this point, as those above have said, its integrity fails at a quantum level. The limit is not a limit on supernova production, but a limit on white dwarf size, and is supposed to be an absolute maximum. It cannot go beyond this because it would de facto have gone supernova. The limit has been challenged by some scientists, but only in relation to white dwarfs with a specific chemical composition - and only in instances where the size of the dwarf is slightly under the limit. No one has ever suggested the limit could be increased, until now.
As for its importance as a yardstick, that all depends on how many of these events have taken place, how many have been missed in previous measurements, and whether or not the reason for the limit breach can be determined. Personally I find the spinning object explanation most satisfactory.
Of course, if there have been lots missed, and these events happen frequently, that could mean that the universe is not be accelerating (lots of ifs here but humour me!). If it is not accelerating, there is no need for dark energy. Without dark energy, the universe is a far simpler place, and as a fan of Ockham's Razor, I deep down hope that we will someday will learn that we were wrong - if not through Ia supernova errors, then through some other reason.
QUOTE (Ralphy+Oct 3 2006, 08:39 PM)
Sorry Chopo, but the eminent scientists who published this research (and the peer reviewed publication that published it) are right.
In short, the limit refers to the maximum size a white dwarf (containing no current fusion). At this point, as those above have said, its integrity fails at a quantum level. The limit is not a limit on supernova production, but a limit on white dwarf size, and is supposed to be an absolute maximum. It cannot go beyond this because it would de facto have gone supernova. The limit has been challenged by some scientists, but only in relation to white dwarfs with a specific chemical composition - and only in instances where the size of the dwarf is slightly under the limit. No one has ever suggested the limit could be increased, until now.
As for its importance as a yardstick, that all depends on how many of these events have taken place, how many have been missed in previous measurements, and whether or not the reason for the limit breach can be determined. Personally I find the spinning object explanation most satisfactory.
Of course, if there have been lots missed, and these events happen frequently, that could mean that the universe is not be accelerating (lots of ifs here but humour me!). If it is not accelerating, there is no need for dark energy. Without dark energy, the universe is a far simpler place, and as a fan of Ockham's Razor, I deep down hope that we will someday will learn that we were wrong - if not through Ia supernova errors, then through some other reason.
Ralphy, you seem to be saying I’m wrong and accusing me of questioning the eminent scientists who published this research (and the peer reviewed publication that published it).
But I never said they were wrong. I was merely trying to simplify the explanation for the non-technically minded. I also was trying to explain to Dredag where i thought he'd gone wrong in misunderstanding the original paper and to point out why the observation carried out by these astronomers was so significant.
I never questioned the authors of the paper. Plus, you then seem to go on to repeat more or less what i said, al be it in a more scientific accurate and thorough way.
Not that it matters any more seeing that I am writing this in early November but you know, no one likes to be told he is wrong, especially when he isn’t!!! lol
In short, the limit refers to the maximum size a white dwarf (containing no current fusion). At this point, as those above have said, its integrity fails at a quantum level. The limit is not a limit on supernova production, but a limit on white dwarf size, and is supposed to be an absolute maximum. It cannot go beyond this because it would de facto have gone supernova. The limit has been challenged by some scientists, but only in relation to white dwarfs with a specific chemical composition - and only in instances where the size of the dwarf is slightly under the limit. No one has ever suggested the limit could be increased, until now.
As for its importance as a yardstick, that all depends on how many of these events have taken place, how many have been missed in previous measurements, and whether or not the reason for the limit breach can be determined. Personally I find the spinning object explanation most satisfactory.
Of course, if there have been lots missed, and these events happen frequently, that could mean that the universe is not be accelerating (lots of ifs here but humour me!). If it is not accelerating, there is no need for dark energy. Without dark energy, the universe is a far simpler place, and as a fan of Ockham's Razor, I deep down hope that we will someday will learn that we were wrong - if not through Ia supernova errors, then through some other reason.
Ralphy, you seem to be saying I’m wrong and accusing me of questioning the eminent scientists who published this research (and the peer reviewed publication that published it).
But I never said they were wrong. I was merely trying to simplify the explanation for the non-technically minded. I also was trying to explain to Dredag where i thought he'd gone wrong in misunderstanding the original paper and to point out why the observation carried out by these astronomers was so significant.
I never questioned the authors of the paper. Plus, you then seem to go on to repeat more or less what i said, al be it in a more scientific accurate and thorough way.
Not that it matters any more seeing that I am writing this in early November but you know, no one likes to be told he is wrong, especially when he isn’t!!! lol
The article suggests that the dwarf star may have been spinning very fast so have been able to accommodate more material before exploding. Another possibility is that the material could build up slowly over time so that the dwarf star was able to accommodate it and not be smothered by it, so allowing dangerous pressures to build up. There is no reason why a star should explode merely because it is "large", 1.5 solar masses or even 50 solar masses.
It is possible that type 1A supernovae explsions rely on an overquick accumulation of mass and that we have not seen dwarf stars explode till much later which acumulate it more slowly. There is an awful lot of trust put in objects which are tiny specks on photo graphic plates, that everyone is exactly the same.
Make that "of exactly the same cause.
It is possible that type 1A supernovae explsions rely on an overquick accumulation of mass and that we have not seen dwarf stars explode till much later which acumulate it more slowly. There is an awful lot of trust put in objects which are tiny specks on photo graphic plates, that everyone is exactly the same.
Make that "of exactly the same cause.
They were the perfect yardsticks, and a certain brightness meant that they were at a certain distance. Except that the mass a dwarf star can hold before it explodes is apparently proportional to it's rate of rotation. Who knows how many were given wrong distances till we finally found one that was impossibly bright so did not fit the pattern?
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