November 16th, 2011, 11:49 AM
Type 1a supernova happen when gas from a red giant falls onto a white dwarf. Ok?
I would assume the red giant star was very close to the explosion, therefore, got one hell of a shock when its little friend exploded.
But I can't see any references to the remains of the red giant in supernova remnants.
Surface gravity on a red gaint is tiny, I would expect to see a big trail of gas bigger in mass than anything thrown off the white dwarf.
Or have I got my physics twisted?
Nope, not OK.Originally Posted by PetTastic
They might happen that way. They might happen when enough random dust falls on a white dwarf.
And they might happen in some other way.
So far, nobody can produce a model of a white dwarf exploding that fits the data well enough that we can be sure. This is one of the great next steps in astrophysics. Maybe.
Yeah. Funny, that.I would assume the red giant star was very close to the explosion, therefore, got one hell of a shock when its little friend exploded.
But I can't see any references to the remains of the red giant in supernova remnants.
Are you suggesting that scenario is the most popular, because a slow gentle process that goes bang at a fixed threshold is an ideal standard candle?
Also, lots of type 1a remnants look spherical, but I would have thought that the slow accretion process would spin the white dwarf up causing an explosion starting from the poles.
The star Tycho G is thought to perhaps be the companion to the star that gave rise to the SN 1572 supernova.
More info:
Tycho G
SN 1572
Tycho’s Supernova Went Boom After Slurping Up Some of Its Neighbor
November 17th, 2011, 05:12 AM
Very odd!
Tycho G is a type G2 star like our sun!
How can you you go through all of this:
(wikipedia)
And end up with a star like the sun
The star needn't have been a red giant before its partner went boom.I only mentioned Tycho G as a possible jumping off point for further research on your behalf. Clearly the evidence is not iron clad, but it appears to be the best available. To me the take home message would appear to be that the companion star is generally not thought to be destroyed; instead, it is shot off on a speedy trajectory.
I found quite a few articles and discussions on the released papers.
Firstly, issues on its luminosity vs temperature, is it a giant or low density star in the nebula or a standard type G2 star line-of-sight object?
Could not find any claims for extra absortion lines cause by nebula mattieral.
Second problem is its age, if it was in a close binary with the star that turned white dwarf, it would be the same age.
The other star could not have been big enough to age rapidly if turned into a white dwarf instead of exploding.
How did it avoid being gold plated in the supernova? (suggestions that the shock wave cause a burst of fussion resulting in tycho G puffing off a dirty outer shell after the nova event)
Large yellow white stars have strong solar winds making transfer of gas to a companion probably very inefficent, most of the gas would get blown away. Meaning Tycho G would have needed to be a giant, but aging slowly, loosing many solar masses.
There is also an interesting claim in one of the papers that if you blow the outer layers of a G type star the result is still G type. ( Is possible, but never heard of anybody modeling it.)
I agree that Type 1a's are poorly understood. I'm no astronomer, but it's my understanding that main sequence stars are quite capable of dumping mass onto a white dwarf companion. Indeed, solar winds are one proposed mechanism by which the white dwarf can gain mass.
The impact of type Ia supernovae on main sequence binary companions
Interesting paper. High performance computer game particle systems is one of my specialities. I have played around trying to model galaxies and dark matter with them.
Possibly, I would question that hydrogen fusion caused by the shockwave can be ignored, particularly in the area directly between the 2 stars.
Maybe also they could have tried the effects of a thinner denser shell of material hitting it.
Anyway for now I think we just need to assume Type 1a's can be used as good standard candles, even if we don't understand exactly what they are.
Apologies for digging up an older post, but I figured this was relevant.
A recent Type 1a supernova has been observed in M101 (The Pinwheel Galaxy), 21 million light years distant. The companion is thought to have been a main sequence star (due to an absence of evidence for a red giant companion). Possibly a nice confirmation of the white dwarf hypothesis too. Also, might be interesting to see if they can find and track the companion star.
Story on Nature News: Early observations identify star at heart of nearby supernova
I had a quick go at trying to model an alternative that seems to work quite well.
The idea is that the white dwarf was formed from a red giant that threw off shells of material, but a dense interstellar medium stopped the shells from clearing the star's gravity.
It later fell back to cause the explosion.
The main question is how much the density of the ISM effects the radius of the heliopause.
In guesstimates based just based on pressure, I could easily get is as close as 10 AU for observed densities of ISM in interstellar clouds, for a star with weak solar winds.
If the shell of expelled dust reacted with the hydrogen in the ISM, and condensed into steaming lumps of icy mud it might be very hard to detect.
Hi PetTastic,
I pulled up your "us shrinking" thread. I saw it from the same source as Summerwind found it.
As to a red giant's blow-off in supernova explosions, it seems like somewhat of a problem in astronomy. Although some papers have claimed to have seen such indications of "blow off" from a companion binary, there are many more that do not claim any such observations. Also there is conflicting evidence/ hypothesis that type 1a supernova may be instead based upon a collision of white dwarf binaries spiraling into a collision or other explanation since companion stars, because of distances, are not discovered except for possibly neighboring galaxies. Since their luminosity vs. redshift is very consistent, it would seem logical that there is probably only one primary cause. If the luminosity does not match the luminosity then it could be classified as type 1b, or c etc. supernova, or if brighter, a type 2 supernova, an exploding super-giant.
Supernovae
Type Ib and Ic supernovae - Wikipedia, the free encyclopedia
Last edited by forrest noble; December 20th, 2011 at 12:38 AM.
I just thought it was interesting that the trapped shells idea, only required less than a kg per cubic km of suborbital material to be trapped 25 to 100 AU out, in order to take the white dwarf over the limit when it returned.
This is linked to the Us/Atoms Shrinking stuff, and the Condensing Universe model, by the way, it forces you to model galaxies as rapidly growing, or dying. (never just rotating)
You get the observed rotation velocity curve, just with a 7 to 12 degree difference in the direction of travel.
The problem is the model predicts large numbers of stars dying at the edges of older galaxies, but this is not observed.
I was looking for a link between the density of the ISM and supernova rate or brightness to explain it.
Thin or no ISM at the edges or in dark galaxies then no trapped shells.
I was also looking at the idea that a supernova outside the ISM is almost invisible at a distance, because all the ejected material just flies of at a 1/6 of the speed of light.
As it expands thermal collisions stop after only 3 hours, after that it just cold matter traveling at relativistic speed.
All gamma rays released by radio active decay, just escape without causing heating after only 4 hours. (approx)
The average collision time for out going heavy elements with protons in the intergalactic medium could be 5 to 50 years.
Just looking at it, as an interesting hobby, when I should be working on my book.
Last edited by PetTastic; December 20th, 2011 at 11:47 AM. Reason: Numbers wrong
PetTastic,
There are many ways type 1a supernova can be modeled as to the details of it. I do not have any particular insight into it and a trapped shell system sounds good to meI just thought it was interesting that the trapped shells idea, only required less than a kg per cubic km of suborbital material to be trapped 25 to 100 AU out, in order to take the white dwarf over the limit when it returned.but such mechanics do not relate to my cosmological model, which as you may know is a diminution of matter model that has kinship with your own ideas.
My own model of the universe is of a much older universe but still finite in time, using a different theory of gravity including different gravity equations (no dark matter). It does not have any particular time limit for galaxies to grow or age; both accordingly take much longer than the present model. There seems to be nothing more needed for this model at the present time, to generally explain observed galaxy or cluster rotation curves.This is linked to the Us/Atoms Shrinking stuff, and the Condensing Universe model, by the way, it forces you to model galaxies as rapidly growing, or dying. (never just rotating). You get the observed rotation velocity curve, just with a 7 to 12 degree difference in the direction of travel.
My model similarly predicts large numbers of dying stars at the edges of the galaxies. In my own model red giants are not considered dying stars. Only when they nova and become a white dwarf are they accordingly described as "dying" in this model. At the edges of our galaxy or others of our age, we could not see large quantities of white dwarfs, brown dwarfs, or black dwarfs (which exist in the model since accordingly the universe is much older). But none of these types of "dark matter" are needed to explain galaxy rotation rates in my own gravitational rotation model.The problem is the model predicts large numbers of stars dying at the edges of older galaxies, but this is not observed. I was looking for a link between the density of the ISM and supernova rate or brightness to explain it. Thin or no ISM at the edges or in dark galaxies then no trapped shells.
I expect there would seemingly be very few supernovas exploding outside of galaxies. It would require a very large star to be ejected from a galaxy, whereas usually the largest stars instead do the ejecting of smaller companions or eject stars by chance encounters. Seldom would there seemingly be a large enough star and circumstances enabling the ejection of a blue super giant.I was also looking at the idea that a supernova outside the ISM is almost invisible at a distance, because all the ejected material just flies of at a 1/6 of the speed of light. As it expands thermal collisions stop after only 3 hours, after that it just cold matter traveling at relativistic speed. All gamma rays released by radio active decay, just escape without causing heating after only 4 hours. (approx) The average collision time for out going heavy elements with protons in the intergalactic medium could be 5 to 50 years.
I do the same thing as you but look at it as more than a hobby, but still we/ all must allow adequate time for other things. My own book concerning cosmology and theoretical physics, has never been published but copyrighted a number of times. I look at it as a living document on-line that on a regular basis requires improved amplification of the details. Even though there have been no major changes in the course of its existence there have been, what I consider to be, very important addendums to itJust looking at it, as an interesting hobby, when I should be working on my book.
I have a German publisher right now for this book that will publish a hard cover version of it now for about 60 Euros, but I wish to publish a soft cover version for no more than 10-15 Euros, for wider distribution. Afterwords I could publish a hard cover version if the demand was there. If I gave my publishing rights up to the German publisher now in exchange for their publishing it, I would have no control over the price, nor the marketing (which I expect at the present time would be little), unless I do the marketing myself . So I am waiting to do it my way, maybe next year. I will write another book for the German publisher which I hope to be able to give them by the end of next year. By about 2020 I expect such ideas/ books in cosmology will be in higher demand after the James Webb goes up and they realize that the BB model is wrong after continuous observations of old appearing galaxies at the farthest reaches of the universe.
Keep up the good work and ideas, Forrest
Last edited by forrest noble; December 20th, 2011 at 06:43 PM.
Looks like in this case they have found no evidence for a large companion star yet.
400-Year-Old Star Explosion Mystery Finally Solved | Supernovas & White Dwarf Stars | Star Mysteries & 219th American Astronomical Society Meeting | Space.com
Not sure I like the two white dwarfs colliding idea any better than accreting material from a larger companion, but this looks like good evidence.
What percentage of stars are white dwarfs?
For several years now I've been aware of this alternative hypothesis for type 1a supernova, which related to two white dwarfs colliding. This article is either proof or strong evidence concerning two white dwarf stars colliding. The presumption, I believe, is that the two stars were very close binary stars. I kinda favored the red-giant accreting model but it is what it is. Although it has been widely discussed that there could be more than one mechanism, at least the exploding star accordingly should be a white dwarf for the explosion to display such a uniform consistency.Not sure I like the two white dwarfs colliding idea any better than accreting material from a larger companion, but this looks like good evidence.
It depends upon what cosmological model you follow. In the standard model estimates say that around 6-7% of the stars are white dwarfs. Still, it is presently believed that around 97% of the stars are bound to end up as white dwarfs in the future (due to their present mass).What percentage of stars are white dwarfs?
What percentage of stars are white dwarfs
In matter shrinking models there might be maybe twice this amount of white dwarf stars, many more red dwarfs, and also some black dwarf stars, which would be based upon a much older universe.
Because of their dimness we can only observe the closer individual white and red dwarf stars in our galaxy.
Last edited by forrest noble; January 12th, 2012 at 06:18 PM.
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