Surface helium detonation spells end for white dwarf

October 4, 2017
The nuclear detonation of the surface helium layer triggered an inward shock wave, and now carbon nuclear fusion has begun at the center. Credit: Institute of Astronomy, University of Tokyo

An international team of researchers has found evidence that the brightest stellar explosions in our Universe could be triggered by helium nuclear detonation near the surface of a white dwarf star. Using Hyper Suprime-Cam mounted on the Subaru Telescope, the team detected a type Ia supernova within a day after the explosion, and explained its behavior through a model calculated using the supercomputer ATERUI. This result was reported in Nature published on Oct. 5.

Some end their lives with a huge called a supernova. The most famous supernovae are the result of a massive star exploding, but a white dwarf, the remnant of an intermediate mass star like our Sun, can also explode. This can occur if the white dwarf is part of a binary star system. The white dwarf accretes material from the companion star, then at some point, it might explode as a type Ia supernova.

Because of the uniform and extremely high brightness (about 5 billion times brighter than the Sun) of type Ia supernovae, they are often used for distance measurements in astronomy. However, astronomers are still puzzled by how these explosions are ignited. Moreover, these explosions only occur about once every 100 years in any given galaxy, making them difficult to catch.

An international team of researchers led by Ji-an Jiang, a graduate student of the University of Tokyo, and including researchers from the University of Tokyo, the Kavli Institute for the Physics and Mathematics of the Universe (IPMU), Kyoto University, and the National Astronomical Observatory of Japan (NAOJ), tried to solve this problem. To maximize the chances of finding a type Ia supernova in the very early stages, the team used Hyper Suprime-Cam mounted on the Subaru Telescope, a combination which can capture an ultra-wide area of the sky at once. Also they developed a system to detect supernovae automatically in the heavy flood of data during the survey, which enabled real-time discoveries and timely follow-up observations.

Surface helium detonation spells end for white dwarf
This image was taken with Hyper Suprime-Cam mounted on the Subaru Telescope. Credit: University of Tokyo / NAOJ

They discovered over 100 supernova candidates in one night with Subaru/Hyper Suprime-Cam, including several supernovae that had only exploded a few days earlier. In particular, they captured a peculiar type Ia supernova within a day of it exploding. Its brightness and color variation over time are different from any previously-discovered type Ia supernova. They hypothesized this object could be the result of a white dwarf with a helium layer on its surface. Igniting the helium layer would lead to a violent chain reaction and cause the entire star to explode. This peculiar behavior can be totally explained with numerical simulations calculated using the supercomputer ATERUI. "This is the first evidence that robustly supports a theoretically predicted stellar explosion mechanism!" said Jiang.

Upper panels show the first two-days observations of a peculiar type Ia supernova, MUSSES1604D, with Subaru/Hyper Suprime-Cam (left and middle) and follow-up observations with the Gemini-North telescope about one month after the first observation (right). Lower panels show the schematic light curves of MUSSES1604D (green circles denote the stages that the supernova is staying during observations). Credit: Institute of Astronomy, the University of Tokyo

This result is a step towards understand the beginning of type Ia supernovae. The team will continue to test their theory against other supernovae, by detecting more and more just after the explosion. The details of their study were published in Nature on October 5.

Explore further: Evidence found of white dwarf remnant after supernova

More information: A hybrid type Ia supernova with an early flash triggered by helium-shell detonation, Nature (2017). DOI: 10.1038/nature23908

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36 comments

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bschott
1 / 5 (5) Oct 04, 2017
This theory is only plausible if you choose to ignore everything we know about helium.
antialias_physorg
5 / 5 (8) Oct 04, 2017
This theory is only plausible if you choose to ignore everything we know about helium.

What exactly is it that 'we' know about helium that isn't in line with thei theory? (And who is this mythical 'we'?)
bschott
1 / 5 (5) Oct 04, 2017
This theory is only plausible if you choose to ignore everything we know about helium.

What exactly is it that 'we' know about helium that isn't in line with thei theory? (And who is this mythical 'we'?)

Well AA, why don't you go learn about helium and then you will have answered this for yourself. It is a novel approach. here, I will get you started:
https://en.wikipe...i/Helium
Read it all, if you still don't understand. Physics is above you.

Whydening Gyre
5 / 5 (3) Oct 04, 2017
This theory is only plausible if you choose to ignore everything we know about helium.

I, too, kinda questioned this as Helium does not present itself as a violently explosive element.
While inert and not-flammable, I would guess there are pressure and temp points beyond which normal observations are no longer relevant. Perhaps a sufficiently rapid change in temp and pressure, interaction with other elements and so on...
Wish they would have explained that a little better....
Da Schneib
5 / 5 (8) Oct 04, 2017
@Whyde, it's a nuclear detonation of the helium, which implies massive prompt helium fusion. But you're right, it's not very well explained in the article. The abstract of the paper (follow the link below the article) explains it a bit better.
antialias_physorg
5 / 5 (9) Oct 05, 2017
Read it all, if you still don't understand. Physics is above you.

Erm..you are aware that the helium flash on white dwarf stars is nuclear fusion? It has nothing to do with chemical reactions.

Stars are mostly (except in the outer layers of the photosphere) too hot for chemical reactions. At the temperatures you find instars atoms are generally ionized.
Whydening Gyre
5 / 5 (4) Oct 05, 2017
@Whyde, it's a nuclear detonation of the helium, which implies massive prompt helium fusion. But you're right, it's not very well explained in the article. The abstract of the paper (follow the link below the article) explains it a bit better.

kinda was where i was going, but just takes me longer to get there...:-)
RealityCheck
1 / 5 (3) Oct 05, 2017
@antialias, @Da Schneib, @Whyde.

From article:
triggered by helium nuclear detonation near the surface of a white dwarf star.
I cannot find where the authors explain how that Helium Fusion 'detonation' can even start for the "near the surface" Helium in that White Dwarf situation. I can only surmise they imply a surface accumulation of Hydrogen ignites FIRST to create the necessary (much greater) heat/pressure compression to ignite underlying "near surface" Helium.

In any case, Perlmutter et al's so-called 'Standard Candle' Supernovae 'data' and assumptions go right out the window, yes?

Anyhow, this highlights what I've LONG been pointing out:

ALLEGED 'standard candle' supernovae can IN REALITY VARY GREATLY depending on local/intervening conditions/contents/dynamics.

So AGAIN the QUESTION is:

How LONG will it be before the 'profession' SELF-CORRECTS; and STOPS churning out scientifically/logically QUESTIONABLE Big-Bang, Accelerating-Universe, Dark-Energy CRAP?
Da Schneib
5 / 5 (3) Oct 05, 2017
@RC, helium fuses to carbon in stars. Get enough helium on the surface of a white dwarf and it goes "boom." This is duh.

https://en.wikipe...um_flash
A much rarer runaway helium fusion process can also occur on the surface of accreting white dwarf stars.

https://en.wikipe..._process

What are you, an idiot? You can't google up "helium fusion?"
Uncle Ira
5 / 5 (6) Oct 05, 2017
@ Really-Skippy. How you are Cher? I am good, can't complain, thanks for asking.

I will try to help you out with that. See it works like this, a helium white dwarf is one where he's already burned up all the hydrogen, but he is too small to start burning the helium, he don't get hot enough. But if he has a neighbor he can start accreting stuffs off of him. Usually is more helium and some hydrogen. All that gets packed together with the degenerate pressure really tight,eh?

Are you following me along so far? Good I knew you could. If the accreting stuffs keeps building up, it starts getting hotter and hotter, once it gets hot enough, the hydrogen and the helium flash all in a sudden.

How you like me now Skippy?
Uncle Ira
5 / 5 (5) Oct 05, 2017
@RC, helium fuses to carbon in stars. Get enough helium on the surface of a white dwarf and it goes "boom." This is duh.

https://en.wikipe...um_flash

What are you, an idiot? You can't google up "helium fusion?"


You beat me to the post him button. Did I get it almost right?
RealityCheck
1 / 5 (3) Oct 05, 2017
@Uncle Ira.
@ Really-Skippy. How you are Cher? I am good, can't complain, thanks for asking.

I will try to help you out with that. See it works like this, a helium white dwarf is one where he's already burned up all the hydrogen, but he is too small to start burning the helium, he don't get hot enough. But if he has a neighbor he can start accreting stuffs off of him. Usually is more helium and some hydrogen. All that gets packed together with the degenerate pressure really tight,eh?
You just effectively confirmed what I already knew/said, mate!...
a surface accumulation of Hydrogen ignites FIRST to create the necessary (much greater) heat/pressure compression to ignite underlying "near surface" Helium.
But thanks anyway, Ira for your erudite confirmation that I knew that already. :)

ps: Ira, maybe you should explain it to Da Schneib-skippy instead of me, hey? :)
RealityCheck
1 / 5 (3) Oct 05, 2017
@Da Schneib.
@RC, helium fuses to carbon in stars. Get enough helium on the surface of a white dwarf and it goes "boom." This is duh.

https://en.wikipe...um_flash

What are you, an idiot? You can't google up "helium fusion?"
Who said that Helium did NOT also fuse in the sun? Not ME, mate!

What I pointed out re that article is, the authors didn't explain that MORE HYDROGEN accreting from a COMPANION would likely be needed to build up sufficient to ignite both that 'surface' Hydrogen layers AND "near surface" Helium layers....like I already said.

ps: DS, even @Uncle Ira, as well as me, already knew that; so why didn't you? And when will your insulting, unheeding ego-tripping kneejerks end, mate? :)
Uncle Ira
5 / 5 (5) Oct 05, 2017
@ Really-Skippy. They don't ALL use hydrogen to make the helium flash. Just most of them. Sometimes the neighbor star does not have hydrogen to give up, sometimes the neighbor only has helium to give up. When that happens, the accreting stuffs is helium and when enough gets piled up, it flashes.
RealityCheck
1 / 5 (3) Oct 05, 2017
@Uncle Ira.
@ Really-Skippy. They don't ALL use hydrogen to make the helium flash. Just most of them. Sometimes the neighbor star does not have hydrogen to give up, sometimes the neighbor only has helium to give up. When that happens, the accreting stuffs is helium and when enough gets piled up, it flashes.
You can't have it both/all ways, mate!

Consider the binary possibilities containing White Dwarf star:

- A White Dwarf and Neutron Star; this would involve the WD losing 'stellar wind' material to the NS; so NO Helium accreting on WD.

- Two White Dwarfs; their 'stellar wind' material exchanges would be roughly equal; so they would be losing/gaining as much as the other; so retaining basically CONSTANT Helium content.

- A White Dwarf with a companion still having Hydrogen atmosphere; much of that companion's 'stellar wind' would be Hydrogen; so its accumulation on White Dwarf would ignite that Hydrogen FIRST.

Choose your preferred binary context, Ira. :)
Uncle Ira
5 / 5 (5) Oct 05, 2017
You forgot one on your list Cher. (I am thinking you did that on purpose).

You left off: A white dwarf who's companion is no longer having any hydrogen left, it might be a helium star with enough helium to fusion the helium. If all he has left is helium, that is what is going to be accreted.

Tell me you left that off hoping to try to double talk me with lawyer tactics, eh Cher? Because if that is not what you were doing, you are even more the ignorant than I was 25 years ago..
RealityCheck
1 / 5 (3) Oct 05, 2017
@Uncle Ira.
A white dwarf who's companion is no longer having any hydrogen left, it might be a helium star with enough helium to fusion the helium. If all he has left is helium, that is what is going to be accreted.

Tell me you left that off hoping to try to double talk me with lawyer tactics, eh Cher? Because if that is not what you were doing, you are even more the ignorant than I was 25 years ago..
I left out that binary combination as unlikely in the article's context; for such a Helium-Only star to burn helium it would have to be supermassive/superhot (which it may be INTERNALLY DEEP DOWN around its core). HOWEVER, for its Helium to 'burn' in the OUTER ENVELOPE of such a HELIUM-ONLY STELLAR companion, it would require a FLASH EVENT of its OWN....which would have EITHER destroyed/expelled the WD from their binary AND/OR made that HELIUM-ONLY-star companion ITSELF go Supernova!

Either way, a heat/pressure 'trigger' needed to ignite 'near surface' Helium. :)
Da Schneib
5 / 5 (4) Oct 05, 2017
You beat me to the post him button. Did I get it almost right?
Pretty close, @Ira. Helium stars and helium flash are different phenomena, but the part about collecting helium on the surface until there's enough of it to go boom is correct. There is some speculation about helium stars generating carbon, but nobody knows how it might get out. A Type Ia supernova might do 'er.
Da Schneib
5 / 5 (3) Oct 05, 2017
The problem with you, @RC, is whenever you get pwnt you try to pretend that's what you were saying all along.

Here's a quote:
I cannot find where the authors explain how that Helium Fusion 'detonation' can even start for the "near the surface" Helium in that White Dwarf situation.
You're lying again, @RC. This thread added to the list of your lies.

Shall I post all your lies again, @RC? Go ahead, post here again and I will.
RealityCheck
1 / 5 (3) Oct 05, 2017
@Da Schneib.
The problem with you, @RC, is....
PAY ATTENTION will ya? It's SUBTLE. Not simplistic, like your 'wiki-regurgitated' already-know stuff which DOES NOT ADDRESS/ANSWER the ACTUAL point I made in CONTEXT of ABOVE ARTICLE's SPECULATED 'explanation' for 'unusual' SN.

Consider:

IF the 'near surface' Helium could be ignited to fuse as they suggest, THEN ALL White Dwarfs which had accumulated the necessary HYDROGEN to ignite the 'usual' way would ALSO have ignited their "near surface" HELIUM layers....which would have DESTROYED ALL WDs LONG BEFORE the HELIUM ONLY accretion stage was ever reached.

You can't have it both/all ways!

Hence WHY I pointed out the lack of actual CONSISTENT explanation for why THAT WD had exploded NOW due to "near surface" Helium igniting, YET did not explode during its Hydrogen accretion/nova stage.

ps: @DS, please stop regurgitating/kneejerking/confusing issues, and start paying attention to the ACTUAL (if subtle) points raised. :)
Da Schneib
5 / 5 (4) Oct 05, 2017
Fine, bend over, here it comes.

Thread where @RC lies about current research into cosmic voids and gets caught: https://phys.org/...ies.html
Thread where @RC makes conflicting claims within ten posts and gets caught: https://phys.org/...ome.html
Thread where @RC claims there is "REAL/PHYSICAL UNIVERSAL 'infinity'" and gets caught: https://phys.org/...rgy.html
Thread where @RC claims Rubin said galaxies will implode with out DM and confuses Zwicky with Rubin:
https://phys.org/...zzy.html
Thread where @RC claims his "non math" approach is both abstract and non-abstract, and both is and is not math: https://phys.org/...ure.html
Da Schneib
5 / 5 (4) Oct 05, 2017
Thread where @RC lies about how long it takes a shockwave to move through a giant molecular cloud: https://phys.org/...cal.html
Thread where @RC lies fifteen times in ten posts and still can't stop, even when told he's being baited into lying: https://phys.org/...h_1.html
Thread where @RC lies that defining a black hole is "calling it black." https://phys.org/...ole.html
Thread where @RC lies about helium flash white dwarf detonations: https://phys.org/...arf.html

This troll lies, just about every time it posts. There is no reason why anyone at all should ever pay any attention to what it says. Just tell it it's lying again, and move on. Eventually it might beg, borrow, or steal a clue. After that it will need written instructions for dealing with its New Clue. These can be provided on request.
Da Schneib
5 / 5 (3) Oct 05, 2017
You keep tellin' 'em, @RC, and I'll keep addin' 'em to the list and publishing it every time you lie some more. I'm enjoying this and I know you won't stop. You've already proven that. You're too stupid and too arrogant to stop.
RealityCheck
1 / 5 (3) Oct 05, 2017
@Da Schneib.

The @Forum will note that you EITHER did not read and/or did not understand the subtle point explained to you in my previous post, OR that you cannot understand/address that subtle point raised/explained for your honest response (and NOT just more of your lame spammed 'pre-prepared' lies and evasion tactics in lieu of honest discourse engagement with the science/logics issues raised).

DS, you have again failed the test for all would be scientists; you have betrayed the objectivity and fairness principles underpinning the Scientific Method/discourse ethics/aims. Bad, mate; really bad. You have disappointed at every opportunity I have given to you so far. Are you drunk so often that you cannot change your ways, mate? If so, then you have become just another drunk poster on the net. Too bad. What a waste.
Da Schneib
5 / 5 (3) Oct 05, 2017
I can't even imagine what you might say, @RC, after being proven a liar, that anyone might care about. It can only be more insults, lies, and misrepresentations, since that's all you ever say here.

Go away, troll.
RealityCheck
1 / 5 (3) Oct 05, 2017
@Da Schneib.
I can't even imagine what you might say, @RC, after being proven a liar, that anyone might care about. It can only be more insults, lies, and misrepresentations, since that's all you ever say here.

Go away, troll.
Why need you "imagine" anything, DS; it's all there in black and white; in my last two posts especially. If you bothered to actually pay attention you might have seen that the point I raised (and which you have ignored in favor of your unheeding kneejerking/spamming/evasion tactics) needs clarification by the authors before their claims make any logical sense, let alone physics sense, based on known science. That you prefer to insult and spam instead of actually paying attention, and maybe learning something instead of regurgitating stuff I already knew long before you, says all the things about you that the @Forum needs to know when reading your spam tactics, DS. Too bad.
Da Schneib
5 / 5 (3) Oct 05, 2017
Now back to our regularly scheduled thread since we've disposed of the troll @RC:

This paper from 2010 seems significant, as it predicted a helium flash could result in a white dwarf supernova by compressing the core enough to pass the Chandrasekhar limit even though it doesn't have enough mass: https://arxiv.org...002.2173

It seems to me that the phenomena discussed in that paper are exactly what the paper underlying this article are saying they detected, a helium flash followed by a Type Ia supernova.

Discuss.
RealityCheck
1 / 5 (2) Oct 06, 2017
@Da Schneib.
Now back to our regularly scheduled thread since we've disposed of the troll @RC
Why do you keep doing this, DS? It's obvious to all readers that MY POST was polite, on topic, and raised serious valid science/logics points; while YOU, DS, have been TROLLING, insulting and ignoring my clarification of my main point (see below) needing to be addressed by you/the authors.
This paper from 2010 seems significant, as it predicted a helium flash could result in a white dwarf supernova by compressing the core enough to pass the Chandrasekhar limit even though it doesn't have enough mass: https://arxiv.org...002.2173
Can you now adress my point: IF 'near surface Helium' could be so readily 'ignited' to fuse, then EVERY White Dwarf that forms and has its FIRST accreted-HYDROGEN-layer ignition-FLASH should have DESTROYED the WD before any Helium-only accretion stage ever reached!
Discuss.
That's what I've been POLITELY trying to get YOU to do, DS. :)
bschott
not rated yet Oct 11, 2017
Hey Mainstream guys, hot Helium fusion. Show me one example of where we made it happen. IOW, more mathematical theory based on thermal pressure and density calculations with no analogue in reality because it cannot be tested. You guys have no idea how ridiculous it looks when you peacock strut out an answer that you think is rock solid despite the fact that what you are saying is purely theoretical and nothing close to it has ever been achieved in experimentation. Why not just say God did it and throw an equation out that shows it is no longer theory?
434a
not rated yet Oct 11, 2017
Hey Mainstream guys, hot Helium fusion. Show me one example of where we made it happen. IOW, more mathematical theory based on thermal pressure and density calculations with no analogue in reality because it cannot be tested. You guys have no idea how ridiculous it looks when you peacock strut out an answer that you think is rock solid despite the fact that what you are saying is purely theoretical and nothing close to it has ever been achieved in experimentation. Why not just say God did it and throw an equation out that shows it is no longer theory?


Are you saying there's no such thing as helium fusion in nature?
bschott
not rated yet Oct 11, 2017

Are you saying there's no such thing as helium fusion in nature?

No, I am saying that because there is an equation that can be derived using gravitational compression overcoming thermal pressure to fuse helium on the surface of a body in space, doesn't mean that it can or does happen.
434a
not rated yet Oct 11, 2017

Are you saying there's no such thing as helium fusion in nature?

No, I am saying that because there is an equation that can be derived using gravitational compression overcoming thermal pressure on the surface of a body in space, doesn't mean that it can or does happen.


Ok, so you have an alternative explanation for the observations made with the telescope that fits better than the one that team came up with?
bschott
not rated yet Oct 11, 2017
Ok, so you have an alternative explanation for the observations made with the telescope that fits better than the one that team came up with?

There is no observation made with a telescope of any Stellar body accreting mass from a binary companion...not a single one. So if you are asking me for an alternate explanation to what could generate a bright flash of light that slowly fades (BTW, "explosions" do not "fade out") there are many examples of phenomenon which do this. As they involve plasma , all are more likely than a helium fusion explosion.
434a
not rated yet Oct 12, 2017
http://iopscience...ulltext/

Doppler tomography of Halpha; spectra of four Algol-type binaries TT Hya, SW Cyg, U CrB, and U Sge has revealed quasi-stable accretion disks around the mass gaining star in each system. In the tomograms, these accretion structures are nearly symmetric distributions of gas between the stellar surface and the Roche lobe around the mass gainer. The disk is most stable in TT Hya and SW Cyg, which have orbital periods greater than 4.5 days. However, the morphology of the accretion structures in the shorter period systems, U CrB and U Sge, can change from a disklike distribution to a streamlike distribution. During a streamlike epoch of these systems, the gas stream in the Doppler tomogram closely follows the predicted free fall path from the inner Lagrangian point toward the mass gainer. However, during the disklike stage, the intensity of the disk is comparable to that of the gas stream. Cont
434a
not rated yet Oct 12, 2017
These tomograms display the first maps of accretion disks in the Algol-type class of interacting binaries.
The Halpha; spectra were obtained with the stellar spectrograph at the Kitt Peak National Observatory 0.9 m Coudé Feed Telescope and the National Solar Observatory McMath-Pierce Telescope from 1993 March to 1994 December.

I don't know about you but when I read that paper it said data collected from a telescope mapped the infall of gas to the accretion disk from one star to another in a binary system.

Again I would ask - as you did throw the stone so to speak - do you have a better explanation for the observations made in the article. "They all involve Plasma" is a bit hand wavey if you don't mind me saying so. "No" is a perfectly acceptable answer by the way.
bschott
not rated yet Oct 12, 2017
Doppler Tomography of Halpha doesn't image helium for starters, is interpretive as opposed to a direct imaging technique (Hence why I said no observation has been made) and to come to a conclusion using it the results are fed into a model that has pre-existing parameters as opposed to measured ones. None of the candidates where it is used to claim to view an accretion disk around a white dwarf have yielded a nova as of yet.
"They all involve plasma" means that our observations of nova behavior match the evolution of a plasma discharge, not a thermonuclear blast.
when I read that paper it said data collected from a telescope mapped the infall of gas to the accretion disk from one star to another in a binary system

You have read someone elses interpretation of Halpha tomography perfectly. But it cannot even be used to support Helium accretion...or Helium fusion as suggested above.

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