White dwarfs' tidal effects may create novae, study says

Sep 21, 2012 by Susan Kelley
White dwarfs' tidal effects may create novae, study says
The white dwarfs J0651A and J0651B have the shortest orbital period of any known pair of stars that are completely detached from each other. They orbit each other every 12.75 minutes. Credit: Jim Fuller

(Phys.org)—Theoretical physicists at Cornell may have found a new way to explain the formation of novae, stars that suddenly become very bright then quickly fade.

At the heart of the theory is a pair of old, dense stars called white dwarfs, orbiting each other so closely that their create violent tidal waves of plasma that break near the surfaces of the stars. The phenomenon is what the researchers have dubbed a tidally induced nova.

If their theory is correct, it would represent a big step forward for , said lead researcher Jim Fuller, a Ph.D. candidate in the field of astronomy and space sciences. "It's an important problem because there are a lot of white dwarfs in tight binaries," said Fuller, who co-wrote the study with Dong Lai, professor of astronomy. "They're spiraling in toward each other, so tidal effects are going to be very important, but no one has really studied that."

The types of white dwarfs Fuller and Lai have been researching orbit each other very quickly, in less than half an hour. Because white dwarfs are so dense, their gravitational forces are strong enough to pull the stars toward each other in an increasingly tighter spiral. The forces deform the stars, squishing each sphere into an oval, as well as synchronizing them so they spin at the same rate as they orbit and causing enormous gaseous tidal waves. The friction caused by the tidal forces also generates enormous heat, potentially more heat than the sun emits.

Fuller and Lai theorize that the heat is deposited at the of that coats a white dwarf. Hydrogen makes up only 0.01 percent of a white dwarf's mass. But hydrogen is volatile, and heat generated from the tidal friction is enough to spark a . That heat in turn sparks further reactions, triggering in effect a series of exploding atomic bombs. "Those reactions accelerate until all the hydrogen burns off very quickly, and that's a tidally induced nova," Fuller said.

The nova eventually flames out, and the white dwarfs continue to and spiral in toward each other over time.

It may take awhile to prove the theory is correct. White dwarfs are notoriously dim and hard to see. Tidally induced novae probably occur just once every few decades and are likely to last only a few days. "So we'd have to be looking at the right place at the right time. You'd have to get lucky to see one," Fuller said. But specific clues at the site of a burnt-out nova would bear the theory out: two white dwarfs circling each other in a short period of time with little or no hydrogen on their surfaces, along with no X-ray emissions nearby. (X-rays are usually present before and after a nova forms in the normal way—when a white dwarf strips gases off a nearby star and the gases ignite.) "The absence of X-rays would indicate the nova had been tidally induced," Fuller said.

The paper, "Tidal Novae in Compact Binary ," appears in Astrophysical Journal Letters (756:1). The research was supported in part by the National Science Foundation and NASA.

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cantdrive85
1 / 5 (12) Sep 21, 2012
"At the heart of the theory is a pair of old, dense stars called white dwarfs, orbiting each other so closely that their gravitational forces create violent tidal waves of plasma that break near the surfaces of the stars. The phenomenon is what the researchers have dubbed a tidally induced nova."

Tidal waves of plasma? Wow, theoretical physicists pseudo-scientific sci-fi hypotheses (not theories) strikes again. Plasma is directed by EM forces, the effects of gravity on plasma is negligible at best, not matter the claimed system.
rkolter
5 / 5 (11) Sep 21, 2012
Why wouldn't plasma, which is baryonic matter after all, not be affected by gravity? I am pretty sure that you are wrong about this. The fact that plasma is electromagnetic does not mean it is immune to gravity.

Jitterbewegung
3.4 / 5 (10) Sep 21, 2012
The gravity is pretty strong on a white dwarf. Plasma is just a hot state of matter.
cantdrive85
1 / 5 (9) Sep 21, 2012
EM forces are 39 orders of force stronger than gravity, it's kinda like the difference between being simultaneously punched by a fly while being run over by a locomotive. Sure the fly has some effect, but clearly it's the locomotive that does the most damage. Regardless of their claims of fantastic gravity compression or what ever their claim is, EM remains 39 orders of force stronger.

Jitter, there is quite a bit more to it than being hot, it carries an electrical charge which greatly alters the physics that need to be used to describe it properties.
sigfpe
5 / 5 (5) Sep 21, 2012
rkolter,

From the point of view of the white dwarf the plasma looks electrically neutral because the separation between the positive and negative charges is many orders of magnitude smaller than the separation between the plasma and the white dwarf. So the gravitational tidal forces will dominate over electrical forces
RealityCheck
1.3 / 5 (7) Sep 21, 2012
Hi everyone.
From my own researches/understandings of relevant phenomena, I am bound to say that cantdrive85 may be partially correct. If we consider the whole electro-magnetic phenomena set involved in the system of closely orbiting white dwarfs, then their magnetic fields must be interacting/contorting each other to the point that intense twists and knots will trap plasma within them much as solar sunspot loop phenomena traps plasma. The flares one sees in our sun is when these loops/arcs break and the fieldlines 'reconnect' by pinching off the plasma/energy contained in the 'trap' now 'sprung'. Similarly, there must be tremendous energy traps building and breaking between the dwarfs' interacting magnetic fieldlines/pattern. So the 'novae' may be happening in the space ABOVE/BETWEEN the White Dwarfs' surfaces, not ON them? Speculation? Maybe; maybe not. Cheers!
cantdrive85
1 / 5 (8) Sep 21, 2012
rkolter,

From the point of view of the white dwarf the plasma looks electrically neutral because the separation between the positive and negative charges is many orders of magnitude smaller than the separation between the plasma and the white dwarf. So the gravitational tidal forces will dominate over electrical forces


If a white dwarf exists in the manner that they describe (and that's a definite if), or if it's something else all together, it is plasma, and as such will have an electrical charge, it must or it's not plasma, and to be at the temperatures they claim, it absolutely must be plasma. That being said, EM forces will dominate and that is a well understood (not by astrophysicists) fact!
cantdrive85
1 / 5 (6) Sep 21, 2012
The process that astrophysicists claim to be "magnetic reconnection" is correct, but it's not reconnection at all, it's the process Hannes Alfven discovered 75 years ago, an exploding double layer.
RealityCheck
2 / 5 (8) Sep 21, 2012
General Reminder for the benefit of informed discussion re plasma:

Plasmas are assumed to be created/exist as an overall ELECTRICALLY NEUTRAL fluid containing practically equal numbers of electrons and the ions they came from (much as a copper wire is electrically neutral overall). Only where there is a 'separator' mechanism to bring positive ions and negative electrons to different locations in a body of plasma will there be any electrically charged regions. In that maelstrom of twisting and knotting magnetic fieldlines and plasma flowlines, the instability would be too great a 'mixing' factor for such regions to develop let alone stably persist for any significant duration/extent.

So the plasma acts like the neutrally charged plasma in a fusion reactor which has its own instabilities 'damped' by man-made/designed magnetic containment/correction systems not present in the scenario of White Dwarf interactions I described earlier.

Cheers!
cantdrive85
1 / 5 (6) Sep 21, 2012
Reality, I don't think your definition of plasma is correct, this is how plasma physicist Anthony Peratt describes plasma:

Plasmas are conductive assemblies of charged particles, neutrals and fields that exhibit collective effects. Further, plasmas carry electrical currents and generate magnetic fields. Plasmas are the most common form of matter, comprising more than 99% of the visible universe.

http://plasmauniv...tml#what

Not trying to nit pick, but there are some misconceptions about plasma, especially plasmas in space.
PinkElephant
5 / 5 (2) Sep 22, 2012
@cantdrive85,

You're underestimating the strength of gravity at the surface of a white dwarf. White dwarfs are extremely dense, consisting of degenerate matter, just one step removed from becoming a neutron star. The gravitational acceleration at the surface of a white dwarf is something like 100,000 times what it is on Earth (so, if you could stand on that surface, you'd weigh something like 10,000 tons -- in other words you won't be standing; you'd be smeared in a thin film around that surface.)
vega12
5 / 5 (5) Sep 22, 2012
He's not underestimating anything. He's seemingly purposefully misconstruing for the sake of inciting argument and to derail any meaningful discussion.
_traw_at
not rated yet Sep 22, 2012
Having ~just~ studied these dwarf pairs in the past few weeks,I'm fairly confident these scientists have pointed to a plausible cause for the novae.
The tidal action(s) could pull the surface, or even just part of the surface, of one of the dwarfs past the Chandrasekhar Limit an action which would, partly due of the presence of the magnetic fields and the plasma, trigger the detonation.
More thought will be put into this new proposal, and researchers will find more signals to watch for. There is a small chance some of the evidence of proof may already be in the data they already have.

RealityCheck
1 / 5 (5) Sep 22, 2012
Hi cantdrive85. My description (not definition) was in context of article's White Dwarf environment/processes I mentioned as possible explanations of the 'novae events'. Remember, just as copper wire 'overall neutrally' made up of roughly equal & - charges/ions, so is the 'overall neutral' plasma state normally found in nature ( unless some mechanism 'separates' those /- charges). When that happens, it's no longer a plasma, but a mass/motion of like charges. Any 'current' in a neutral wire/plasma represents the mobility of -/ charges towards either end of a CIRCUIT. At no stage is the wire/plasma itself 'overall' charged. But any segregated collection/flow of LIKE charges is merely a mass/stream of either electrons(positrons) and ions(protons) etc. BUT while a neutral wire/plasma supports CURRENTS of one charge or the other in different directions, the 'like charge plasma' which you mention does NOT actually CONDUCT a CURRENT of charges, they ARE the CURRENT/MOVEMENT of charges! :)
vega12
5 / 5 (1) Sep 23, 2012
http://en.wikiped...n_matter
The distinction between current and moving charges is non-existent. Current is defined based on charge fluxes. Your other point about the overall neutrality of plasma is correct though. It is precisely because the EM force is so powerful and that it works on opposites that the universe on a large scale is neutral. This allows the only additive gravitational force to be dominant. That is not to say there are no E M effects. Obviously you still have charge particles flowing around magnetic field lines of all manner of celestial bodies. But saying "only gravity is important" or "only EM is important" are both not exactly correct. Nature is more subtle and difficult than we might want it to be. None of the forces are entirely negligible on the cosmic scale, as as we all know nuclear forces are extremely important for stars as well as EM and gravity.
LED Guy
5 / 5 (4) Sep 24, 2012
@cantdrive85

Damn, you're right! The entire sun is made of plasma, it can't possibly be held together by mere gravity. It should have exploded long ago. The same goes for the galaxy and galaxy clusters.

Wait a minute, the electrons in the atoms that make up you body are subject to the same forces of gravity, how can they be bound?

What a troll. You can't even realize that although the gases in a plasma are charged, the net collective of the plasma is essentially neutral. EM forces are nothing compared to the strong and weak nuclear forces. Get a grip on reality and put things in context.
RealityCheck
1 / 5 (4) Sep 25, 2012
HI vega12.
The distinction between current and moving charges is non-existent. Current is defined based on charge fluxes. Your other point about the overall neutrality of plasma is correct though. ...
If you read my post again, I made no distinction between moving charges and current. I made a general point/analogy of 'neutral' plasma flowlines being like a 'copper wire' (both -/ charges make it up) which can 'conduct' a 'current' of charges along it, just like a wire does. I then made the further point to cantdrive85 that any 'charged plasma' IN MOTION would ITSELF BE a 'current', because a 'charged' (or separated plasma) is no longer neutral, and so any MOVEMENT of such separated/charged plasma would in effect BE 'a current' of 'like' charges of only ONE kind (ie, either " " OR "-").
Neutral plasma moves as a 'body' of both charges. A separated plasma of only 'like charges' (all electrons OR all protons) is in effect a 'current' of 'like charges', not a simple plasma. :)
Bye
Fleetfoot
5 / 5 (1) Oct 02, 2012
it is plasma, and as such will have an electrical charge, it must or it's not plasma.


Reality, I don't think your definition of plasma is correct, this is how plasma physicist Anthony Peratt describes plasma:

"Plasmas are conductive assemblies of charged particles, neutrals and fields that exhibit collective effects. Further, plasmas carry electrical currents and generate magnetic fields."


What you quote is correct, but it doesn't say the plasma has to be charged to be classed as plasms. What matters is that it must be a gas which is mostly ionised but in general it will be neutral overall.

Not trying to nit pick, but there are some misconceptions about plasma, especially plasmas in space.


Indeed, you just demonstrated your own. For the neutral plasma on the dwarf's surface, magnetic fields would be important but not electrostatic effects.

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