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Just like corporations, stars, too, can engage in mergers and acquisitions: a new study has identified a pair of white dwarf stars heading toward a merger.
White dwarfs are the hot, superdense remnants of spent stars. In a binary system called J0651, two white dwarfs circle each other very rapidly. The binary pairing completes an orbit in less than 13 minutes.
And that already rapid orbital dance is speeding up as the two white dwarfs spiral in on each other. Each year their orbital period shrinks by 0.3 milliseconds. That’s actually a pretty dramatic change on astronomical timescales.
In about a million years, the white dwarfs will get so close that the larger one will start to cannibalize its smaller companion. Before long, the two stars will likely become one. The study appears in the Astrophysical Journal Letters. [J.J. Hermes et al, Rapid Orbital Decay in the 12.75-minute Binary White Dwarf J0651+2844]
The tightly wound white dwarf binary should also be radiating gravitational waves—ripples in the fabric of space and time. But today’s gravitational wave detectors are not sensitive enough to detect them. That’s okay—astronomers have another million years, before things get really interesting, to build an instrument that’s up to the task.
—John Matson
[The above text is a transcript of this podcast.]
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18 Comments
Add CommentMy curiosity became aroused when I read above that "In about a million years, the white dwarfs will get so close that the larger one will start to cannibalize its smaller companion. Before long, the two stars will likely become one."
Reply | Report Abuse | Link to thisWhite dwarfs are composed of matter so dense that electrons can no longer orbit their nuclei - atoms decompose into free electrons and nuclei, compacted far beyond the limits of atomic matter. I had to wonder whether one (even more massive) white dwarf could possibly strip material from another, since white dwarfs are individually limited to ~1.4 Solar masses (they would otherwise have gone supernova).
I found the freely available preprint archive version of this report at:
http://arxiv.org/pdf/1208.5051v1.pdf
Searching the research document, I found no mention of the text, 'cannibal' or any other mention that the larger white dwarf might be able to accrete electron-degenerate material from the smaller one.
I found the following statement in
http://en.wikipedia.org/wiki/Type_Ia_supernova#Double_degenerate_progenitors
"The missing radiation indicates a lack of accretion discs around white dwarfs, ruling out the common, accretion-based model of Ia supernovae."
While a very brief period of 'cannibalization' right before supernova occurred might be possible, I found no mention of it.
The very next statement in that Wikipedia entry is that "The inwards spiraling white dwarfs must be strong sources of gravitational waves, but this can't be detected as of 2012."
As this podcast mentions, the main point of the referenced research report is that this merging white dwarf binary is estimated to be the second-most "brightest" source of gravitational waves in the sky - an excellent candidate for some future [space] mission to measure gravitational waves.
The next statement in the Wikipedia entry is:
"Double degenerate scenarios raise questions about the applicability of Type Ia supernovae as standard candles, since total mass of the collapsing star made by the two white dwarfs vary on a great range, meaning luminosity also varies."
The recent discovery that many more double degenerate type Ia SNe may be occurring that had previously been thought seems to raise questions about the studies of type Ia SNe that presumed them to be reliable standard candles - and concluded that the expansion of the universe has been accelerating for about 5 billion years...
Oh, these are very interesting times!
@ jtdwyer.
Reply | Report Abuse | Link to thisTo me seems that the very concept of cannibalization of white dwarf stars (one eaten by another) is what is causing your objection of the term used in the podcast. You mention in your comment the term (not used in the podcast) *strip material* in the phrase, *I had to wonder whether one (even more massive) white dwarf could possibly strip material from another, ...*
My point is that if the merger of the largest white dwarf star and the smallest occur in two billion years it could be metaphorically named cannibalism. The remnant star, in this interpretation, will be more voluminous (fat?), of course. The star (He or She?) will explode after the cannibalization? But if so this will be a fact posterior to the act of *eat*.
The web page below brings this information:
http://www.cfa.harvard.edu/news/2012/pr201225.html
*The stars will eventually merge, in two million years. Future observations will continue to measure the orbital decay of this system, and attempt to understand how tides affect the merger of such stars.*
@abrasileirosilva
Reply | Report Abuse | Link to thisCorrection: Not in two billion years, but in two million years!
Most curious! No, I'm not having edification issues, I'm simply wondering whether the gravitation of the larger star would be sufficient to remove exceedingly dense electron-degenerate material from the smaller.
Reply | Report Abuse | Link to thisBy the way, your reference article also makes no mention of these or any other binary white dwarf stars accreting any material from one another. I've only found that process being suggested in this podcast: I suspect it's in error, which is why I brought it up.
The article text actually states:
"In about a million years, the white dwarfs will get so close that the larger one will start to cannibalize its smaller companion. Before long, the two stars will likely become one."
Please see:
http://en.wikipedia.org/wiki/Binary_stars#Mass_transfer_and_accretion
Also see:
http://en.wikipedia.org/wiki/Type_Ia_supernova#Formation
The consensus model type Ia supernova occurs when a white dwarf accretes matter from a companion star. This is thought to most often occur when the companion star itself becomes a red giant, swelling up and expelling its outer material into space. When the white dwarf accretes sufficient mass to reach 1.4 Solar masses it collapses, forming a supernova.
In the case of "double degenerate progenitors" the final process is described as a collision or merger - no accretion is mentioned. In the case of two white dwafs merging, there will be no surviving 'cannibal' - the product of the merger will immediately produce an enormous supernova.
The principle reasoning behind my question is that, in the consensus type Ia SN model the white dwarf accretes the companion's material that is being released into space: it does not 'suck' matter off of the companion star - I think certainly not if the companion was also a white dwarf composed of super-dense electron-degenerate matter. I have no other significant issues with any terminology or interpersonal relations between two consenting adults, etc. - thanks for your concern.
The article states that
Reply | Report Abuse | Link to this"The tightly wound white dwarf binary should also be radiating gravitational waves—ripples in the fabric of space and time"
An inquisitive mind will raise a query -- " in what fabric of space-time, gravitational waves will be created?"
Of late, it has become fashionable in cosmology to use the term "fabric of space -time". When mainstream scientific theories considers physicality of space as Nil, how gravitational waves can create some physical ripples in fabric which has no physicality?
I agree with the reservations, as expressed by jtdwyer, regarding mergers of the white dwarf binary system J0651 in future after about 2 million years. Both white dwarfs are encircling each other with orbital period of 13 minutes. Some other sources indicate that white dwarfs are encircling each other at a distance of about 1/3rd of the distance between earth and moon and binary system is located at distance of about 3000 light years from earth. These distance are quite small distances compared to astronomical standards.
Reply | Report Abuse | Link to thisi) I wonder why so far larger white dwarf has not accreted matter from small white dwarf to explode into a SN ? Since the system is located at only 3000 light years, had it been exploded as a SN, it could have been observed at earth
ii) J-0651 is located at distance of 3000 light years and a white dwarf is an ultra dense object. If the system has been really radiating gravity waves, why no gravity wave detectors on earth has detected gravity waves being created at a not very large distance of 3000 light ears? Do gravity waves become really too week on reaching earth to evade detection by current gravity detectors OR the concept of gravity wave per se is an elegant scientific speculation?
@ jtdwyer.
Reply | Report Abuse | Link to thisYou are in contradiction with yourself. In your first comment you said this:
*While a very brief period of 'cannibalization' right before supernova occurred might be possible, I found no mention of it.*
And in your second comment you said this:
*In the case of two white dwa(r)fs merging, there will be no surviving 'cannibal' - the product of the merger will immediately produce an enormous supernova.*
Perhaps a terrible *indigestion* could be responsible for that explosion.
Your statement that *I have no other significant issues with any terminology or interpersonal relations between two consenting adults, etc.* not convinces me and seems nonsensical. The terminology *cannibalization* or *cannibalize* used in the podcast , in the article that I cited and in my and in your first comment is about the relation of one PREDATOR and its PREY. No mention in my comment about *relations about two consenting adults*.
What I said plainly understandable is not about sex or cannibalism between degenerated persons.
I hope that our friendly debate generates enlightenment and not merely heat!
IMO, its a moot point of semantics. Sorry.
Reply | Report Abuse | Link to thisTo hopefully be perfectly clear, the intent of my comment was to dispute the assertion made in this podcast that, at some point, one white dwarf will remotely accrete material from the the other.
Reply | Report Abuse | Link to thisI think that this will never occur, except in some sense at the moment of collision, when the two discrete objects of mass make contact, before their combined material might merge to form a single spherically symmetrical object of mass.
However, I expect that at some point prior to the completion of the merger, the combined mass of the two objects will produce an enormous supernova...
First, in the interest of clarity I must point out that the term 'gravity wave' is technically distinct from a 'gravitational wave'. The two are for obvious reasons easily confused - the terms should therefore never be used interchangeably.
Reply | Report Abuse | Link to thisA gravity wave is, in fluid dynamics (unfortunately), a wave imparted by gravitational influences on the interface between two distinct fluids - such as the ocean and the atmosphere, for example.
Secondly, while this article describes gravitational waves as "ripples in the fabric of space and time," IMO this 'fabric of spacetime' is merely an unfortunate analogy that can be used by anyone to envision how gravity works by curving some undescribed dimensional 'fabric.' However, I'm afraid that everyone is also able to visualize this in any way they like.
A gravitational wave should be considered to be a wave signal in the curvature of spacetime described by general relativity. GR very accurately describes the effects of gravitation through changes imparted to an abstract system of dimensional coordinates within spacetime. While, as you say, there is no physical fabric or medium described upon which this curvature is imparted.
Be that as it may, since the effects of gravitation are usefully described as a gradient field of spacetime dimensional coordinates, a gravitational wave produced by rapidly orbiting very massive objects would be a periodic disturbance or signal in the gravitational field of abstract dimensional coordinates. Whatever the undescribed physical elements might be that are represented by those abstract coordinates, that is not necessarily relevant to the discussion of gravitational waves.
If we imagine that, through some black magic, that the Moon's suddenly began to rapidly jump to half its normal distance from the Earth and then back again, repeatedly, it can be imagined that, just like the relatively gentle fluctuations in the Moon's gravitational effects know as tidal effects on the ocean, the ocean would suddenly begin to violently vibrate. Those violent vibrations would be the product of gravity waves - a waving of the effects of gravitation.
(continued)
Reply | Report Abuse | Link to thisIf you imagine being on a spaceship in a parallel circular orbit around the rotating J0651, every ~6.5 minutes (modified by your own orbital velocity) the pair of white dwarfs would appear side by side, at their furthest distance. About 6.5 minutes later, only one would be visible, at it's nearest position relative to you. Those two distinct configuration of mass (although actually a continuously repeating series of mass configuration variations) would produce distinct gravitational effects, continuously varying the gravitational effects imparted to your spacecraft - a very bumpy ride.
Regardless of what the undescribed physical elements of spacetime are involved in the production of gravitational effects, gravitational waves imparted directly to those effects may be possible. However, their precise nature has not yet been determined. While it must be expected that the amplitude of gravitational waves must diminish as a function of distance propagated, the precise nature of the propagated signal may depend on the influence of other signals.
For example, there is some speculation of a gravitational wave background, analogous to the EM CMB. Since (diminishing) gravitational waves are thought to propagate perpetually, there could be a stochastic background of gravitational waves, produced by the interactions of all gravitational wave signals.
As gravitational waves from all diminishing signals interact over time and distance, it may (as I suspect) become impossible to remotely detect even a very strong, relatively nearby (3klya) signal from all the background noise - not to mention any gravitational waves produced by that child jumping up and down near your Earthbound detector...
@jtdwyer (9)
Reply | Report Abuse | Link to thisTwo white dwarfs in close proximity, as in the case of system J0651, can either convert to a SN or merge to form a larger massive object. How can such white dwarfs approach both ways -- SN and merger? In my view, if all the conditions of mass ( 1.4 times the mass of Sun) are fulfilled, larger white dwarf should accrete matter from smaller white dwarf and explode as a SN. Due to its higher gravitational force, it should be capable of attracting matter on to nitself from the outer layers of smaller white dwarf. If we say that larger white dwarf may not be able to attract matter on to itself from small white dwarf, due to matter being tightly held in small white dwarf, same issues may arise in case of mergers also. In case of mergers also, matter from small white dwarf shall be attracted to larger white dwarf. Then what will be the nature of resulting object on merger? will it be necessarily a bigger white dwarf on merger or some other star?
Read my first comment - read the following linked reference:
Reply | Report Abuse | Link to thisI found the following statement in
http://en.wikipedia.org/wiki/Type_Ia_supernova#Double_degenerate_progenitors
"The missing radiation indicates a lack of accretion discs around white dwarfs, ruling out the common, accretion-based model of Ia supernovae."
Why do I always have to repeat myself for you?
@jtdwyer (10 and 11)
Reply | Report Abuse | Link to thisThanks for your detailed elaboration on the concept of gravitational waves.
"how gravity works by curving some undescribed dimensional 'fabric.'"
"Regardless of what the undescribed physical elements of spacetime are involved in the production of gravitational effects, gravitational waves imparted directly to those effects may be possible. However, their precise nature has not yet been determined."
If precise nature of undescribed dimensional fabric of space or physical elements of space has not been determined, that was not the issue of much concern.The issue which is of major concern, which I can not comprehend, is that some scientists, belonging to even mainstream schools of thought, consider physicality of space as NIL. If physicality of space is NIL ( NIL implies really nil not comprising of any physical entity), how gravitational waves could be physical reality?
How interaction of propagating gravitational waves ( within amongst themselves and with e.m signals)could be an impediment in their detection? If some gravitational waves interact with other gravitational waves, such interaction should lead to some effects parallel to optical effects ( like reflection, refraction, diffraction, interference) as in case of e.m waves. If gravitational waves interact with e.m waves, there should be change in energy of signal of e.m wave. Otherwise, what is the meaning of interaction ? If direct inter-actional effects of gravitational waves, generated at comparatively small distance of 3000 light years, are not detectable, what can be said about detection of impact upon CMB, from background gravitational waves which were created long ago some 13.72 billion years in the past. But none of these effects so far have been ascertained by scientists. In view of this, existence of gravitational waves remains in cloud
The rotating masses of J0651 are expected to produce a variation or signal of a specific amplitude and frequency in detected gravitation. See
Reply | Report Abuse | Link to thishttp://en.wikipedia.org/wiki/Gravitational-wave_detector
If background gravitational waves variously destructively and/or constructively interfere with the signal from J0651, there may be no identifiable signal that can be detected from J0651. The result would be the analogous to the static produced by spurious background radio signals interfering with analog radio & TV receivers tuned to a distant transmission station.
I made no mention of EM waves here - they are waves of electromagnetic energy having nothing to do with any waving of gravitational effects.
"If background gravitational waves variously destructively and/or constructively interfere with the signal from J0651, there may be no identifiable signal that can be detected from J0651"
Reply | Report Abuse | Link to thisYes, I agree that signal from J0651 may lose its original character on interfering ( constructively or destructively) with background gravitational signal. But interference can not be a cause for non-detection of gravitational waves from J0651 . A superimposed gravitational signal from J0651, after interfering with signal from background gravitational, shall exist and persist very much. On the contrary, in case of constructive interference, strength of gravitational signal from J0651 system should become stronger.
Regarding interaction between e.m waves and gravitational waves, I made the observations in the context of scientist's speculation on the impact of background gravitational waves ( before surface of last scattering) upon CMB signals which are e.m in character. If it is established that background gravitational signals, as appearing in the universe before surface of last scattering, have impacted CMB signals, this will also establish the principle that gravitational waves and e.m waves are interacting. In such case, gravitational waves created at any place at any time from any source shall impact e.m signals, which come in contact with those gravitational waves, and this effect be detectable.
But neither of above detection has been made for gravitational waves generated at even closer distance of 3000 light years
"If background gravitational waves variously destructively and/or constructively interfere with the signal from J0651, there may be no identifiable signal that can be detected from J0651."
Reply | Report Abuse | Link to thisI'm no expert, but before you summarily dismiss potential disruptive effects of interfering gravitational waves...
The radiation background includes much more than just primordial emissions, including many distant radio transmitters, nearby electric motors, power lines, etc. It's estimated that the noisy signal from an 'untuned' radio receiver consists of around 1% primordial background radiation with the remainder coming from many other disperse sources, depending on conditions at the receiver's location.
It is these spurious signals from many discrete directions that can interfere with the emissions from a distant discrete source - over its entire propagation distance.
As I understand, constructive interference only amplifies another signal if they are of identical wavelength and originating from proximal transmission sources. Otherwise, only some waves may be amplified, others diminished, effectively producing a potentially indecipherable noisy signal.
I'll have to dismiss the remainder of your unsupported contradictions without further consideration - I don't have the energy to explain everything you question.
@vinodkumarsehgal
Reply | Report Abuse | Link to thisin reply to your question,
" in what fabric of space-time, gravitational waves will be created?"
Of late, it has become fashionable in cosmology to use the term "fabric of space -time". When mainstream scientific theories considers physicality of space as Nil, how gravitational waves can create some physical ripples in fabric which has no physicality?
if you want to take the mainstream stance on non physicality you can, but that limits the possible explanations to the question.
True that current instrumentation has yet to detect physicality of space time, but on the quantum level just because something hasn't been observed doesn't mean the outcome answer is non existence.
science is based on observation (which weighs heavy on perception and an observer. ) while in all actuality, reality (and defining observation of it) is in a constant state of flux until the effect is observed.