APOD: Heavy Black Hole Jets in 4U1630 47 (2013 Nov 20)

[BDanielMayfield]

In the artist's depiction, what is the bright spot where the streamer from the star joins the accretion disc?

That bright spot would be the place where gas falling from the companion star hits the rapidly rotating outer edge of the accretion disk. Friction from this collision is what would cause this point to be white hot. The rotation rate gets faster and faster of course as the gas/plasma in the accretion disk spirals toward the black hole. Friction between particles heats this material again as it migrates toward the inner edge of the disk.

I had asked how hot this material in the disk could become; to address questions of weather fusion might be occurring there.

The maximum temperature for an accretion disc around a small black hole is around 10[super]7[/super] K.

So if the temp maxes out at about only 10^7 K then only light nuclei fusion could be possible. The Fe and Ni being shot out the jet at 2/3rds c must have come from the companion star, although probably almost all of it would have been created in the BH’s progenitor.

[Tara_Li]

Unless this star is very unusual, it is going to contain heavy metals, up to and including iron - and probably even a bit beyond. Iron contained in the star material gets drawn off into the accretion disk, spirals in and gets ejected in the disk... Who honestly *DIDN'T* expect to see iron & nickel in the jets?

I was under the impression that the reason it's unexpected is because the jets move at such speeds that the heavier stuff wouldn't be in them since it takes that much more energy to accelerate a heavier object.

Being heavy, the iron would mostly reside deep within the scavenged star and, hence, not be readily available in the material drawn off into the black hole accretion disk.[/quote]

Sorry, but there is *some* heavy element contamination at all levels. Otherwise, we wouldn't detect it in the solar spectrum. There are Fraunhofer lines all the way up to mercury and gold, at least! So, while the majority of the heavy elements tend to stay deeper, the photosphere appears to be 0.16% iron by mass (see Wikipedia article on the Sun for specific references). It's not like these are bulk quantities - they're for the most part atomic vapor, and the settling is likely not that strong. So, again - I see no reason at all not to expect significant amounts of these ions in the jets. To counter-act their greater mass, they carry a much higher electric charge per nucleus, so that would make magnetic fields more effective in corralling them into the outflows.

[Ron-Astro Pharmacist]

The inital question was "What are black holes made of"? I can’t keep my overactive curiosity to myself so I’ll put it out there.

If photons do have a super-symmetric partner; the photino and that partner is somehow related to dark matter, why couldn’t a black hole be a congregation of dark matter? The ejection of the “non-dark matter” in these relativistic jets is the only thing we can really measure, isn't it?

It sounds crazy but in searching you find results such as:

http://link.springer.com/article/10.100 ... (2011)025#

A journal I read all the time. Obviously it does spark my imagination. A little knowledge is a terrible thing to mind so please excuse my ignorance.

The idea that these jets contain leptonic (is that a word?) and baryonic matter is quite interesting. Probably not in the way I seem to imagine. Could SUSY have the last word on the matter? Pun intended.

[Ron-Astro Pharmacist]

Black hole "jets" was the intial question. I guess I had black holes "on my mind" Ron

[Chris Peterson]

If photons do have a super-symmetric partner; the photino and that partner is somehow related to dark matter, why couldn’t a black hole be a congregation of dark matter? The ejection of the “non-dark matter” in these relativistic jets is the only thing we can really measure, isn't it?

It's unlikely that there's much dark matter in a polar jet (or falling into black holes) for the simple reason that there's no mechanism to cause dark matter to either lose or gain energy in the vicinity of a black hole. So it wouldn't form a disc, it wouldn't infall, and it wouldn't be subject to the magnetic effects presumably at the heart of the jet formation mechanism.

What jets are made of is known to some extent: definitely electrons, some light nuclei, and now apparently, some heavier nuclei. Nothing exotic, and really, there's no reason to expect anything exotic.

[Anthony Barreiro]

Actually, here's a question related to JohnD's that I cannot answer. When looking at jets from BH's we are really talking about material that never entered the BH. So, the jets are really pointed in a direction dependent on the angular momentum of the matter that swirls around but never enters a BH. But does this also determine or influence the angular momentum of material inside the BH as well? Or can it possibly occur that the angular momentum of the BH is independent of and quite different from the angular momentum in the accretion disk?

Nobody has ever measured the spin (as opposed to the mass) of a black hole directly. This is still a very active area of research with only indirect means of measuring the spin of a black hole, and competing theories. According to an interesting article about black hole spin rates from sky and telescope a couple of years ago, the spin of the black hole should influence the strength of the jets. If the black hole is spinning in the same direction as the accretion disk, the jets will be more powerful, and if the black hole is spinning in the opposite direction to the accretion disk, the jets will be much less powerful.

[JohnD]

And Mark Bour's post raises the question - does the axis of spin of a BH always coincide with the axis of the accretion disc?
John

[Nitpicker]

I've learnt a lot about relativistic jets since this APOD was published less than a day ago, thanks largely to the variety of comments it has generated, which have in turn inspired me to read more on the subject.

It seems this APOD is not so much about what black holes are made of, and more about what they're not.

It is really about the relativistic jets of plasma, which are propelled by electromagnetic force, which is induced by fast-rotating, helical magnetic fields, which are generated by fast-rotating accretion disks -- primarily of electrically charged plasma, and including ions (of uncertain origin and concentration) as heavy as Fe and Ni (i.e. the largest binding energy per nucleon) -- which form gravitationally in x-ray binary systems like 4U1630-47, around the compact accretor.

The jets don't seem to interact with the compact accretor. Indeed the compact accretor does not even have to be a black hole, from what I have read. Is there a criterion for knowing whether the compact accretor is a black hole, or a neutron star or a white dwarf?

(And do we know how far away this system is?)

[Chris Peterson]

And Mark Bour's post raises the question - does the axis of spin of a BH always coincide with the axis of the accretion disc?

This is generally assumed, but simulations support the possibility of tilted accretion discs, and suggest observational tests to identify them. I don't think any model allows for jets to be anything but polar, however.

[BDanielMayfield]

Actually, here's a question related to JohnD's that I cannot answer. When looking at jets from BH's we are really talking about material that never entered the BH. So, the jets are really pointed in a direction dependent on the angular momentum of the matter that swirls around but never enters a BH. But does this also determine or influence the angular momentum of material inside the BH as well? Or can it possibly occur that the angular momentum of the BH is independent of and quite different from the angular momentum in the accretion disk?

Nobody has ever measured the spin (as opposed to the mass) of a black hole directly. This is still a very active area of research with only indirect means of measuring the spin of a black hole, and competing theories. According to an interesting article about black hole spin rates from sky and telescope a couple of years ago, the spin of the black hole should influence the strength of the jets. If the black hole is spinning in the same direction as the accretion disk, the jets will be more powerful, and if the black hole is spinning in the opposite direction to the accretion disk, the jets will be much less powerful.

Thanks for the link to the S&T article Anthony. Reading it helped me to begin to get a tenuous handle on how magnetic fields can redirect material from the inner edge of BH accretion disks into the disks.

[BDanielMayfield]

I've learnt a lot about relativistic jets since this APOD was published less than a day ago, thanks largely to the variety of comments it has generated, which have in turn inspired me to read more on the subject.

It seems this APOD is not so much about what black holes are made of, and more about what they're not.

It is really about the relativistic jets of plasma, which are propelled by electromagnetic force, which is induced by fast-rotating, helical magnetic fields, which are generated by fast-rotating accretion disks -- primarily of electrically charged plasma, and including ions (of uncertain origin and concentration) as heavy as Fe and Ni (i.e. the largest binding energy per nucleon) -- which form gravitationally in x-ray binary systems like 4U1630-47, around the compact accretor.

The jets don't seem to interact with the compact accretor. Indeed the compact accretor does not even have to be a black hole, from what I have read. Is there a criterion for knowing whether the compact accretor is a black hole, or a neutron star or a white dwarf?

(And do we know how far away this system is?)

And thank you too Nitpicker. Your post helps as well. Excellent summation and chain of causation.

[BDanielMayfield]

And Mark Bour's post raises the question - does the axis of spin of a BH always coincide with the axis of the accretion disc?
John

Mark and John, consider how the accretion disks of SMBH’s at galactic cores must change over time as material falls into them from all angles. The orientation of the current accretion disk is caused by whatever has been feeding it recently, while the black hole's spin is the sum of the angular momentum of everything that has become a part of it since its origin. Therefore I’d say the answer would be definitely no.

Bruce

[Chris Peterson]

Mark and John, consider how the accretion disks of SMBH’s at galactic cores must change over time as material falls into them from all angles. Therefore I’d say the answer would be definitely no. The orientation of the current accretion disk is caused by whatever has been feeding it recently, while the black hole's spin is the sum of the angular momentum of everything that has become a part of it since its origin.

That assumes that there is no stabilizing force from the spinning black hole itself to maintain the orientation of the accretion disc in alignment with the black hole's axis. In fact, such things exist (e.g. the Bardeen-Petterson effect). It is doubtful that accretion discs (especially thin ones) deviate too far from the equatorial plane of the rotating compact body, or stay tilted for long periods.

[Boomer12k]

Nature's way of spreading Star Seeds??? As well as the Impending Type 1A Supernova??? Assuming there is a companion dwarf drawing that off....

The Universe never stops amazing me....

:---[===]*

Oh....My bad....poor old demented brain not getting enough oxygen or something....DUH.....BLACK HOLE.....NOT A DWARF STAR!!!!!! Alert....Alert....BRAIN CLOUD!!!!

OK...all ready had some event here, got some heavy metals....did not really click until I read Mayfield's Post...Thanks for the Wake Up Call....
But then you have a supernova event...and collapse to a black hole, because of sufficient mass....the accretion disc is coming from...as illustration shows...the larger companion....that means that these elements are not formed in that Supernova....but would form from the Companion...as the other star is Kaput....JA????
So, this must be new material....not old from the previous star....as material cannot leave the Black Hole....
Hope I did better that time....

:---[===] *

[Beyond]

Oh....My bad....poor old demented brain not getting enough oxygen or something....

NAH You haven't quite adjusted to seeing things through your downsized :---[===]*, yet.

[Ann]

I haven’t seen very many detailed paintings of blue stars, but on those that I have seen, the stellar prominences (and chromospheres, for that matter) are depicted in blue. Don’t prominences get their color from H-alpha emissions? Wouldn’t they be red regardless of the star’s temperature?

The color of a prominence depends on the atoms that are ionized. Prominences aren't really red... reddish would be a better description, since Ha is only one of the emission lines. Still, a several solar mass blue star has a hydrogen envelope, so it's prominences should be substantially similar in color to what we see on the Sun.

Note, however, that we only see the color of the prominences of the corona of the Sun during solar eclipses. That is because the solar disk is so much brighter than the prominences. The blue star in today's APOD isn't eclipsed, and its disk is much, much brighter than the disk of the Sun. Admittedly its prominences would likely also be brighter than the prominences of the Sun, but still, a picture like this shouldn't realistically show prominences of the corona. We do seem to see the prominences, and if we do see them they should be reddish in color, as Chris said. But in my opinion we shouldn't see them at all.

Do blue giants show limb-darkening?

I can't think of any reason they wouldn't. But keep in mind that limb darkening is essentially a continuum phenomenon. In narrow spectral bands, it may not be present, or you can even get limb brightening. And this artistic representation pretty clearly shows the blue star as it would appear in some narrow band, not white light.

I don't find the color of this blue star very unrealistic (except for the blue prominences), so in my opinion, this could be a "white-light picture". The problem is that the star is not nearly bright enough. Hot blue stars have fantastically bright photospheres. The illustration makes the star look almost dark in places, which is beyond impossible. A closeup of a blue star like this one would be so overwhelmingly bright that we wouldn't be able to see the accretion disk of the black hole at all, except its innermost, very bright parts.

Ann

[Nitpicker]

Is there a criterion for knowing whether the compact accretor is a black hole, or a neutron star or a white dwarf?

To let Wikipedia answer my question ...

X-ray binaries are binary star systems that are luminous in the X-ray part of the spectrum. These X-ray emissions are generally thought to be caused by one of the component stars being a compact object accreting matter from the other (regular) star. The presence of an ordinary star in such a system provides a unique opportunity for studying the central object and determining if it might be a black hole.

If such a system emits signals that can be directly traced back to the compact object, it cannot be a black hole. The absence of such a signal does, however, not exclude the possibility that the compact object is a neutron star. By studying the companion star it is often possible to obtain the orbital parameters of the system and obtain an estimate for the mass of the compact object. If this is much larger than the Tolman–Oppenheimer–Volkoff limit (that is, the maximum mass a neutron star can have before collapsing) then the object cannot be a neutron star and is generally expected to be a black hole.

...

(And do we know how far away this system is?)

Anybody?

[alter-ego]

(And do we know how far away this system is?)

In round numbers, it's tabulated (2004) here to be 33,000 Ly,

[Chris Peterson]

I don't find the color of this blue star very unrealistic (except for the blue prominences), so in my opinion, this could be a "white-light picture". The problem is that the star is not nearly bright enough. Hot blue stars have fantastically bright photospheres. The illustration makes the star look almost dark in places, which is beyond impossible. A closeup of a blue star like this one would be so overwhelmingly bright that we wouldn't be able to see the accretion disk of the black hole at all, except its innermost, very bright parts.

This artistic interpretation, like most, looks nothing at all as the scene would appear to our eyes. The colors are far too saturated, and a huge dynamic intensity range has been flattened almost to nothing. We should look at images like this in terms of the physical system being described, and view the colors and intensities as little more than keys to temperature and brightness.

[Nitpicker]

(And do we know how far away this system is?)

In round numbers, it's tabulated (2004) here to be 33,000 Ly,

Thank you alter-ego, round numbers are my favourite. That would put it a bit past the galactic centre, not far from the observation shadow (obviously far enough).

Looking at that list, and how many closer and perhaps more energetic x-ray binary/stellar-mass black hole candidates there are (not to mention the large number of more massive black hole candidates), it makes me wonder if the emission of heavy atomic nuclei from relativistic jets is an uncommon occurrence, or whether a new technique has made this recent discovery possible (or both). I suppose orbiting x-ray observatories are rather new and decent radio interferometers aren't exactly mass-market items.

[BDanielMayfield]

Mark and John, consider how the accretion disks of SMBH’s at galactic cores must change over time as material falls into them from all angles. Therefore I’d say the answer would be definitely no. The orientation of the current accretion disk is caused by whatever has been feeding it recently, while the black hole's spin is the sum of the angular momentum of everything that has become a part of it since its origin.

That assumes that there is no stabilizing force from the spinning black hole itself to maintain the orientation of the accretion disc in alignment with the black hole's axis. In fact, such things exist (e.g. the Bardeen-Petterson effect). It is doubtful that accretion discs (especially thin ones) deviate too far from the equatorial plane of the rotating compact body, or stay tilted for long periods.

Thanks Chris. I was certain alright, although I was certainly wrong. In hindsight, ! Naturally there would be a magnetic coupling of forces from the spinning BH’s intense magnetic field and the highly charged accretion disk. So no matter what direction new material falls in from, in time the disk and the BH’s spin would have to re-align.

[Nitpicker]

That assumes that there is no stabilizing force from the spinning black hole itself to maintain the orientation of the accretion disc in alignment with the black hole's axis. In fact, such things exist (e.g. the Bardeen-Petterson effect). It is doubtful that accretion discs (especially thin ones) deviate too far from the equatorial plane of the rotating compact body, or stay tilted for long periods.

If, like me, you are curious as to what the Bardeen-Petterson effect is, read on. I have just learnt that it is "the combined action of the Lense-Thirring effect and the internal viscosity of the accretion disc", which forces the inner part of the disc to align with the axis of the compact accretor's rotation. The outer parts of the disc may still remain out of alignment with the compact accretor, and the resulting transition between the inner and outer regions of the disc is thought to be the cause of periodic fluctuations in the x-ray signals observed from some systems.

Here is a schematic:

a44fig01.gif (28.43 KiB) Viewed 3903 times

The above picture is from:
http://www.scielo.br/scielo.php?pid=S01 ... ci_arttext

See also:
http://en.wikipedia.org/wiki/Lense%E2%8 ... precession

(And I might also refer to the tendency of Starship passengers to learn new things, as the Peterson effect.)

[alter-ego]

Bardeen-Petterson Effect.JPG (38.44 KiB) Viewed 3896 times

The above picture is from:
http://www.scielo.br/scielo.php?pid=S01 ... ci_arttext
See also:
http://en.wikipedia.org/wiki/Lense%E2%8 ... precession

I'm surprised. My intuition about black holes is better than I thought. Upon thinking about a misaligned accretion disk, my first visualization was a warped disk that doesn't rotate uniformly, but rather precesses in a perturbed manner.

[JohnD]

In the artist's depiction, what is the bright spot where the streamer from the star joins the accretion disc?

That bright spot would be the place where gas falling from the companion star hits the rapidly rotating outer edge of the accretion disk. Friction from this collision is what would cause this point to be white hot. The rotation rate gets faster and faster of course as the gas/plasma in the accretion disk spirals toward the black hole. Friction between particles heats this material again as it migrates toward the inner edge of the disk.

Following the link in the original blurb on "recent evidence" gets to this site http://www.csiro.au/Portals/Media/Black ... punch.aspx where a crude video illustrates this situation. It shows a 'bright spot' far inside the accretion disc. Is this artist's licence, put in to show the rotataion of the disc, or what?

John

[Nitpicker]

Following the link in the original blurb on "recent evidence" gets to this site http://www.csiro.au/Portals/Media/Black ... punch.aspx where a crude video illustrates this situation. It shows a 'bright spot' far inside the accretion disc. Is this artist's licence, put in to show the rotataion of the disc, or what?

John

No idea about the orbiting bright spot in that video. But your reminder made me go and read the text in that link -- which I should have done initially -- and that has helped to answer one of my earlier questions. So thanks.