Starship Asterisk*

Ron-Astro Pharmacist wrote:
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.

ta152h0 wrote:where is Rube Goldberg when we need him ?

Dunionstronomy wrote:

This gives me a wacky idea: Quasar-imitative energy apparatus. Is it remotely feasible to consider a possible generator or source of energy using an quasar-imitative physical machine, which is able to draw from a tank dense with energy into an accelerator that acts as a turbine to expel jet-like waves of protons and electrons in order to provide power and energy for lights or machines etc. Perhaps even create a powerful laser to correct telescopic/other discrepancies in Earth's orbit, such as the mission where the Hubble lens discrepancy was fixed many years ago?

...On a side note, the concept behind the illustration (quasar) is such a baffling notion, predominantly the idea that the jets of energy can escape the event horizon.

Although, is it possible for the rotation of a disk centered around the massive gravity of a singularity to gain enough momentum to travel faster than the speed of light? This does not make physical sense, although it seems possible, since light cannot escape the singularity beyond the event horizon. For this reason, shouldn't the gravitational pull of the singularity be able to accelerate surrounding matter or provide enough force to exceed light-speed?

...

bystander wrote:
Black Hole Boasts Heavyweight Jets
ESA | Space Science | XMM-Newton | 2013 Nov 13

Black Hole Jets Pack a Powerful Punch
Commonwealth Scientific and Industrial Research Organisation (CSIRO) | 2013 Nov 14

New Data on Composition of Relativistic Jets from Black Holes
University of Barcelona | 2013 Nov 14

• Nature (online 13 Nov 2013) DOI: 10.1038/nature12672
  arXiv.org > astro-ph > arXiv:1311.5080 > 20 Nov 2013

JohnD wrote: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

BDanielMayfield wrote:

Just_Jackson wrote: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.

Nitpicker wrote:

Bardeen-Petterson Effect.JPG (38.44 KiB) Viewed 3895 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

Chris Peterson wrote: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.

Chris Peterson wrote:

BDanielMayfield wrote: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.

alter-ego wrote:

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

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

Ann wrote: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.

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

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

http://en.wikipedia.org/wiki/Black_hole#X-ray_binaries wrote: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.

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

Chris Peterson wrote:

Cousin Ricky wrote: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.

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.

Boomer12k wrote:Oh....My bad....poor old demented brain not getting enough oxygen or something....

Boomer12k wrote: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....

:---[===]*

BDanielMayfield wrote: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.

JohnD wrote: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 wrote: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?)

Anthony Barreiro wrote:

MarkBour wrote: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.