Starship Asterisk*

rstevenson wrote: In the artist's illustration above, there is a small white point of light where the material from the blue giant blends into the orange stream orbiting the black hole. ... what could it represent?

Ann wrote:I'm just guessing, mind you. Could that perhaps be the spot where gas flowing from the blue giant companion hits the swirling accretion disk, so that a lot of energy is produced in that small spot?

neufer wrote:All I can say is that I think the 'artwork' itself was probably based on the Z-PINCH fusion idea (rather than any collision).

BDanielMayfield wrote:That's a fine answer. So, as with many things, the jury is still out, as it were.

The idea of X-ray emission coming from multiple locations within/above accretion disks around a black hole is motivated by the important role of magnetic fields in the process of accretion. The original formulation of the flare model by Galeev et al. (1979) was followed by numerous
papers (e.g. Di Matteo 1998; Nayakshin & Kazanas 2001; Merloni & Fabian 2001; Collin et al. 2003; Goosmann et al. 2007b). A common theme to these models is an underlying assumption of a standard-type accretion flow driving the magnetic field.

Case wrote:

sallyseaver wrote:Please could someone mark the appropriate locations in this APOD image to show the location of: HDE 227018, Cygnus X-1, HDE 226868

Hope this helps.

sallyseaver wrote:Please could someone mark the appropriate locations in this APOD image to show the location of: HDE 227018, Cygnus X-1, HDE 226868

https://en.wikipedia.org/wiki/Lightning wrote:

[b][color=#0000FF][size=150]Distribution of electric charges & lightning strikes in and around a thunderstorm[/size][/color][/b]

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<<When the local electric field exceeds the dielectric strength of damp air (about 3 million volts per meter), electrical discharge results in a strike, often followed by commensurate discharges branching from the same path. Mechanisms that cause the charges to build up to lightning are still a matter of scientific investigation. New study confirming dielectric breakdown is involved. Rison 2016. Lightning may be caused by the circulation of warm moisture-filled air through electric fields. Ice or water particles then accumulate charge as in a Van de Graaff generator.

Unlike the far more common "negative" lightning, positive lightning originates from the positively charged top of the clouds (generally anvil clouds) rather than the lower portion of the storm. Leaders form in the anvil of the cumulonimbus and may travel horizontally for several kilometers before veering towards the ground. A positive lightning bolt can strike anywhere within several kilometers of the anvil of the thunderstorm, often in areas experiencing clear or only slightly cloudy skies; they are also known as "bolts from the blue" for this reason. Positive lightning typically makes up less than 5% of all lightning strikes.

Because of the much greater distance to ground, the positively charged region can develop considerably larger levels of charge and voltages than the negative charge regions in the lower part of the cloud. Positive lightning bolts are considerably hotter and longer than negative lightning. They can develop six to ten times the amount of charge and voltage of a negative bolt and the discharge current may last ten times longer. A bolt of positive lightning may carry an electric current of 300 kA and the potential at the top of the cloud may exceed a billion volts — about 10 times that of negative lightning. During a positive lightning strike, huge quantities of extremely low frequency (ELF) and very low frequency (VLF) radio waves are generated.

As a result of their greater power, as well as lack of warning, positive lightning strikes are considerably more dangerous. At the present time, aircraft are not designed to withstand such strikes, since their existence was unknown at the time standards were set, and the dangers unappreciated until the destruction of a glider in 1999.>>

Ann wrote:And if your'e just white, I ask to to stay well away from me, please! :evil:

BDanielMayfield wrote:

geckzilla wrote:If the plasma created by lightning emits black-body radiation, then, at well over 10000 K, it should be blue.

Really! That just blew my mind! Can't imagine what it must have done to Ann.

geckzilla wrote:If the plasma created by lightning emits black-body radiation, then, at well over 10000 K, it should be blue.

Ann wrote:

https://en.wikipedia.org/wiki/Pinch_(plasma_physics) wrote:
<<A pinch is the compression of an electrically conducting filament by magnetic forces. The conductor is usually a plasma, but could also be a solid or liquid metal. Pinches were the first device used by humankind for controlled nuclear fusion. The phenomenon may also be referred to as a Bennett pinch (after Willard Harrison Bennett), electromagnetic pinch, magnetic pinch, pinch effect or plasma pinch. Pinches occur naturally in electrical discharges such as lightning bolts, the aurora, current sheets, and solar flares.>>

Fascinating, Art. I hadn't really thought of what causes the bright light of lightning bolts. So it is indeed fusion?

Ann wrote:
Some years ago a 14-year-old Swedish girl was knocked unconscious by a bolt of lightning. Otherwise unhurt, she told reporters afterwards: "All I remember is a flash of bright blue light."

So, Art, and others who might know, are lightning bolts typically hot enough to be blue? What temperature are they usually?

geckzilla wrote:If the plasma created by lightning emits black-body radiation, then, at well over 10000 K, it should be blue.

Ann wrote:

neufer wrote: I don't believe that the gas falling from the companion star actually ever "hits" the rapidly rotating outer edge of the accretion disk.

Rather... the gas stream probably smoothly converges into a tight non-intersecting spiral
(with each spiral band moving at approximately the same velocity as its neighboring bands in any event).

I think someone took a close look at the strong confluence taking place at the entry point of the accretion disk spiral and determined that that would be the ideal spot for Z-pinch fusion of hydrogen to occur:

https://en.wikipedia.org/wiki/Pinch_(plasma_physics) wrote:
<<A pinch is the compression of an electrically conducting filament by magnetic forces. The conductor is usually a plasma, but could also be a solid or liquid metal. Pinches were the first device used by humankind for controlled nuclear fusion. The phenomenon may also be referred to as a Bennett pinch (after Willard Harrison Bennett), electromagnetic pinch, magnetic pinch, pinch effect or plasma pinch. Pinches occur naturally in electrical discharges such as lightning bolts, the aurora, current sheets, and solar flares.>>

Fascinating, Art. I hadn't really thought of what causes the bright light of lightning bolts. So it is indeed fusion?

Some years ago a 14-year-old Swedish girl was knocked unconscious by a bolt of lightning. Otherwise unhurt, she told reporters afterwards:

"All I remember is a flash of bright blue light."

So, Art, and others who might know, are lightning bolts typically hot enough to be blue? What temperature are they usually?

Ann

neufer wrote: I don't believe that the gas falling from the companion star actually ever "hits" the rapidly rotating outer edge of the accretion disk.

Rather... the gas stream probably smoothly converges into a tight non-intersecting spiral
(with each spiral band moving at approximately the same velocity as its neighboring bands in any event).

I think someone took a close look at the strong confluence taking place at the entry point of the accretion disk spiral and determined that that would be the ideal spot for Z-pinch fusion of hydrogen to occur:

https://en.wikipedia.org/wiki/Pinch_(plasma_physics) wrote:
<<A pinch is the compression of an electrically conducting filament by magnetic forces. The conductor is usually a plasma, but could also be a solid or liquid metal. Pinches were the first device used by humankind for controlled nuclear fusion. The phenomenon may also be referred to as a Bennett pinch (after Willard Harrison Bennett), electromagnetic pinch, magnetic pinch, pinch effect or plasma pinch. Pinches occur naturally in electrical discharges such as lightning bolts, the aurora, current sheets, and solar flares.>>

neufer wrote:All I can say is that I think the 'artwork' itself was probably based on the Z-PINCH fusion idea (rather than any collision).

• However, I have no idea if it actually is
  or even if the 'artwork' is realistic in regards to the hot spot.

BDanielMayfield wrote:
However, remembering a few times when I've been snookered by the Artful neufer, I must ask: Has this Z-pinch at the outer edge of the accretion disk been confirmed or observed? Perhaps I shouldn't relinquish my earlier notion quite so easily.

Why would gas spilling from the swelling star not fall more directly towards the BH? What would cause a Z-pinch compression at that particular site?

• However, I have no idea if it actually is
  or even if the 'artwork' is realistic in regards to the hot spot.

neufer wrote:

BDanielMayfield, ages ago wrote: 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 don't believe that the gas falling from the companion star actually ever "hits" the rapidly rotating outer edge of the accretion disk.

Rather... the gas stream probably smoothly converges into a tight non-intersecting spiral
(with each spiral band moving at approximately the same velocity as its neighboring bands in any event).

I think someone took a close look at the strong confluence taking place at the entry point of the accretion disk spiral and determined that that would be the ideal spot for Z-pinch fusion of hydrogen to occur:

https://en.wikipedia.org/wiki/Pinch_(plasma_physics) wrote:
<<A pinch is the compression of an electrically conducting filament by magnetic forces. The conductor is usually a plasma, but could also be a solid or liquid metal. Pinches were the first device used by humankind for controlled nuclear fusion. The phenomenon may also be referred to as a Bennett pinch (after Willard Harrison Bennett), electromagnetic pinch, magnetic pinch, pinch effect or plasma pinch. Pinches occur naturally in electrical discharges such as lightning bolts, the aurora, current sheets, and solar flares.>>

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(1) Pinches apply a huge voltage across a tube. This tube is filled with fusion fuel, typically deuterium gas. If the multiplication of the voltage & the charge is higher than the ionization energy of the gas the gas ionizes. (2) Current jumps across this gap. (3) The current makes a magnetic field which is perpendicular to the current. This magnetic field pulls the material together. (4) These atoms can get close enough to fuse.

MarkBour wrote:

Ann wrote:

rstevenson wrote:
In the artist's illustration above, there is a small white point of light where the material from the blue giant blends into the orange stream orbiting the black hole. [What] could it represent? Does the stellar material reach a density sufficient to make it glow before it is torn apart again by the black hole?

Could that perhaps be the spot where gas flowing from the blue giant companion hits the swirling accretion disk, so that a lot of energy is produced in that small spot?

[I'm not trying to create a dispute about the reference to this system (Cygnus X-1), but the article on the Chandra site that I think Art (neufer) got the 2-part illustration from, has as its right panel, an illustration that was actually an earlier APOD: 20 Nov 2013 https://apod.nasa.gov/apod/ap131120.html, where it was labelled that the artist's impression is for the system 4U1630-47, which was investigated by CSIRO and ESA.] [In] that discussion the same question about the bright white spot was asked and BDanielMayField gave an answer just like Ann's.

BDanielMayfield wrote:
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.

https://en.wikipedia.org/wiki/Pinch_(plasma_physics) wrote:
<<A pinch is the compression of an electrically conducting filament by magnetic forces. The conductor is usually a plasma, but could also be a solid or liquid metal. Pinches were the first device used by humankind for controlled nuclear fusion. The phenomenon may also be referred to as a Bennett pinch (after Willard Harrison Bennett), electromagnetic pinch, magnetic pinch, pinch effect or plasma pinch. Pinches occur naturally in electrical discharges such as lightning bolts, the aurora, current sheets, and solar flares.>>

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(1) Pinches apply a huge voltage across a tube. This tube is filled with fusion fuel, typically deuterium gas. If the multiplication of the voltage & the charge is higher than the ionization energy of the gas the gas ionizes. (2) Current jumps across this gap. (3) The current makes a magnetic field which is perpendicular to the current. This magnetic field pulls the material together. (4) These atoms can get close enough to fuse.

Ann wrote:What a nice picture! And Ivan Eder is one of my favorite astrophotographers.

I had never seen the shock front of Cygnus X-1 before. How fascinating!

Ann

Ann wrote:

rstevenson wrote: In the artist's illustration above, there is a small white point of light where the material from the blue giant blends into the orange stream orbiting the black hole. Since this is an illustration, it seems rather unlikely that the white spot is a background star. But what could it represent? Does the stellar material reach a density sufficient to make it glow before it is torn apart again by the black hole?

Rob

I'm just guessing, mind you. Could that perhaps be the spot where gas flowing from the blue giant companion hits the swirling accretion disk, so that a lot of energy is produced in that small spot?

Ann

https://en.wikipedia.org/wiki/W50_(nebula) wrote:

[b][color=#008000]Radio image of supernova remnant W50 in green[/color], [color=#FF0000]infrared background in red.[/color] [color=#008000]NRAO/AUI/NSF, K. Golap, M. Goss[/color]; [color=#FF0000]NASA’s Wide Field Survey Explorer (WISE)[/color][/b]

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<<W50 or SNR G039.7-02.0, once referred to as the Manatee Nebula, is a Supernova remnant located in the constellation Aquila, about 18,000 light years away. In its centre lies the micro-quasar SS433, whose jets are distorting the remnant's shell. Most likely W50 and SS 433 are related objects, remnants from a supernova which occurred about 20,000 years ago.>>