Starship Asterisk*

Chris Peterson wrote: ↑Sat Aug 29, 2020 2:20 pm
It's not even clear why a pair of black holes in the center of a galaxy would produce an asymmetric structure of stars. The mass of the stars in a galaxy's core hugely outmasses one or two black holes. And the black holes would be orbiting each other, so they wouldn't be maintaining a fixed orientation that you'd probably need to form any structure in the first place. I'd expect the core of a galaxy that contained two black holes to have the same structure that the core of any unbarred galaxy has- spherical.

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

Exaggerated diagram illustrating Lin and Shu's explanation of spiral arms in terms of slightly elliptical orbits.

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<<The first acceptable theory for the spiral structure was devised by C. C. Lin and Frank Shu in 1964, attempting to explain the large-scale structure of spirals in terms of a small-amplitude wave propagating with fixed angular velocity, that revolves around the galaxy at a speed different from that of the galaxy's gas and stars. They suggested that the spiral arms were manifestations of spiral density waves – they assumed that the stars travel in slightly elliptical orbits, and that the orientations of their orbits is correlated i.e. the ellipses vary in their orientation (one to another) in a smooth way with increasing distance from the galactic center. This is illustrated in the diagram to the right. It is clear that the elliptical orbits come close together in certain areas to give the effect of arms. Stars therefore do not remain forever in the position that we now see them in, but pass through the arms as they travel in their orbits.

The density wave theory also explains a number of other observations that have been made about spiral galaxies. For example, "the ordering of H I clouds and dust bands on the inner edges of spiral arms, the existence of young, massive stars and H II regions throughout the arms, and an abundance of old, red stars in the remainder of the disk". When clouds of gas and dust enter into a density wave and are compressed, the rate of star formation increases as some clouds meet the Jeans criterion, and collapse to form new stars. Since star formation does not happen immediately, the stars are slightly behind the density waves. The hot OB stars that are created ionize the gas of the interstellar medium, and form H II regions. These stars have relatively short lifetimes, however, and expire before fully leaving the density wave. The smaller, redder stars do leave the wave, and become distributed throughout the galactic disk.>>

JohnD wrote: ↑Sat Aug 29, 2020 5:44 pm
"Our" own Milky Way, Neufer? Oh, of course, you only vacation at Tralfamodore [sic],
and that's in our very own Magellanic Cloud! 'Our' galaxy, indeed!

• I have dual citizenship for both Titan & Tralfamadore.

https://en.wikipedia.org/wiki/Tralfamadore wrote:
<<In The Sirens of Titan, Tralfamadore is a planet in the Small Magellanic Cloud and the home of a civilization of machines, which dispatches Salo to a distant galaxy with a message for its inhabitants. After a part in his ship breaks, however, Salo is forced to land on Titan, a moon of Saturn, where he befriends Winston Niles Rumfoord. Rumfoord exists in much the same way as the Tralfamadorians of Slaughterhouse-Five, while Salo appears to move in a linear fashion. The translation of Tralfamadore is given by Salo as both all of us and the number 541. The Tralfamadorians were originally developed by super-beings who built them to allow themselves to search for a meaning to their lives. Unable to achieve this task, they eventually asked the machines to do it for them, and upon knowing that they could not be said to have any purpose at all, the precursor race decided to eradicate itself, just to realize that they were not even very good at this, so they used the Tralfamadorians instead to complete the annihilation of their race.>>

JohnD wrote: ↑Sat Aug 29, 2020 5:44 pm
I meant two BHs as cause of a galactic bar, that would, by definition, NOT be at the centre of a galaxy, Chris, but orbiting its centre of mass. Very slowly, as slowly as a galaxy rotates (?). Their interaction would draw matter and stars into that central bar.

Hoyle, Masters, Nichol et al, found that galactic bars were between 3 and 20 kiloparsecs long (10 and 100 ight years), and that of observed galaxies, the higher the red shift (the youngest) the longer the bar. This would correspond with BHs marking the foci of a bar, and their orbits slowly getting smaller with time, presumably due to tidal effects on each other and their surounding matter. https://academic.oup.com/mnras/article/ ... 27/1749219

As the BHs migrated inwards to eventually merge at the centre, the bar would get shorter, but may remain for some time , after the central cataclysm.

https://en.wikipedia.org/wiki/Doppelg%C3%A4nger_(1969_film) wrote:
<<Doppelgänger is a 1969 British science-fiction film. Outside Europe, it was released as Journey to the Far Side of the Sun, the title by which it is now more commonly known. Set in 2069, the film concerns a joint European-NASA mission to investigate a newly-discovered planet that lies opposite Earth on the other side of the Sun. The mission ends in disaster and the death of one of the astronauts, after which his colleague comes to believe that the planet is a mirror image of Earth.>>

JohnD wrote: ↑Sat Aug 29, 2020 5:44 pm "Our" own Milky Way, Neufer? Oh, of course, you only vacation at Tralfamodore, and that's in our very own Magellanic Cloud! 'Our' galaxy, indeed!

I meant two BHs as cause of a galactic bar, that would, by definition, NOT be at the centre of a galaxy, Chris, but orbiting its centre of mass. Very slowly, as slowly as a galaxy rotates (?). Their interaction would draw matter and stars into that central bar.

As the BHs migrated inwards to eventually merge at the centre, the bar would get shorter, but may remain for some time , after the central cataclysm.

JohnD wrote: ↑Sun Aug 30, 2020 11:05 am
Art, I have no doubt in the alternate Earth on the other side of the Sun, but I refer you to Russell's Teapot.

neufer wrote: ↑Sun Aug 30, 2020 12:50 pm

Click to play embedded YouTube video.

BDanielMayfield wrote: ↑Sun Aug 30, 2020 1:14 pm
While JohnD's befuddlement might remain, at least my being drawn into Idaho's ergosphere is fully explained. (Northern Idaho, I want to go to there. Must plan trip. Soon.)

https://en.wikipedia.org/wiki/Copernican_principle wrote:
In physical cosmology, the Copernican principle states that humans, on the Earth or in the Solar System, are not privileged observers of the universe. Named for Copernican heliocentrism, it is a working assumption that arises from a modified cosmological extension of Copernicus's argument of a moving Earth. In some sense, it is equivalent to the mediocrity principle.

JohnD wrote: ↑Sun Aug 30, 2020 11:05 am Excuse me, Chris! My thinking was that we know that binary BHs exits, do orbit each other, and from the LIGO and other observatories do get closer and closer and eventually merge. How likely is it for BHs to come into existence close to each other? Or widely, galactically, seperated, and over time be mutually attracted. You can estimate the timescale better than I can.

But why do you ask those Qs? "Why would a pair of black holes draw stars toward them? Why would they significantly distort a cloud of stars around them that exceeded their own masses by a couple of orders of magnitude?" The answers are obvious: Gravity, and because Supermassive BHs exceed the Sun's mass by millions or billions of times. I assume this is a rhetorical Q, but cannot see the point.

Chris Peterson wrote: ↑Sun Aug 30, 2020 2:33 pm The gravitational influence of a supermassive black hole is not very significant once you are just a few light years away from it.

BDanielMayfield wrote: ↑Sun Aug 30, 2020 8:51 pm Neil deGrasse Tyson recommends that we "question everything", so when

Chris Peterson wrote: ↑Sun Aug 30, 2020 2:33 pm The gravitational influence of a supermassive black hole is not very significant once you are just a few light years away from it.

it makes me wonder. The relative unimportance of supermassive black holes is an opinion Chris has stated in various ways at several times over the years here in this forum. Here at least he makes a claim that can be tested. Stay tuned for the aftermath.

Chris Peterson wrote: ↑Sun Aug 30, 2020 9:13 pm

BDanielMayfield wrote: ↑Sun Aug 30, 2020 8:51 pm Neil deGrasse Tyson recommends that we "question everything", so when

Chris Peterson wrote: ↑Sun Aug 30, 2020 2:33 pm The gravitational influence of a supermassive black hole is not very significant once you are just a few light years away from it.

it makes me wonder. The relative unimportance of supermassive black holes is an opinion Chris has stated in various ways at several times over the years here in this forum. Here at least he makes a claim that can be tested. Stay tuned for the aftermath.

We can't even tell if a galaxy has a supermassive black hole unless it's active. Because it doesn't alter the movement of stars in the core, except for the handful (two so far) of cases where we can use interferometry to actually resolve the inner few parsecs.

BDanielMayfield wrote: ↑Mon Aug 31, 2020 2:45 pm

Chris Peterson wrote: ↑Sun Aug 30, 2020 9:13 pm

BDanielMayfield wrote: ↑Sun Aug 30, 2020 8:51 pm Neil deGrasse Tyson recommends that we "question everything", so whenit makes me wonder. The relative unimportance of supermassive black holes is an opinion Chris has stated in various ways at several times over the years here in this forum. Here at least he makes a claim that can be tested. Stay tuned for the aftermath.

We can't even tell if a galaxy has a supermassive black hole unless it's active. Because it doesn't alter the movement of stars in the core, except for the handful (two so far) of cases where we can use interferometry to actually resolve the inner few parsecs.

That sounds like you might even question the existence of a supermassive black hole at the core of the Milky Way. :shock: Would you care to clarify?