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The density wave should explain the spiral galaxy structure.
However, in the following article it is stated clearly that it can last for maximal ten rotation periods:
So, how could it be that the Milky Way last for so long time?
Our scientists claim that it takes 240MY for the sun to set one rotation.
In the last 6 BY it had been set about 25 rotation periods.
Hence, how the Milky Way could last for 25 rotation periods
Let me give you a fair bit of warning, Dave: keep your "Theory D" out of this. If you start talking about it, I'll close this thread for the exact same reason I closed your other thread about Theory D.
However, is it ok with you that I ask few questions?
OK, so the wave might not persist for too long at a time, probably less than a billion years at a time.
Various models should give rise to a statistical prediction of galaxies that have not had recent significant collisions
How could it be that 72 present of the galaxies that we observe are spiral while based on the Density Wave statistical theory each one of them could keep its spiral structure for only a billion years?
Dave, can you check if the issue you raised wasn't already solved by one (or more) of the later theories put forward in the last half a century or so?
"Three leading hypotheses are Density-wave theory (Lin & Shu, 1964), Stochastic Self-Propagating Star Formation (SSPSF) Mueller & Arnett (1976) and the Manifold theory (Athanassoula et al., 2010).
Well, I took your advice and made some homework.
Hence, exactly 64 stars in any 50Ly sphere.How can we explain this absolutely fixed density
72 present of the galaxies that we observe are spiral
In a radius of 100 Ly around us we observe 512 stars. In a radius of 50 LY we observe 64 stars.Hence, exactly 64 stars in any 50Ly sphere.
Quote from: Dave Lev on 04/12/2021 18:44:49In a radius of 100 Ly around us we observe 512 stars. In a radius of 50 LY we observe 64 stars.Hence, exactly 64 stars in any 50Ly sphere.Would you like to rephrase that? You clearly did not literally mean the bolded part.
https://en.wikipedia.org/wiki/Stellar_density"The true stellar density near the Sun is estimated as 0.004 stars per cubic light year, or 0.14 stars pc−3"Given a volume of radius 50 LY, (~14175 pc³) this works out to very close to 2000 stars within that radius of us, hardly 64. I've brought up this point before, but Dave is still asserting things from prior threads.
Of those 64, are 32 in the Northern and 32 in the southern sky?Because, if they aren't the density isn't fixed and the obvious "explanation" is just coincidence.
QuoteQuote from: Dave Lev72 present of the galaxies that we observe are spiralYou seem to imply that these are flat galaxies that don't show a spiral structure.That's because there are many other types of galaxies that aren't flat:- Elliptical galaxies are formed by the collision of two or more galaxies, which disrupts any spiral pattern, and consumes most of the dust (so new arms can't form). This will happen to Milky Way + Andromeda = "Milkomeda"- Dwarf galaxies/irregular galaxies/globular clusters : Their arms have been distorted and ripped off by interactions with a larger galaxy, leaving no record of spiral arms (if any)See: https://en.wikipedia.org/wiki/Galaxy#Types_and_morphology
Quote from: Dave Lev72 present of the galaxies that we observe are spiral
Total Speculation: We now know that most galaxies have a central black hole.- We know that there are relativistic jets produced from the accretion disk around this black hole- Sometimes there are 2 or more central black holes, remnants of previous galactic mergers- We expect that the axis of the central jets will change when central black holes merge (and there are examples of this in radiotelescope images)- So what if a black hole merger produces a jet whose axis intersects the disk of the galaxy?- Won't that set off linear changes in the disk (eg a barred spiral)?Of course, a relativistic jet might not be comfortable for life in the spotlight...Please Discuss...
However, I have got a direct order from Kryptid not to do so.
the old habits of cherry-picking facts and misrepresenting what articles and posters actually say
Of those 64, are 32 in the Northern and 32 in the southern sky?
"As many as 512 or more stars of spectral type "G" (not including white dwarf stellar remnants) are currently believed to be located within 100 light-years or (or 30.7 parsecs) of Sol -- including Sol itself. Only around 64 are located within 50 light-years (ly),"So, I discuss about G stars ((not including white dwarf stellar remnants).
Quote from: Dave Lev on 05/12/2021 04:40:41"As many as 512 or more stars of spectral type "G" (not including white dwarf stellar remnants) are currently believed to be located within 100 light-years or (or 30.7 parsecs) of Sol -- including Sol itself. Only around 64 are located within 50 light-years (ly),"So, I discuss about G stars ((not including white dwarf stellar remnants).That does not address the problem statement.You said this, "Hence, exactly 64 stars in any 50Ly sphere."I think you misspoke since this is clearly not possible, even if we are talking about G type stars. So that quote is not correct, right? This should be a yes or no answer.
Quote from: Bored chemist on Yesterday at 19:16:51Of those 64, are 32 in the Northern and 32 in the southern sky?
For further information, please feel free to call them.
Quote from: Dave Lev on 05/12/2021 16:24:47For further information, please feel free to call them.But "exactly 64 stars in any 50Ly sphere."Is your idea, not theirs, so I'm asking you.Feel free to admit that you can't defend your idea.
Do you confirm that our scientists at Hubble telescope OBSERVE 512 G stars in a radius of 100Ly around us?Hence, do you agree that based on this data by average there should be 64 stars in each 50 Ly sphere?Do you confirm that our scientists OBSERVE for 64 stars in a radius of 50Ly around us?Hence, do you agree that there is perfect correlation between the calculated G star per 50LY sphere ( in that 100 LY sphere) to the measured 50 Ly sphere around us?