Here is a comment by Adrian L. Melott. Department of Physics and Astronomy. University of Kansas. Lawrence: (He calls it by it's former name Nemesis)
Sun's Rumored Hidden Companion May Not Exist After All
(He refers to the 27-MY cycle and says in part)
" - If Nemesis existed and had this kind of an orbit, its orbit would not be regular," Melott told SPACE.com. "Calculations indicate its orbit would change by 20 to 50 percent due to the gravitational attraction of stars as they pass by us, and the movement of the sun in the galaxy."
Thus, a celestial body like Nemesis couldn't explain such a long-standing, steady cycle, because its orbit itself would not be steady over such a long period of time.
Melott said his data basically puts the final nail in the coffin of the Nemesis idea. But others aren't so sure. Some in the field question whether the fossil record is really accurate enough to establish a cycle going back that far.
"To that I would say, yes we can, now that the accuracy has improved so much," Melott said. "And even if there were errors in the timing, that wouldn't cause something to appear so clockwork and regular, it would smear the signal out."
Melott and Bambach said it leaves the question of what's causing the extinction cycle totally open.
And I will repeat a snippet from my post #38 above; re your words bolded above:
vis: "But stars are rotating on their own axis, and the orbiting is fixed positions by the galactic influences of location. This s real overview stuff a nd not technical but its essentially the way its set up."
" - In the plane of the galaxy the Sun is located in the small spiral arm we call the Orion arm (or local arm) which is really just connection between the two nearest major spiral arms (the Sagitarius and Perseus arms)... [SNIP] ... We pass through a major spiral arm about every 100 million years, taking about 10 million years to go through . . . "
Curious About Astronomy: How often does the Sun pass through a spiral arm in the Milky Way?
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