North & South Star: Polaris & Sirius

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Discussion Overview

The discussion centers around the future roles of Polaris and Sirius as the North and South Stars, respectively. It explores the concepts of precession, proper motion, and the long-term changes in the positions of these stars over thousands of years.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • Some participants note that Polaris is currently the North Star but will not always hold that title, with Thuban and Vega expected to take its place over a 26,000-year cycle.
  • There is mention of the proper motion of Polaris and its gradual change in position relative to the North Celestial Pole.
  • Participants discuss the Southern Celestial Pole, noting that it currently lacks a bright star but that Sirius will eventually serve as the South Star.
  • Questions arise regarding whether the simulations shared include precession and proper motion, with confirmations that they do.
  • One participant inquires about the nature of Sirius' proper motion, questioning if it is abnormally large or primarily due to parallax effects.
  • Another participant highlights the contrast between the relative stability of Polaris and the movement of Sirius over time.
  • Participants express enthusiasm about the visualizations of proper motions in the simulations.

Areas of Agreement / Disagreement

Participants generally agree on the long-term changes in the roles of Polaris and Sirius, but there are questions and uncertainties regarding the specifics of proper motion and parallax, indicating that the discussion remains unresolved in those areas.

Contextual Notes

Some assumptions about the definitions of proper motion and parallax may not be fully articulated, and the discussion does not resolve the implications of these factors on the future positions of the stars.

tony873004
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Polaris won't always be the North Star. Year by year, it is currently getting closer to the North Celestial Pole. So for our lifetimes and the lifetimes of our children, Polaris will be the North Star. But things start to change for our great-great grandchildren. Over a 26,000 year period, Thuban and Vegas will assume the role as the North Star before Polaris resumes its role. Next time around, Polaris won't be quite as close to the pole as it is now due to proper motion. 26,000 years ago, Polaris was even closer to the pole than it is now.

The Southern Celestial Pole currently has no resident bright star. That too will change. Sirius, the sky's brightest star (besides the Sun), is drifting South and will take a few turns serving as the South Star.
North Celestial Pole:
South Celestial Pole:

https://twitter.com/tony873004/status/721165196035620865
https://twitter.com/tony873004/status/721791747462836224

Movies made using http://orbitsimulator.com/gravitySimulatorCloud/properMotionHome.html
 
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Astronomy news on Phys.org
Thanks for sharing. The simulations are very interesting.
 
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Does this simulation include precession?
 
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DrSteve said:
Does this simulation include precession?
Yes. And it includes proper motion as well.
 
tony873004 said:
Yes. Precession is

Yes. And it includes proper motion as well.
Sorry, that was obvious. It's amazing that Sirius will serendipitously become the Southern Star multiple times. Is the proper motion of Sirius abnormally large, or is it large due to mainly to parallax.
 
DrSteve said:
Sorry, that was obvious. It's amazing that Sirius will serendipitously become the Southern Star multiple times. Is the proper motion of Sirius abnormally large, or is it large due to mainly to parallax.
Lol, you quoted my message before I fixed the typo.

Both. It's very close!

Polaris almost sits still, and as a result, it is the pole star every time the north pole points that direction.

Sirius is on the move. Several 26,000 year periods pass between Sirius' first "term of office" and its second.
 
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That was awesome!
I've never seen the proper motions plotted like that.
It looks like an airport out there. :biggrin:
 
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