posted on Dec, 21 2012 @ 03:29 PM
reply to post by BrokenAngelWings33
First off, I think it's really cool that you're using Stellarium to help learn about the sky. I love that program!
Secondly, I'm glad you realize that the software (as a simulation) has its limits.
You have run up against one of these limits. In addition to the location in the sky, Stellarium also includes the stars'
- that is, how far across the sky we see a star move in one year, and in which
direction. Distance is an angle measured in arc seconds (1/3600 of a degree) - the Moon, for example is ~1800 arc seconds (or half a degree) as seen
from Earth. Direction is an angle from celestial north.
One online reference for Rigil Kent lists a proper motion of 3.689 arcsec/yr (281.1° from north). At that rate, in the 5,126 years from -3115 to
2012, Alpha Centauri would move ~5.25 degrees across the sky.
However, it lists this for both component stars (A & B). I think that Stellarium entered the proper motion for A & B separately. I don't have time
to dive into the Hipparcos Catalogue to find these numbers (I'm already late for meeting my family for lunch), but it's safe to assume that they are
different, since the stars orbit each other every 80 years. Stellarium models orbits for objects within our solar system (planets, moons, comets,
etc.), however for objects outside the solar system it just extrapolates stellar positions based on proper motion.
Thus, instead of showing Alpha Centauri A & B orbiting each other, it shows them moving in straight lines across the sky and diverging.
Congratulations - You broke the system!
(Maybe you should ask for your money back. Oh yeah, it's free-ware.)