Quote:
Originally Posted by Astrophe
OK, but if it were a very small star....like a brown dwarf...could it not be possible that it has remained undetected for all of this time and if its orbit is highly elliptical and it approaches its partner star (our Sun) once in every 26,000 years (a time span which has been suggested on a number of websites I've seen), then its presence would be unknown to humanity, because 26K years ago, we weren't really into astronomy ....well nothing that has come down to us, anyway.
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Still no.
A brown dwarf, though dim in visible frequencies, would shine like a lighthouse in the infra red at that distance.
The issue with objects with very elliptical orbits, is that it doesn't take much perturbation to turn then hyperbolic, and out of the solar system they go.
Bear in mind that not only do the orbits of planets/asteroids/comets vary over long time periods, so do the nearest starts.
We are talking incredibly tiny perturbations here, but on a billion year time scale, it's enough to fling objects out.
Various models of the solar system show proto planets being ejected from the solar system.