http://www.scienceagogo.com/news/20060326012725data_trunc_sys.shtml Strange state of affairs, Sedna should not be there without a companion star to the sun, or its orbit is a relic of when stars were much closer, both seem a bit far fetched, is this the latest information?
This Brown is presumably saying that Sedna is never close enough to have its orbit perturbed directly by the Sun - not that it is outside the Sun's gravitational influence altogether! That would be absurd. If he's implying that its elliptical orbit could not have developed without past gravitational perturbations, isn't it possible this occurred through a series of encounters with other large Scattered Disc objects? There are, almost certainly, a great many of them still undiscovered, possibly larger than Eris (a.k.a. Xena). All the same, the idea of a dark stellar companion to the Sun is not new, and has an undeniable romantic appeal. I'd like to think it might exist. And if it does, it will quite likely have a little planetary system of it own, comparable in scale to the satellite system of Jupiter or Saturn... The planets would be shadowy, frigid places of eerie red twilight and flickering volcanic oases, maybe with Europa-esque frozen oceans or rolling seas of liquid methane. It would be an irresistable target for the next, much faster generation of space probes, and perhaps manned missions within a century or two. Please Register or Log in to view the hidden image!
The linked paper seems to suggest different theories. http://arxiv.org/PS_cache/astro-ph/pdf/0412/0412030v1.pdf None of them suggest a binary companion. I dont know however what thse models are worth.
Oh - and the Wikipedia Sedna article was last updated on 17 May 2007. Doesn't seem to be any more recent reference out there.
Only because nobody could find one. There are thousands of red dwarfs whose distance and absolute magnitude are hard to determine - to say nothing of brown dwarfs, which only became detectable in the last decade or so. A substellar body maybe 2-5% of the Sun's mass, located thousands of AUs away - or even a light year - would be far dimmer than most normal background stars, and only exceptional in its proper motion. [Possibly the only scientifically accurate statement in the movie Armageddon: "It's a big-ass sky!!"] Bsemak: the theories in that paper you linked are as worthwhile as any. If the Sun formed amid a long-dispersed cluster of young stars, relatively close encounters must have happened plenty in its early history.