[0901.4173] A Search for Distant Solar System Bodies in the Region of Sedna.
A study by the discoverer of Eris, Mike Brown, and colleagues, finds that Sedna, the putative inner Oort Cloud object, seems to be rather lonesome out there. There aren’t very many Sednas to be found – less than scores, more like a dozen or so. But the sensitivity to Sedna-sized objects (about 1800 km across) is out to about 100 AU, with larger bodies discernible against background stars out to 1,000 AU. There could be a whole bunch of smaller bodies, but they’re too dim for current scopes. Much further afield and the scope has to stare at the same patch of sky to see objects move for a lot longer than this study did.