On the Existence of a Distant Solar Companion and its Possible Effects on the Oort Cloud and the Observed Comet Population
We analyze the possible existence and detection of a distant massive solar companion. Such an object—if it exists—should be very faint in the visible, so its direct detection might depend on current or future infrared sky surveys, like WISE. Alternatively, its presence could be uncovered through its perturbing effects on nearby objects such as, for instance, Oort Cloud comets (OCCs). We then estimate how putative solar companions of different masses and semimajor axes can perturb nearby OCCs causing an enhancement of the comet flux along the companion's path. We find that a companion of 5 Jupiter masses (MJ ) can produce a signature detectable with the current record of observed new comets, provided that the Oort Cloud contains a dense inner core of comets and that the distance of the perturber is smaller than ~2 × 104 AU. A 1 MJ perturber can produce a signature detectable in the current record only if its distance were smaller than ~(2-3) × 103 AU. The sample of discovered new comets is found to be two orders of magnitude too small to show a signature caused by a Neptune-mass companion at any distance above ~103 AU to a significant level. We also estimate that the Oort Cloud will withstand the steady perturbing effects by a massive solar companion over the solar system age, with only a minor erosion, unless the companion had a mass gsima few MJ , and were at a distance lsima few 103 AU.