Planet X:

​

The status of our Planet X model  of periodic mass extinctions as of Jan. 1, 2016 is discussed in the adjacent paper. The original papers with my colleague John Matese are also cited in the adjacent paper. Two more recent papers that suggest the existence of planets that are closer and less massive than the predicted Planet 9 and  consistent with Planet X are (Matthew J. Holman and Matthew J. Payne 2016 AJ 152, 80) and (K. Volk and R. Malhotra  2017 AJ, Volume 154, Number 2).

​

Nemesis:

 

The current status  of Nemesis (D. Whitmire and A. Jackson Nature 1984, 308, 713; Davis et al. Nature 1984, 308, 715) is discussed in the adjacent paper.  The latter version  in which Nemesis is a low mass M-star is ruled out by the WISE full sky IR survey and earlier optical surveys. In our model Nemesis' mass can be as low as 33 Earth masses. Since Nemesis is expected to be near aphelion at this mid-cycle time it would not have been detected by WISE or any other survey. However, IF the more recently measured 27 Myr extinction period is as regular as found my Melott and Bambach (refs in adjacent paper) then our version of Nemesis would also  be ruled out.

​

Tyche:

​

The evidence for this hypothetical object is based on a statistical overpopulation of Oort Cloud comet aphelia along a great circle in the sky (J. Matese and D. Whitmire 2011, Icarus, 211, 926; J. Matese, P. Whitman and D. Whitmire 1999, Icarus, 141, 354. Most of the mass- distance  parameter space was ruled out by WISE. However, a Jupiter mass object between 26,000 and 35,000 AU would not have been detected by WISE which would have observed a Jupiter mass object only inside 26,000 AU.

​

​

​

​

​

​

​

​

​