  I have carried out a search for Planet 9 in the IRAS data. At the distance
range proposed for Planet 9, the signature would be a 60 micron unidentified
IRAS point source with an associated nearby source from the IRAS Reject File of
sources which received only a single hours-confirmed (HCON) detection. The
confirmed source should be detected on the first two HCON passes, but not on
the third, while the single HCON should be detected only on the third HCON. I
have examined the unidentified sources in three IRAS 60micron catalogues: some
can be identified with 2MASS galaxies, Galactic sources or as cirrus. The
remaining unidentified sources have been examined with the IRSA Scanpi tool to
check for the signature missing HCONs, and for association with IRAS Reject
File single HCONs. No matches of interest survive.
  For a lower mass planet (< 5 earth masses) in the distance range 200-400 AU,
we expect a pair or triplet of single HCONs with separations 2-35 arcmin.
Several hundred candidate associations are found and have been examined with
Scanpi. A single candidate for Planet 9 survives which satisfies the
requirements for detected and non-detected HCON passes. A fitted orbit suggest
a distance of 225+-15 AU and a mass of 3-5 earth masses. Dynamical simulations
are needed to explore whether the candidate is consistent with existing planet
ephemerides. If so, a search in an annulus of radius 2.5-4 deg centred on the
1983 position at visible and near infrared wavelengths would be worthwhile.
