On 11-02-18 06:20 PM, Dr J R Stockton wrote:
With an assumed mass of 4 Jupiters, such a planet would be very easy to
detect given 19th century (or earlier) technology and sufficient
patience. It will displace the barycentre of the solar system
periodically by of the order of 250 AU, and Sun and Earth both orbit
that barycentre. That will easily be detected by parallax measurements
of many of the nearer stars, assumed to be on the average fixed.
Unfortunately, the orbital period is of the order of 1.8 M years.


Even with 4 Jupiter masses, the Sun still outweighs it by 250 times, so
the barycenter still lies much closer to the Sun than this planet.

Yousuf Khan