# First observation that the movement of a planet or asteroid in its orbit was affected by another planet?

Answers to the question How did Kepler determine the orbital period of Mars? describing careful observations centuries ago got me thinking.

Question: What was the first analysis of observations that directly demonstrated that the movement of a planet or asteroid in its orbit was affected by gravitational attraction by another planet?

I don't mean inferences based on the spacing of orbits, I'm thinking of detailed positional measurements; something like planet/asteroid A was X kilometers or Y arcseconds away from it's predicted position and it couldn't be accounted for if not for the gravitational effects of planet B.

I am not sure if First observation that the Sun and Jupiter (and friends) move around a common barycenter? is a completely separate question, or if this confirmation happened all at once, but I've currently asked it separately.

• To what I know I think there were two of these, but idk which came first: 1) Uranus was affected by something. Then two scientists in separate countries mathematically calculated its position. 2)The same astronomer that mathematically calculated Neptune first proposed another possible planet Vulcan, and mathematical calculated its orbit[inside Mercury's, affecting Mercury's orbit]. – Max0815 Feb 25 '19 at 4:26
• @Max0815 They should be correct. I'll edit: "directly demonstrated" → "directly and correctly demonstrated" – uhoh Feb 25 '19 at 4:39
• We can determine the masses of planets if they have moons. For Mercury and Venus (pre space age) we had to deduce their masses from perturbations by other planets. I guess this would be among the earliest studies of this phenomenon. See:Determination of planetary mass and radius., Determination of Masses of Mercury and Venus from Observations of Five Minor Planets. – Keith McClary Feb 28 '19 at 4:45
• @KeithMcClary Great! Then I think that citing the first mass deduction of Mercury and/or Venus (or even possibly of Earth) based on perturbations by other planets would be an excellent answer to my question! – uhoh Feb 28 '19 at 4:55
• It seems to be a complicated tale: google.ca/search?q=Leverrier+mass+venus , gsjournal.net/Science-Journal/… Someone on hsm.SE might know this. – Keith McClary Feb 28 '19 at 5:28