For 10 points, identify this event which resulted in the identification of the planet perturbing the orbit of Uranus.
One person who participated in this event wrote a letter to James Challis requesting an investigation Another letter by an individual participating in this event was sent to Johann Galle, who also participated in this event with the help of his student Heinrich D'Arrest. Galle and D'Arrest carried out the observation crucial to this event, an observation also attempted by Challis at the behest of George Airy. This event was prompted by the discovery of perturbations in the orbit of a certain (*) planet, which resulted in two independent attempts to predict the location of another body on the basis of calculations carried out by John Couch Adams and Urban Le Verrier. For 10 points, identify this event which resulted in the identification of the planet perturbing the orbit of Uranus.
One person who participated in this event wrote a letter to James Challis requesting an investigation Another letter by an individual participating in this event was sent to Johann Galle, who also participated in this event with the help of his student Heinrich D'Arrest.
discovery of Neptune [accept equivalents which indicate that Neptune was found for the first time]