Neptune

Triton is the only satellite of Neptune whose mass could be determined from its gravitational perturbation of Voyager 2's hyperbolic flyby orbit. In addition to having its rotation tidally locked to its orbital revolution around Neptune, Triton's rotation axis is almost aligned (to within 1°) with the perpendicular to Neptune's orbital plane around the Sun. The fact that Triton's orbital plane around Neptune is tilted 23° to Neptune's equatorial plane and the nodes (the intersection points of Triton's orbit with Neptune's equator) process along the equator, making a 360° circuit around it in 688 years, causes the seasons on Triton to be much more complicated than they are on Neptune. A graph of the latitude of the subsolar point-the point directly below the Sun-on Triton from the present to the year 3000 is shown in this figure.

The subsolar point was at about 45° South Latitude at the Voyager 2 encounter, and since then has moved further south toward its farthest south value of 52° South Latitude.

The main discoveries that Voyager 2 made about Triton are the following.