Neptune and Its Moons

This movie was put together using 70 days worth of solar system observations from the Kepler spacecraft taken during its reinvented “K2” mission. The planet Neptune appears from the left on Day 15, followed by its moon Triton, which looks small and faint. Sharp-eyed observers may also spot Neptune’s tiny moon Nereid at Day 24.

Neptune doesn’t actually move backward in its orbit, but it appears to do so because of the changing position of the Kepler spacecraft as it orbits around the sun. The same sort of retrograde motion is seen in the movement of the outer planets over the course of a year as viewed from Earth.

[youtube https://www.youtube.com/watch?v=Tw-q3uM_5_0]

Video Credit: NASA

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