Kepler Observes Neptune Dance with Its Moons

Seventy days worth of solar system observations from NASA’s Kepler spacecraft, taken during its reinvented “K2“ mission, are highlighted in this sped-up movie. The planet Neptune appears on day 15, followed by its moon Triton, which looks small and faint. Keen-eyed observers can also spot Neptune’s tiny moon Nereid at day 24. Neptune is not moving backward but appears to do so because of the changing position of the Kepler spacecraft as it orbits around the sun. Image credit: NASA Ames/SETI Institute/J.