Dwarf planets, comets, and asteroids are all the rage these days, but we shouldn’t neglect our Solar System’s outer gas planets and their moons. In this new NASA video, 70 days of Neptunian activity was compressed down to 34 seconds — and the effect is pretty damned cool.
The video, which was compiled from 101,580 images (!), is one of the longest continuous clips of an outer solar system object. The observations were taken by NASA’s Kepler spacecraft as part of is new K2 mission.
Neptune makes its appearance at day 15. If you look closely, you can see its moon Triton spinning closely around it. And if you look really carefully, you can spot Neptune’s tiny moon Nereid at day 24. Some streaking asteroids photobomb the video as well.
A NASA release explains Neptune’s strange motion:
Relative orbit speeds explain the interesting motion of Neptune and its moons beginning at day 42. Inner planets like Earth orbit more quickly than outer planets like Neptune. In the movie, Neptune’s apparent motion relative to the stationary stars is mostly due to the circular 372-day orbit of the Kepler spacecraft around the sun. If you look at distant objects and move your head back and forth, you will notice that objects close to you will also appear to move back and forth, relative to objects far away. The same concept is producing the apparent motion of Neptune.
This is also a false-color video; Neptune is actually deep blue, its moons are light grey, and the stars are white. And Neptune is not really moving backwards — it only looks that way because of Kepler’s changing position as it orbits the Sun.