Don’t panic; the solar system isn’t falling apart, despite the strange dance on display in this incredible footage captured by NASA’s Solar Dynamics Observatory (SDO).
Sure, the video appears to show the moon crossing the sun’s face and then doubling back, like a celestial yo-yo — but that’s just a matter of perspective. The phenomenon in the video is actually caused by the relative orbits of the spacecraft and the moon around Earth.
You can play a similar visual trick with neighboring cars on a highway: Picture your car speeding up relative to a nearby vehicle, which then appears to move backward. It doesn’t actually reverse, of course; it just can’t keep up with your point of view.
With the spacecraft, this phenomenon is about orbit size instead of speed. The SDO is orbiting much closer to Earth than the moon is. That means that every once in a while, they align just so, with the SDO briefly traveling directly perpendicular to the moon. Then, it turns in its relatively tight orbit around Earth, even as the moon, in its much more distant orbit, continues to swing across the sky.
The video doesn’t show the moon doubling back across the sun, in other words — it actually shows the spacecraft’s perspective doubling back in its own orbit around Earth.
On this particular occasion, the full event took a little over 4 hours on the night of March 6 to unfold. The moon blocks up to 82 percent of the sun’s disk during the crossover.
The SDO has been in geosynchronous orbit since 2010 as it studies the sun in a range of wavelengths.