The relative speeds and positions of the Moon, the Sun and NASA’s Solar Dynamics Observatory resulted in this unusual lunar transit where the Moon appears to pause and reverse course. Credit: NASA / Goddard / SDO
On the evening of March 6, 201
9, the Moon started to transit the Sun, then doubled back and retraced its steps in the other direction — at least, what looked like from the perspective of NASA’s Solar Dynamics Observatory, or SDO, in orbit around Earth.
SDO is regularly seen transit when the Moon passes in front of its view of the Sun. The Moon’s unusual behavior during this particular transit is similar to retrograde motion: When a celestial object appears to move backwards, different points move into their orbits. In this case, the first part of the transit — when the Moon moves left to right — appears to be reverse motion. SDO takes over the Moon, moving at about 1.9 miles per second perpendicular to the Sun-Earth line compared to the Moon’s 0.6 miles per second, making the Moon appear to move in the opposite direction you would see if you were standing still on Earth. 19659005] The second part of the transit – when the Moon appears to pause and rewind – happens as SDO enters the part of its orbit and starts moving away from the Moon, almost parallel to the shadow’s casting through space. At that point, the Moon once again moves faster than SDO — when compared to the Sun-Earth line — it takes over. So the spacecraft now sees it move in the other direction – NASA’s Solar Dynamics Observatory catches lunar freeze frame “/>