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Solar Dynamics Observatory catches lunar freeze frame

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 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 “/>

NASA’s Solar Dynamics Observatory spotted a lunar transit just as it began the transition to the dusk phase of its orbit, leading to the Moon’s apparent pause and change of direction during the transit. This animation (with orbits to scale) describes the movement of the Moon, its shadow and SDO. Credit: NASA / SDO

This is not the first time that SDO has seen the Moon seem to move in two different directions during a lunar transit. This time, the Moon just happened to be in SDO’s sight as it started the dusk part of its orbit, leading to the freeze-frame effect.

This lunar transit lasted about four hours, from 5 p.m. to 9:07 pm EST, and at peak, the Moon covered 82 percent of the Sun’s face. The Moon’s edge appears sharp because the Moon has no atmosphere. On the other hand, Earth eclipses of the Sun have a blurry edge when seen by SDO, because the gases in Earth’s atmosphere let through only part of the Sun’s light.


Explore further:
SDO spots two lunar transits in space

Provided by:
NASA’s Goddard Space Flight Center


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