NASA's Solar Dynamics Observatory was just sitting around in orbit doing its job, capturing images of the sun. It had a clean line-of-sight until that prankster Earth and its sidekick the moon got in the way.
This all happened on September 13, a day of a partial solar eclipse that was visible from South Africa, Antarctica and the southern Indian Ocean on our Blue Marble.
The Solar Dynamics Observatory is accustomed to seeing the occasional Earth or moon-caused eclipse, but Sunday was special due to the two of them transiting the sun in tandem. "Though SDO sees dozens of Earth eclipses and several lunar transits each year, this is the first time ever that the two have coincided," NASA notes.
NASA published a video of the "double photobomb" on September 14 showing the moon coming into the frame and then Earth arriving to block the observatory's view of the sun completely. When the Earth finally gets out of the way, it is just in time for the SDO to see the tail end of the moon heading out of the picture.
The Earth's atmosphere makes its edges look fuzzy compared to the moon's sharply defined circle.
The Solar Dynamics Observatory launched in 2010 on a mission to study solar activity to help scientists better understand how changes on the sun impact Earth. It is in an orbit that allows it to have a mostly uninterrupted view of the sun. It just so happens that Sunday was the most spectacular interruption in its history.