Parts of southern Africa and Madagascar enjoyed stunning views of last week’s annular solar eclipse. But the incredible views weren’t just limited to Earth.
NASA’s Solar Dynamics Observatory, or SDO, keeps constant tabs on the sun from its geosynchronous orbit. On September 1st, two more bodies jumped inside the frame – Earth and the moon. You’ll see the Earth briefly block SDO’s view of the sun in the video below. Just as Earth is leaving the frame, SDO spots the moon sliding across the sun’s face.
Cool stuff. You might be wondering why the Earth and moon look different from the SDO. We can see how the Earth’s edge isn’t as well defined as the moon’s. Why is that? Earth’s atmosphere is absorbing different amounts of sunlight at different altitudes, creating a softer edge. The moon’s lack of an atmosphere creates a harder edge.
This isn’t the first time Earth and the moon photobombed SDO at the same time. It happened for the first time last September. During a partial solar eclipse on September 13th, the pair blocked the observatory’s view of the sun again.
An image from the September 2015 eclipse perfectly shows both edges. We can see Earth’s softer edge covering the very top of the sun. And, the moon’s softer edge moving right to left.
NASA’s SDO is used to the Earth and moon getting in the way. Each year, our blue marble barrels through dozens of times. Because of SDO’s orbit, the spacecraft passes behind Earth twice each year. For two to three weeks, the Earth blocks SDO’s view of the sun for at least a few minutes each day.
Today, SDO continues its constant observations of the sun. Every 36 seconds, the observatory collects enough data to fill an entire CD. All of this data will be used to help scientists understand what makes the sun tick.