In a week of ridiculously gorgeous astronomy pictures hitting the ‘net, I keep thinking they can’t get cooler… and then this happens: a seriously cool picture of the Sun from NASA’s Solar Dynamics Observatory!

Yegads! [Click to solareclipsenate.]

Given that SDO orbits the Earth and sees the Sun from space, why is the bottom half of the Sun gone in this picture? It’s because we’re seeing a solar eclipse which is actually more like a lunar eclipse except the Moon is not involved.

Hmm, yeah, maybe I’d better explain.

SDO circles the Earth in an inclined orbit*. If the orbit were directly above the Earth’s equator, the Earth would block the Sun once per day, and that’s not so cool for a satellite designed to continuously observe our nearest star! So the orbit was inclined a bit, giving SDO an unobstructed view of the Sun… kinda. The orbit of SDO is inclined to maximize the viewing time for the Sun and to maintain a continuous downlink for its very large data stream (it sends about 15 megabytes of data to Earth every second!). Because of the ...