saga: Comet Machholz, photographed by STEREO A, 3rd April 2007.
14 images taken with the SECCHI H1 camera over about 15 hours. The Sun is out of frame beyond upper right. Notice that 96P/Machholz has two tails: The longer, straighter gas tail points almost directly away from the Sun, while the shorter, broader dust tail (to the right) is smeared along the comet’s orbital track.
The Solar TErrestrial RElations Observatory (I know, right) is composed of two spacecraft in slightly different heliocentric orbits: STEREO A (for “ahead”) orbits the Sun slightly inside Earth’s orbit, once every 347 days, while STEREO B (“behind”) is slightly outside, orbiting the Sun in 387 days. The difference in orbital speed makes the spacecraft move relative to each other, providing a shifting stereo perspective of the Sun and stars.