Seeing in STEREO

This still image from the video shows comet ISON just passing the plane of Mercury, with Comet Encke ahead and slightly above on Nov. 22, 2013. The sun is off-screen to the right.

NASA's Solar Terrestrial Relations Observatory, or STEREO, is monitoring Comet ISON as it approaches the sun. The latest movie from the STEREO-A spacecraft's Heliospheric Imager shows the comet moving in from the left side over a two-day period from Nov. 20 to Nov. 22, 2013. In addition to Earth and Mercury, Comet Encke can also be seen moving through the middle of the view. The sun sits outside the field of view of this camera, located to the right, off-screen, hinted at by the steady stream of particles, called the solar wind, moving in from the right.