A Salty Tail

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Sometimes the line between “planet” and “comet” can get a little blurry…especially in Mercury’s case! This video, taken by NASA’s two-piece STEREO (Solar Terrestrial RElations Observatory) spacecraft – consisting of one unit orbiting the Sun just ahead of the Earth and another behind – shows Mercury over a four-day period, shining brightly in the solar wind and exhibiting a tail of gas streaming away opposite the sun in very much the same manner as a comet’s tail. This tail may be made of sodium atoms stripped off the planet by solar wind, but some researchers at Boston University say that the tail is shining too brightly to be sodium. Whatever the case it’s another example of the discoveries scientists are making every day about our solar system, with the help of amateur astronomy enthusiasts around the world!

Of special interest is the way the tail feature was spotted in the STEREO data. It was not found by the BU team, but by Ian Musgrave, a medical researcher in Australia who has a strong interest in astronomy. Viewing the on-line data base of STEREO images and movies, Dr. Musgrave recognized the tail and sent news of it to Boston asking the BU team to compare it with their observations.

– Boston University Imaging Science press release

Read more about this on Universe Today.

Video credit: Carl Schmidt, Jeffrey Baumgardner, Prof. Joshua Semeter from Boston University.