APOD #3 on SWAN's ghostly tail

The ion tail in the picture is made up of ionized gas that is energized by the Sun's unltraviolet light. The solar winds sculpt the tail, so that it is always facing away from the Sun. The solar wind is made up of particles that are moved around due to the Sun's magnetic field. The tail of comet SWAN is tinted blue. The blue color appears because atoms are combining into carbon monoxide. The coma of the comet is green, due to the trace amount of cyanogen, which is N#CC#N, being heated by the Sun.

The comet itself unexpectedly brightened last week, which made it a naked-eye magnitude. The comet has passed both the Earth and the Sun, which means soon it will not be able to be seen and will head off into interstellar space.