The occultation of the dwarf planet Eris in November 2010

This animation shows the path of a faint star during the occultation of the dwarf planet Eris in November 2010. Two sites in South America saw the faint star briefly disappear as its light was blocked by Eris and another recorded no change in brightness. Studies of where the event was seen, and for how long, have allowed astronomers to measure the size of Eris accurately for the first time. There is only one star, but its path is different relative to Eris at different sites, so three tracks are shown here. Surprisingly, the astronomers found Eris to be almost exactly the same size as Pluto and that it has a very reflective surface.