arrivederci, pluto!pluto, considered a planet since its discovery in 1930 by the american clyde tombaugh will now effectively be airbrushed out of school and university textbooks.
the International Astronomical Union's (IAU) general assembly has passed a resolution following a week of stormy debate declaring that the eight planets are mercury, earth, venus, mars, jupiter, saturn, uranus and neptune.
to qualify, a celestial body must be in orbit around a star while not itself being a star. it must also be large enough in mass «for its self-gravity to overcome rigid body forces so that it assumes a... nearly round shape, and has cleared the neighbourhood around its orbit».
pluto was automatically disqualified because its oblong orbit overlaps with neptune's.
it will now join a new category of «dwarf planets» (no disrespect intended, surely).