Enlarge / Just one of … 110 planets in the Solar System? (credit: NASA/JHUAPL/SwRI)

It’s no secret that Alan Stern and other scientists who led the New Horizons mission were extremely displeased by Pluto’s demotion from planet status in 2006 during a general assembly of the International Astronomical Union. They felt the IAU decision undermined the scientific and public value of their dramatic flyby mission to the former ninth planet of the Solar System.

But now the positively peeved Pluto people have a plan. Stern and several colleagues have proposed a new definition for planethood, which they intend to submit for consideration at the next general assembly of the IAU. The final arbiters of astronomical definitions will next gather in Vienna in August 2018.

In technical terms, the proposal redefines planethood by saying, “A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.” More simply, the definition can be stated as, “round objects in space that are smaller than stars.”