The definition of a planet is being decided right now at a conference of the International Astrophysical Union in Prague. At stake is not only the planethood of Pluto, but potentially even the mooniness of the earth’s moon.

The first definition, proposed last week, says every round object orbiting the Sun is a planet, unless it orbits another planet; but, even an object orbiting a planet may also be a planet if the center of gravity of the system is outside the larger object. That would increase the number of planets in the solar system from 9 to 12, including Pluto’s moon Charon. Eventually, some billions of years from now, when the Earth’s moon has drifted farther away from the Earth, it too would become a planet. It also opens the door to the possibility of hundreds of new “planets” being found as astronomers discover more distant objects out near the Kuiper belt.

After some debate, a second definition has been introduced, building on the first definition but adding the stipulation that “a planet is a celestial body that is by far the largest object in its local population.” This addition would eliminate both Pluto’s moon and Pluto itself from planet classification, reducing the number of planets in the solar system to eight and wreaking havok in preschools across the globe as teachers have to come up with explanation for what happened to Pluto.

Another item of contention up for debate at the IAU conference: if they’re not planets, then should Pluto-type objects be called plutons or dwarf planets?

If you’re wondering how the world’s astronomers decide these things, it’s not with a coin toss or an eye-poking contest, but rather with an upcoming vote on Thursday, Aug. 24.