Well, I just looked at a table of asteroids, and it appears a few of the bigger asteroids would probably beat Pluto in the gravitational-influence metric (assuming mass is proportional to R^3). If one defined "planetishness" to be the cube of the radius divided by the distance to the orbited star, Ceres would yield a value of 1.01E+8 km^3/AU^2; Pluto would yield only 8.75E+6 km^3/AU^2. Vesta yields 2.24E+7 km^3/AU^2 and Pallas 1.85E+7 km^3/AU^2. I would guess Pluto is third after those two. So we just need to blow up those who rocks and then Pluto can be a planet again. Seriously, though, I would think such a metric might be a good way of defining planets, since it represents something which can be measured for distant planets even if we can't see them. Just have to accept that Pluto's an oddball.
Seriously, though, I would think such a metric might be a good way of defining planets, since it represents something which can be measured for distant planets even if we can't see them. Just have to accept that Pluto's an oddball.Thanks, great reply. Out of curiousity, what number does Mercury give you, compared with, say, Neptune? To do the whole broken record thing, the number needed to make a planet would have to be arbitrary; Ceres is known to be spherical (although that was doubted until recently); not sure about Pallas and Vesta, but I think that they qualify as dwarf planets under the IAU "standard".