Of course he’s not a planet !
That shouldn’t be disputable.
That shouldn’t make him any less the beautiful,
That shouldn’t make him any less –
His surface is so mutable,
And not the long-expected pockered granite
Of our Earth-restricted guess –
But plains and ridges run instead,
In shades of red,
Across which canyons slice.
And we were right about the ice,
But not the mountains that it forms !
Mountains that could melt away,
Except he never warms at all –
His crystal peaks that should reflect the sun’s weak glow,
Except they’re covered by the nitrogen that falls as snow.
Dwarf perhaps is too pejorative,
But then, if you’ll forgive, he’s not the same,
And after all, it’s just a name.
There is no magic line
Where we can suddenly define
The class of planets from the dwarfs at just below his size –
To let him cling to planet-hood,
But sorry, Eris, all you other guys are just a might too small.
It’s hardly wise to be so arbit’ry in what should get the planet’s call –
It also shows that gravity is quite misunderstood:
For lack of mass is why he swings
In tilted rings around the sun,
And why he’s kept at bay by Neptune’s sway,
In the long, long run:
So no, he’s not a planet, he’s a diff’rent kind of thing –
We know because we’ve seen him: he’s the cosmic Kuiper king.