An open letter from Pluto: A compelling geophysical case for planethood

A witty open letter from Pluto questions its 'dwarf planet' tag, reviving debate on planetary definitions and whether science-or simplicity-drove its demotion

(Forwarded by Kumar Abishek)

 

Dear Nasa and International Astronomical Union (or IAU, if you please), It’s Pluto. You now call me a “dwarf planet”, which sounds friendly until you realise it quietly means I am not a planet at all. I’ve had time to get comfortable with that label, but it has never quite fitted the reality of who I am. 

First, a note of thanks to Kaela Polkinghorn. It’s not every small, icy world for which 10-year-olds on Earth write to Nasa, asking for their planet status to be restored. 

Also, thank you, Jared Isaacman, Nasa Administrator, for not ignoring the letter, and replying: “Kaela — We are looking into this.” 

This suggests my story may not be entirely settled yet. 

So here I am, adding a gentle reminder from near the edge of the solar system. 

The change, as you know, came with the IAU 2006 Prague vote, when you introduced three rules for planethood, which sound more like zoning laws of a municipal area, because it formally only applies to our solar system, and not other star systems.

Still, I meet the first two easily: I orbit the Sun, and I am in hydrostatic equilibrium, or simply round, shaped long ago by my own gravity.

 

The third rule is where everything shifts: A planet must clear its neighbourhood. 

But out here in the Kuiper Belt, nothing clears its neighbourhood. We coexist, sharing space and moving in steady, predictable paths over extremely long periods. 

The third criterion doesn’t describe what a world is. Move Earth out to my patch beyond Neptune, and it would not clear

its orbit either. Then if you go by the current logic, will you, Earthlings, watch it lose its planetary status among the crowd of Kuiper Belt objects? 

When you look at me closely, the case becomes harder to dismiss. When the interplanetary space probe New Horizons flew by in 2015, it found a world that was active and rich in detail: There are nitrogen glaciers moving across Sputnik Planitia, mountains rising from water ice, and a faint blue atmosphere above. There are even strong hints of an ocean beneath the surface, quietly shaping what you see from afar. 

These are not the traits of something “dwarf”; they are the signs of a world. 

Yet, based on your current definition, those features matter less than whether I have cleared my surroundings. It is a curious way to decide what counts as a planet. 

And, because of this confusion, lessons in classrooms changed. For years, children learned the planets through the sentence: “My Very Educated Mother Just Served Us Nine Pizzas (in some places, it was remembered as, “My Very Educated Mother Just Said Us Nine Planets).” 

After 2006, that changed: The mother was not serving nine pizzas but nachos. I, the ninth planet, was removed, and became an afterthought. 

The term “dwarf planet” adds to that unease: It sounds like a subset, but functions as a boundary. A dwarf star is still a star, and a dwarf galaxy is still a galaxy, but I am placed outside the very category I resemble.

I understand the hesitation. 

If I return, then objects like Eris, Haumea, and Makemake may follow. 

That would make the list longer but it would be a truer representation of the solar system, which is not especially tidy. And it does not need to be simplified to remain understandable. Furthermore, it is also worth recalling that this decision came from a relatively small vote, and has been debated ever since. 

What endured was not the reasoning, but the simpler story that Pluto was demoted. 

If you are looking into this again, then, perhaps, it is time to begin with what a planet actually is. 

If planets are, as many of your own geophysicists argue, bodies shaped by their own gravity and expressing internal processes,

then by that measure, I am not an exception. 

I have weather and seasons (eccentric, admittedly, driven by a 248-Earth year orbit, extreme 119.5-degree axial tilt, and a highly elliptical path), and a complex surface that renews itself. I even come with a companion, Charon — so large that we orbit a shared barycentre. In other words, a shared centre of gravity. 

If anything, I’ve been overachieving. 

Nasa, you have seen me up close and know the kind of place I am. 

IAU, your definitions guide how people understand the cosmos, but they can evolve as understanding deepens. 

And Kaela, your letter has brought this conversation back into focus. So, thank you again. 

Yours, still orbiting quietly, still changing, and still very much a world,

Pluto

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