Pluto vs Neptune: Mortal Kombat or RomCom? / by Nathalie Ouellette

 In Theaters All The Time (but also never IRL....). Image credit: N. Ouellette.

In Theaters All The Time (but also never IRL....). Image credit: N. Ouellette.

Lots of people ask me what happened to Pluto. Is it still a planet? Does it even exist at all anymore? Is it a part of a massive Illuminati conspiracy meant to enslave us all? Well, in a
nutshell, Pluto still does exist, it’s been downgraded to a “dwarf planet” and the goat lord Baphomet forbids me to speak of our dark secrets. But that’s not the point of today’s post. I was recently asked about Pluto possibly colliding with the planet Neptune and the ensuing mayhem it might cause.

 A sideview of Pluto's orbit (in red) shown to be highly inclined compared to the plane of the Solar System.  Animation credit:  Lookangmany .

A sideview of Pluto's orbit (in red) shown to be highly inclined compared to the plane of the Solar System.  Animation credit: Lookangmany.

It’s a little known fact that Pluto’s orbit actually brings it closer to the Sun than Neptune at certain points due to its high eccentricity. The last time this happened was between February 7th 1979 and February 11th 1999. So wouldn’t this mean that the orbits of Pluto and

Neptune cross twice every cycle? Surprisingly, no! When Pluto’s orbit comes closest to the Sun and to Neptune’s orbit, it is also at its farthest point above Neptune’s path, which means the two planets always steer far clear of each other. The distance between the two at closest approach is 17 AU (the unit measuring one Earth-Sun distance). Pluto actually comes closer to Uranus at times, the shortest distance between the two being 11 AU!

 A view of Pluto's orbit (in red) from above, compared with Neptune's (blue planet). Animation credit:  Lookangmany .

A view of Pluto's orbit (in red) from above, compared with Neptune's (blue planet). Animation credit: Lookangmany.

Now, it is true that Pluto’s orbit is a little chaotic. Pluto is a very small body surrounded by lots of other objects, some of which are gas giant planets! So it is being pulled around quite a bit. One could argue that long term changes in Pluto’s orbit might one day bring it on a collision course with Neptune. Luckily, Pluto and Neptune are caught in a very precise 2:3 resonance with each other. This means that for every 2 full cycles Pluto goes through, Neptune will go through precisely 3 cycles. This is a very stable relationship between the two. If Pluto’s orbit were to change slightly in the future, so too would Neptune’s in order to respect the resonance.

So the moral of this story is Pluto and Neptune are in a very healthy relationship in which they each respect the other’s space. We should all strive to be more like Pluto and Neptune.