What Will It Take To Blow Up Pluto?

“25 billion of your biggest bombs please. I’ll pay credit, thanks!”

The Pluto debate frustrates me, as you may have noticed. It’s not that I have particularly strong views about whether it should be called a planet or a dwarf planet or a plutoid or pygmy planetoid, it’s that I really don’t care; I actually see Pluto’s “demotion” as exciting progress in the field of Solar System science rather than any derogatory gesture aimed at Pluto. Pluto is still Pluto; it hasn’t been knocked out of orbit, it hasn’t even been “bombed” (unlike our poor old Moon), it’s just being filed under a different category.

A King Amongst Dwarfs

In my opinion, calling Pluto a “planet” was unworkable, especially after a bigger dwarf planet was discovered in 2005 by a team of astronomers led by Dr. Mike Brown. This dwarf planet was named Eris (or 136199 Eris) and at first it seemed like we had gained a tenth planet.

The “ten planets” thing was short lived, however. In recognition that Eris probably represented the beginning of a spate of discoveries of welterweight worlds, the International Astronomical Union (IAU) took a vote in 2006 and decided to redefine what constitutes a planet. Pluto was in the firing line, became a rounding error and was dropped from the planetary club.

But it wasn’t all bad for the little guy. Pluto was designated king of all “plutoids” (trans-Neptunian dwarf planets) in 2008, meaning another three dwarf planets now orbited the Sun with this designation (Eris, Haumea, and Makemake in addition to Pluto).

In a previous Astroengine article, I made the point (and I’m going to quote myself because I can):

Just so my opinion is known, I don’t care what Pluto is called. If NASA decided to explode Pluto as part of a Kuiper belt clearing project, then yes, I might be a bit annoyed; I’d even start a blog titled “Save Pluto.” But calling Pluto a dwarf planet (or the rather cute plutino) really doesn’t bother me.

I haven’t really thought much about this statement until, today, @PlutoKiller himself (Mike Brown) tweeted, “Seriously, what just happened? The entire discussion is on placing explosives in the solar system. Pluto has not even been mentioned.” I then fired off a reply saying something about building a New Horizons 2 and packing it with plutonium to which @PlutoKiller said, Evil Santa-style: “Just in time for Xmas.”

And then the penny dropped.

Kuiper Belt Cruelness

To be honest, I’m astonished I haven’t thought of this before. Looking at Mike’s Twitter feed should have been enough inspiration, but until I wondered down the bombing Pluto => plutonium enrichment => lets fly a shedload of plutonium to Pluto path, that I asked the question: How much energy is needed to completely destroy Pluto?

Now we’re talking! Time for some Kuiper belt mayhem!

I’m not talking about simply bombing Pluto and making a big crater, I’m not even talking about fire bombing all the volatiles out of its frozen surface, I want to remove Pluto from existence. Why do I want to do this? Well, for fun, and because @PlutoKiller himself said so. And it’s Halloween, so why not?

So how much energy is required to do this?

For this gargantuan task, I cheated and looked up the method used by Matt Springer over at Built on Facts to derive how much energy was required by the Star Wars Death Star to shred Earth. In that case, 2.2 × 10³² Joules was needed to totally erase our planet (that’s a week’s-worth of solar output). That’s a lot, right?

Plutoid Killing Equation

Now, energy is energy and mass is mass, let’s give Pluto the same treatment. Using the following equation (known henceforth as the “Plutoid Killing Equation”, or simply PluKE), we can find out how much energy we need to erase Pluto:

This equation is the total gravitational binding energy of a sphere of mass, M and radius, R. G is the Gravitational Constant. For Pluto, a sphere, its vital statistics are:

M_Pluto = 1.305 × 10²² kg

R_Pluto = 1.153 × 10⁶ m

and

G = 6.673 × 10^-11 m³ kg^-1 s^-2

Plugging the numbers into PluKE, we can derive the total energy required to kill Pluto, literally:

E_Pluto(dead) = 5.914×10²⁷ Joules

But what does this number mean? This is the bare minimum energy required to match the gravitational binding energy of Pluto. If you want to rip the dwarf planet apart (plus pyrotechnics and speeding debris), you’ll need a lot more energy. However, nearly 6×10²⁷ Joules (that’s a 6 followed by 27 zeros) delivered into Pluto in one second should give the little world a very bad day.

Tsar Very Much

But how can we “deliver” this vast quantity of energy in one second? I suspect that any super-advanced civilization hell-bent of wiping out planets will have a better idea of this than me, but using weapons that are available to modern man might be a good place to start. Forget the uber-powerful death ray emitted by the Death Star, that’s sci-fi. It may not be sci-fact, but how about sending some nuclear bombs to the Kuiper belt?

How many bombs will we need? Ten? Ten dozen? A thousand?

The most powerful nuclear weapon tested was the Soviet 58 MT Tsar Bomba in 1961. So if we know how much energy is released by one of those beasts, we should be able to work out how many we’ll need to send to the unsuspecting Pluto.

1 MT = 1 megaton of TNT = 4.184×10¹⁵ Joules

therefore, a single Tsar Bomba has the potential to release an energy of:

58 MT = 58 × 4.184×10¹⁵ Joules = 2.427×10¹⁷ Joules

We needed 6×10²⁷ Joules to wipe out Pluto, obviously the 2.4×10¹⁷ Joules a single bomb can deliver is woefully short of our goal. So how many Tsar Bomba weapons do we need?

(6×10²⁷ Joules) / (2.4×10¹⁷ Joules) = 2.5×10¹⁰

We need to build 25,000,000,000 nuclear bombs. 25 billion. Ouch.

Obviously, looking at this estimation, it is impossible to destroy a dwarf planet as puny as Pluto using the most powerful weapon known to man. Also, it’s worth keeping in mind that this is the bare minimum of energy that needs to be applied to Pluto to match its gravitational binding energy, so to destroy it, you’ll need a lot more bombs.

There’s also the question of how to distribute the weapons. Would you put them all in one place? Distribute them all around the globe? Perhaps burrow into the centre of the body? I suppose putting all the bombs in one place might be impressive, kicking a chunk of plutoid into space.

Now I must report these findings to @PlutoKiller himself, I fear he won’t be happy with the outcome of my calculations…