What's the largest body in the solar system that you could destroy without endangering humanity?

Question

You're an alien that really likes pyrotechnics. Nothing that goes boom on your home planet (in a safe and responsible manner) satisfies you any more. Why not blow up a planet and see what that's like? However, you're not allowed to do that in your home solar system. The next closest one is ours. Oh, but there are humans on Earth; they can't stop you, but you don't want to hurt them either. You're a bit crazy, but you're not a sociopath. You just wanna see the biggest planetary fireworks show possible.

In short, which is the most massive celestial body in our solar system that you could destroy without endangering human life on Earth, subject to the following constraints?

• You don't want to harm humans, so you definitely can't destroy the Earth, Moon, or Sun.
• It's okay if there is collateral damage, as long as that damage does not include human life (directly or indirectly).
  • This implies that human artifacts (like the Curiosity rover on Mars) on other bodies can be destroyed, even if they're in active use.
• This is in the present day, so the only people off the planet are in orbit (like on the ISS). You don't want to hurt them either.
• It's okay if you're detected before, during, or after the show. You're not interested in stealth.
  • This implies that there may be mass panic on Earth. That's not your problem, though.
• You don't want to stick around or communicate with humanity. Get in, explode, and get out.
  • They might try to contact you, but you just ignore them.
  • You won't be around long enough for them to be able to attack you.
• You don't want humans to have to accommodate your little stunt (e.g. humanity shouldn't have to move underground for a few months).
• You do not have any way to prevent collateral damage except by careful planning. Better pick your target carefully.

The method that you use to actually destroy the body isn't relevant as long as it meets the following conditions:

• You can pick with surgical precision which planetary body to destroy (i.e. you can pick Saturn but spare its moons).
• You have fine control over how much energy is used. So you can avoid introducing excess energy (thus releasing massive heat or radiation).

Answer 1

Ganymede

No matter which one you go for, blowing up a planet is going to make a lot of shrapnel. An asteroid of several miles long is an extinction-level event, and you've just thrown millions of such asteroids, along with billions of smaller meteors, all over the Solar System, and mass tends to fall towards gravity wells. Chances are, enough of those are going to hit the Earth to give humanity a bad day.

If you want to blow something up, your best bet is to aim for an object that is already mostly constrained to a gravity well, minimizing the shrapnel that you'll be dealing with. Fortunately, the biggest moon in the Solar System is also close to the second-biggest gravity well. If you blow up Ganymede, most of the shrapnel will form a fancy ring around Jupiter instead of peppering the inner planets.

Answer 2

I'd strongly suggest your Alien to blow up Neptune or Uranus (latter would make for a nice joke, too)

Saturn and Jupiter have too many moons. With that many moons, you're creating a fleet of rogue-objects that could potentially start a chain-reaction and murderdeathkill everything on Earth. Also too much risk for your Alien.

So Neptune and Uranus. Neptune: Fewer moons than Uranus, most are smaller, too. Triton might be making trouble, but that should be okay.

Uranus: Funny joke, iirc slightly bigger than Neptune and looks prettier. Blowing pretty things up is funnier, isn't it?

Conclusion: don't blow up Jupiter or Saturn. The others are fine, but as size matters (im going strong with the jokes today), Neptune or Uranus should be your Alien's target.

And most importantly:Do NOT hurt Pluto.

Edited out because scientifically unaccurate (could still be added via hand-waving):

As one can read up on this question, Jupiter does not orbit the sun. Both J and S orbit around their combined center of mass wich rests just outside of the sun. By destroying jupiter, you might disturb the suns orbit and screw everything up. So that's probably too risky for your alien.

Answer 3

The answer is go for the biggest and the best. Blow up Jupiter!

If Jupiter can be destroyed with surgical precision, so we can safely assume its moons will be left intact, then the collateral damage will be minimal. More so, if your pyrotechnic explodomaniac alien waits until Jupiter on the other side of the Sun when the explosion occurs.

Jupiter is approximately half a light hour distant from Earth. Its moons will be mainly in Jupiter orbit. While the Jovian barycentre is dispersing across the solar system, the moons will retain their velocity around the Sun and any additional velocity they effectively acquire due to their orbital velocities around Jupiter. Generally this will mean the moons will either move into higher or lower heliocentric orbits. Essentially they will be half a light hour away from the earth and the centre of the solar system, so the Sun and the Earth are safe.

The OP hasn't specified the precise method for making planets going KA-BOOM!! So it is possible that whatever remains of Jupiter might constitute hazardous materials and fragments for the inner solar system. But this should be considered as quite unlikely because the orbital velocities of Jupiter and its moons indicates that Jovian matter and the moons will remain far from earth.

However, if the aliens are zealous in their regard for human life they enjoy taking pot shots and blowing up any fragments that might be heading towards the Earth. But if their method for precisely demolishing Jupiter is sufficiently precise, then they could be capable of blasting Jupiter away from the Sun. Shoot so it gets blasted out and away. This means there shouldn't be problems for the sky falling in on Earthlings.

Answer 4

There are a number of ways to annihilate a planet to consider, all of which have different effects. In addition, it depends on the interpretation of "not harming humans" both in terms of timescales (within the next year, next millenia, next million years, etc.) and in terms of harm (not killing/injuring immediately, not increasing likelihood of death or injury, etc.).

Blow it up

This leaves large fragments (=asteroids) floating around,some of which are likely to cross the Earth's orbit, with a likelihood of collision. A collision definitely falls under the category of harming humans, but in the short term, not something that is likely to happen.

It also removes a gravitational well from that planetary orbit, which had its own effects. In the case of the gas giants (especially Jupiter), they sweep up much of the asteroids and comets that could threaten the inner solar system (and thus us), providing a shield. They also have large numbers of moons whose orbits would change, possibly sending then careering off in random directions, with one or more likely to cross Earth's orbit.

So, if "not harming humans" means "not immediately harming humans", then anything, other than the moon, is possible. (The moon, tidally locked to the earth, performs several vital functions, one of which is keeping the earth steady on its axis. If it were to be removed, earth's rotation would become chaotic (like that of Mars) and our current, predictable seasons would eventually vary wildly.) If it means "not in the next hundred years" then I would add Venus, Mars and the gas giants to that list of no-goes (due to the likelihood of creating a large number of earth-crossing asteroids). If it means "not significantly changing the risk to humanity in the next million years" then probably only Pluto or any of the Kuiper Belt or Oort Cloud objects would be feasible to blow up.

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Reduce it to insignificant pieces

The main effect of this would probably be the loss of gravitational well, but depending on how spread out the particles are, that might not be significant, and they would coalesce back into a (slightly smaller) planet over the period of a few million years.

If the particles are widely spread out, we would have a problem with loss of gravity well.

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Vaporise it (convert to energy).

I'm not sure what the minimum safe distance for watching the mass-conversion of a planet might be, but it is likely to be quite far. Without doing the sums, I would hazard a guess that only the smaller asteroids and anything in the Kuiper Belt or Oort Cloud would be suitable for us to survive the blast of radiation.

It would, however, be very flashy!

The loss of the gravity well would probably not be a problem with those small distant objects.

If we assume that Jupiter was vaporised, and that it produced the same amount of energy as the fusion process in the sun (0.7% mass conversion into energy) it would produce 1.2x10⁴² J. For comparison, the Sun puts out an average of 3.846x10²⁶ W, so if the explosion occurred over 10 seconds, it would be about 3x10¹⁴ times more energetic than the Sun, and outshine the entire galaxy (about 100 billion (=1¹¹ stars). If we assume that Jupiter was on the opposite side of the Sun from the Earth, it would be 968 million km away, and the energy flux would be about 10¹⁶ W/m² at the Earth's distance, lasting 10 seconds.

A similar calculation for Neptune results in an energy flux at the Earth's distance of 4.6x10¹³ W/m².

Now, the Sun is very opaque to radiation (it takes about 4 million years for photons to make their way out of the core), but I don't think it's going to be sufficiently opaque.

By comparison, a Type II supernova puts out about 10⁴⁶ J over a period of about 10 seconds. A Type II supernova occurring 8 parsecs from the Earth might destroy more than half the ozone layer, producing an average flux of 3.05x10¹⁰ W/m² at the Earth, so vaporising Jupiter would produce about 330,00 times more radiation on the Earth than the supernova. Neptune would produce about 1500 times more radiation. I don't think that any of the gas giants would be a good choice to vaporise, even on the opposite side of the sun.

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Convert into a black hole

(EDIT: I've done some very rough calculations, using http://xaonon.dyndns.org/hawking/, and come to a different conclusion than before.)

This would be rather dull, as the planet disappears into a tiny black hole. For example, a Jupiter-mass black hole would be 2.8m in radius, and be barely detectable as its temperature would be barely be above absolute zero. It would evaporate too slowly to notice (well in excess of the lifetime of the universe so far at 1.82x10⁵⁸ years. (I'd previously thought that it would evaporate soon after forming in a flash of gamma rays, but apparently that's only true for really tiny black holes which are also a lot hotter.)

As a result, just about any planetary object can be safely converted into a black hole; either they're too large to noticeably decay, or they're too small to put out the kind of energy that might harm us.

The loss of the gravity well would not be a problem with those objects; the larger ones with a noticeable gravity well would survive for a very long time, and the smaller ones wouldn't have a noticeable gravity well anyway.

Answer 5

While you could certainly blow up Jupiter, being the largest of the bodies in our solar system, I think the biggest factor is distance here, not size. In other words, the riskiest body to blow up is likely Venus due to its relative distance to Earth.

Though the pieces would go in every direction, the amount of space it would have to traverse before it reached Earth would be enormous. As a result, very little, as it turns out, would reach earth, and the pieces which do end up orbiting Earth would burn up in Earth's atmosphere. The truly dangerous pieces would have to have a straight trajectory and would have to be several kilometers in size, something that is not likely to happen statistically.

Most of the debris would simply follow its natural orbit around the sun, and although some would fall back together due to gravity, it would not reform any resemblance of a planet until much much later.

TL;DR - In other words, distance, not size is relevant, and the distances that you'd have to traverse to get to the planets in our solar system mean the really only truly dangerous planet to blow up for the inhabitants of Earth would be Earth itself.

Answer 6

Did you ever hear of the Endor Holocaust? You can find sites on the internet that argue for and against the Endor Holocaust, the theory that the Endor moon would have been devastated by the explosion of the second Death Star.

http://www.businessinsider.com/endor-holocaust-star-wars-science-physics-2015-121

And what about the Yavin IV holcaust? What happened to the habitable and partly jungle covered fourth moon of Yavin when the expanding cloud of gas that resulted from the explosion of the first Death Star struck Yavin IV? Could any life survive on Yavin IV? Did the rebels have to rapidly evacuate Yavin IV before the shock wave from the Death Star struck the moon?

And what about the deadly radiation emitted by the explosions? Would everyone and all life forms on the near sides of Endor's Moon and Yavin IV receive fatal does of radiation or perhaps even be instantly vaporized even at distances of thousands or millions of miles?

The only way to know is to have someone do the calculations and see.

In the meantime I would guess that it might not be safe for Earth and Earth life to blow up even distant Pluto.

So maybe the explosion loving alien should take his super bomb into interstellar space and explode the planet buster in empty space. Thus he can see a very, very, very, very, very big explosion.

If the explosion loving alien needs to see a huge object be destroyed, maybe he can go the Oort Cloud in our solar system (his fellow aliens would prefer he does it in our solar system instead of theirs). The Oort cloud can be considered to both be in interstellar space and in the outer reaches of our solar system.

The Oort cloud is believed to consist of an inner torus shaped cloud of comets stretching from 2,000 to 20,000 Astronomical Units (AU) from the Sun and an outer spherical cloud that stretches from about 20,000 AU (0.32 light year) to about 50,000 AU (0.79 light year) or possibly several times that distance from the Sun.

It is believed that the billions and trillions of comets in the outer Oort cloud may have a total mass of about 5 earth masses. It is believed that the inner Oort cloud contains tens or hundreds of times as many comets as the outer Oort cloud.

So the bang loving alien can spend centuries, or millions of years, or however long it takes, to change the orbits of trillions of comets in the Oort could and assemble them into a planet large enough to satisfy his lust for explosions and then blast it with his planet busting bomb.

And maybe that will be far enough from Earth that the radiation does not kill any Earth life. And maybe that will be far enough from Earth that the expanding sphere of gases will not destroy all life on Earth. And maybe that will be far enough from Earth that the expanding sphere of debris will not be thick enough when it reaches Earth to cause any extinction level impacts.

Or maybe the alien will build not one planet but two planets that orbit each other. And when the planets are lined up with the inner solar system he will explode the planet that is farther away from the Sun. And the planet closer to the Sun might shield the solar system, absorbing radiation and shock waves and debris and creating a safe shadow that covers the planets of the solar system.

Or maybe the alien will plant his bomb in the Sun, at one of the poles pointing perpendicular to the plane the planets orbit in. And his giant explosion might blast away a chunk of the sun the size of a planet and send it on its way out into interstellar space. But the planet sized chunk of material ejected from the Sun will be only a tiny insignificant fraction of the Sun's mass and the Sun will continue basically unchanged - we hope.

It is certainly possible to create a very, very, very, big explosion on the Sun that would be very spectacular at close range (but far enough away to be safe, of course) but not be noticed at the distance of Earth.

In any case the only safe solar system planet to blow up might have to be an artificial planet as far out in the Oort could as possible.

Answer 7

Well if u blow up any planet it will destroy the whole solar system as taking up Neptune. Neptune will be destroy than its explosion will effect Uranus due to this Uranus will also be come to an end then comes Saturn my favourite planet but if Saturn will be dead it will be disasterous explosion as it has so many moons it's rings then Jupiter it's destruction is very much dangerous as it has bigger mass much explosion material harmful gases and it will effect asteroid belt if that disturbs the earth will come back where it was started from...... 💥