Maggie A's Meanderings




Addendum for October 16, 2011

Star Wars, Einstein and When Lucas Got It Right Addendum:
Difficulty Levels of Death Star Versus Various Astronomical Bodies

In writing "Star Wars, Einstein and When Lucas Got It Right" I obviously spent some time doing research on the Solar System. It occurred to me that you could get a general sense of how tough one astronomical body would be to blow-up relative to another body by comparing size and density. It wouldn't be perfect because composition matters, but it would give a rough idea.

I had ended up doing a spreadsheet for "Star Wars, Einstein and When Lucas Got It Right," so, on a whim, I decided to plug in an equation using mass, volume and density.

((mx/me)+(vx/ve)+(dx/de))/3 where 
mx=mass of astronomical body
me=mass of Earth
vx=volume of astronomical body
ve=volume of Earth
dx=density of astronomical body
de=density of Earth
The equation is divided by three so that the "value" of Earth is set to 1.

I sent the table to a friend (the same one who had sent me that fan video of the Death Star blowing up Yavin) and he suggested I post it for the truly geeky.

So, for what it's worth, here's my estimate of how relatively difficult it would be to blow-up different bodies in the Solar System.

Toughness to Blow-up
Sun 546,000
Mercury 0.365
Venus 0.874
Earth 1
        ● Moon 0.213
Mars 0.324
Jupiter 547
        ● Io 0.226
        ● Europa 0.190
        ● Ganymede 0.149
        ● Callisto 0.135
Saturn 286
        ● Rhea0.075
        ● Titan0.143
        ● Iapetus0.066
Uranus 26.0
        ● Ariel0.101
        ● Umbriel0.084
        ● Titania0.104
        ● Oberon0.099
Neptune 25.1
        ● Triton0.129
Pluto* 0.125
        ● Charon0.100
*Dwarf planet

Now the Death Star didn't just have enough power to blow-up Alderaan, it blew Alderaan away. If it had just blown-up Alderaan all the pieces would have been hanging out together there in space still held in proximity by gravity (like on Babylon 5 when the Vorlon Planet Killer reduced Arcata VII to a bunch of rubble). But the Death Star exploded Alderaan with enough power to overcome the force of gravitational attraction among the pieces. Or as Han Solo so eloquently put it, "No Alderaan.........It ain't there. It's been totally blown away." Meaning the Death Star hit Alderaan with a lot more force than necessary. (For a detailed look at that check out "Death Star Firepower.") How much more power it took to blow Alderaan away as opposed to just blowing it up into pieces that would hang out together and eventually reform into a new planet, I don't know. I'll let someone else figure that out. If it were 10X more power, (if you can give any validity to my table) then the Death Star wouldn't have been able to blow-up (not blow away, but blow-up) any of the larger planets. If it were about 25X more power than required, the Death Star would be capable of blowing-up (again, not blow away, but blow-up) ice giants like Uranus and Neptune.

As for what I think would have happened if the Death Star shot at Yavin........

I've already made it clear I don't believe there's a chance in hell the Death Star could destroy Yavin like it did Alderaan. An explosion would happen. How big an explosion, I don't know. Something the size of Jupiter's Great Red Spot maybe. But that's just a guess. If, like me, you've read Arthur C. Clarke, you're probably wondering if the blast could "trigger" a gas giant and turn it into a star, I offer this excerpt from Phil Plait's original Bad Astronomy site (back when it actually was about bad astronomy, hence novel & fascinating to read instead of what it is now --- just one of the many thousands and thousands of astronomy sites reporting on other scientists' work) considering the possibility of Galileo turning Jupiter into a star.

"Fusion is not a runaway process. Once you start it up, it generates a lot of heat, which tends to expand the material violently (this is what we technically call a bomb). This means the fuel gets scattered, and it won't fuse. Making really big hydrogen bombs run into this problem, making it hard to make really big bombs, which in my book is perhaps a good thing.

So the process tends to damp itself off. Jupiter won't explode. It won't turn into a star, either. Stars work by maintaining fusion in their cores. Now, I just said fusion isn't self-sustaining, so how do stars keep it going? They do it by containing the hydrogen in a small volume. This is accomplished by piling a lot of mass on top of the hydrogen: the mass of the star.

The star has enough gravity that all that mass squeezes and heats the core enough for fusion to not only take place, but to continue at a relatively stable pace. But it turns out there is a lower limit to that mass; if you don't have enough, then you don't get the high temperatures and pressures necessary to ignite fusion. That mass is about 0.077 times the mass of the Sun, or 80 times Jupiter's mass. In other words, Jupiter is 1/80th the mass it needs to turn into a star. Some people call Jupiter a failed star, but in reality it ain't even close."

Solar System Drawing

For more of my geekiness check out "The Old Yeller Abyss" or "The (Not So) Great Zombie Apocalypse." You can read more about movies or many other topics in the Archive.



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