Planetery Vaporisation.

[NecronLord]

I am currently wondering about the calculations for vaporising (though not all at once, there is evaporating debris for about a minute) an earth-like planet.

Taking the Gravitational Binding energy to be 2.4E32 joules, do we simply add the vaporisation energy?

Also, would anyone know where there's a good list of the earth's composition and evaporation points of elements?

[SirNitram]

Personally, I always went conservative and did it as a giant sphere of iron.

But, this will come as a shock, the answer will probbaly be below 1e32J. It costs less to vaporize the Earth than to blow it apart violently.

[Grand Admiral Thrawn]

You vap the Earth, it'll cool down eventually and reform.

[His Divine Shadow]

Assuming earth is made of iron.

Volume = 1.098e21m^3
Iron Density = 7870kg/m^3

Hence total mass: 8.6e24kg

Energy required to vaporize 1kg of iron = 7.63 MJ/kg

Therefore, total energy required to vape the earth if it was made of iron:
6.5e25j

[Ted C]

Assuming earth is made of iron.

Volume = 1.098e21m^3
Iron Density = 7870kg/m^3

Hence total mass: 8.6e24kg

Energy required to vaporize 1kg of iron = 7.63 MJ/kg

Therefore, total energy required to vape the earth if it was made of iron:
6.5e25j

Did you take into account that the temperature of much of the Earth's mass is already above the melting point of iron?

[His Divine Shadow]

Assuming earth is made of iron.

Volume = 1.098e21m^3
Iron Density = 7870kg/m^3

Hence total mass: 8.6e24kg

Energy required to vaporize 1kg of iron = 7.63 MJ/kg

Therefore, total energy required to vape the earth if it was made of iron:
6.5e25j

Did you take into account that the temperature of much of the Earth's mass is already above the melting point of iron?

No, I was being pretty basic here.

[NecronLord]

Sorry that I didn't make it clear it was not just vaporised but blown apart very violently at the same time:

"Opening her eyes, she stared at the screen. Terakis was gone - no more than rubble and vapour, expanding rapidly in space from where the planet had once been."

followed shortly by...

"The gas cloud that had been Terakis was now almost completely invisible.”

[NecronLord]

Now I think about it, couldn't you work out the density needed to be 'almost invisible' and work back from that?

[Darth Wong]

The energy required to blow apart the planet is greater than the energy required to vapourize it, by an order of magnitude or more (remember that there is a such thing as a gas planet). Therefore, you should just use the standard figures and not worry about it.