ON LAST COUNT YOU’D killed twelve planets, but you still found that first quick slice to the jugular the hardest. You felt your own breath wet on your face in your crinkly hazard suit; worn to keep the dust off; needless, at least for the moment. You judged the angle. You hesitated.
Your unwilling tutor mistook your hesitation for anticipation, sitting opposite you in her own rustling orange suit, the triple light of the three-star sunset dyeing her face orange through the soft plex stuff of the hood. A light hail of sand and dust particles pattered over the fabric and went plinkety, plinkety, plink.
As you had never done anything tectonic in the past, it was with an edge of resentful fury that you lifted the hilt high above your head. You drove the point of the bone-sheathed blade into the talc—obviously you never wanted it to have an edge of any kind, ever again—and using the sword as your focus, drove a killing lance of thanergy right into the planet’s heart.
The planet did not quake, or howl, or freeze, or writhe, skewered on your necromancy’s tines. You began the cascade outward, as you had been taught. A wide thanergetic scythe sheared out into the mantle, deeper into the minute thalergy of the rock, into the solid stone’s buried recollections of the day its ball of dust was formed. So much more difficult, on a planet of this character; that was why Mercymorn had chosen it, along with the hope that you would end up an ice corpse. The thanergy reaction had to be carefully wrought. Here the soul of the planet was in the striations of its sand and minerals: a soft woven network of miniature creatures, of bacteria, of thin, stretched-out skeins of life. You had not even understood what to look for, the first time. Now you felt it as you felt the sand scouring the outside of your suit.
Less than sixty seconds later you were curled up on the surface of the planetoid, half-dead with cold, trying to flush your extremities and dilate your blood vessels. Wading out of the River had never been a problem for you; you were always happy to go. The night-stricken planet had not reacted overmuch—you prided yourself on being the knife that cut silently—but the sandstorm had died as though arrested in midair. Particles that had been whipped miles up into the atmosphere were pattering down like rain. It grew exceedingly dark as the suns set in unison, and Mercy had clipped a little light to her ever-present clipboard as she wrote, which created a tiny corona of her pen, and the clipboard, and the softly falling sand.
Harrow the Ninth kills a planetoid with an atmosphere, causing the sandstorms to instantly stop and start raining down. We can get an absolute minimum of the timeframe, as in total it took 8 minutes and 34 seconds (514s), but a minute of that was spent waking up after extinquishing the Minor Beast (the planetoids ghost).
Less than sixty seconds later you were curled up on the surface of the planetoid, half-dead with cold, trying to flush your extremities and dilate your blood vessels.
“One fewer for Number Seven to eat on the way in,” said the Saint of Joy. “Eight minutes thirty-four,” she added, because Mercy always lied when one thought she wasn’t going to, and never lied when one assumed she would, and mixed it up every so often to unbalance everyone further. “Not really good enough, Harrowhark.”
Ultimately it would have taken longer than that, as Harrow spent a lot of that time fighting the Minor Beast in the River (plane of undeath), but as an absolute low end this can work. As the world is refered to as a planetoid but still has an atmosphere, we'll use Mercury as our example, which has a diameter of
2440km.
T = 514s - 60s
= 454s
T = 2440km/454s
= 5374.44934/340.29
= Mach 15.7937328
Now we have our speed, we'll go about getting out energy. To find the volume of our atmosphere, we'll go with the minimum of "miles up" (that being at least two miles, or 3218.688m) and subtract it from the volume of our planet.
R = 2439700m + 3218.688m
= 2442918.69m
V = 4/3πr3
= 4/3 X π X 2442918.69^3
= 6.1068274e19m^3
V = 4/3πr3
= 4/3 X π X 2439700^3
= 6.08272087e19m^3
V = 6.1068274e19 - 6.08272087e19
= 2.410653e17m^3
M = 2.410653e17 X 1.003kg
= 2.41788496e17kg
Sandstorms have a minimum speed of
40km/h (11.1111111m/s). However, we unfortunately don't know if the storm covered the entire planet or not (given how huge the sandstorms are it's a possibility, but in anycase we'll need a low end). So, we'll use a low end of a light breeze (being at least 4 miles an hour, or
1.78816m/s). As a high end, we'll go with
60 miles an hour (or 26.8224m/s) for Martian sandstorms.
(Low end)
KE = (0.5)mv^2
= (0.5) X 2.41788496e17 X 1.78816^2
= 2.16178259e17 joules
= 51.667843929254303248 megatons
(Mid end)
KE = (0.5)mv^2
= (0.5) X 2.410653e17 X 11.1111111^2
= 1.99339763e19 joules
= 3.5565425430210324542 gigatons
(High end)
KE = (0.5)mv^2
= (0.5) X 2.410653e17 X 26.8224^2
= 8.67161473e19 joules
= 20.725656620458892121 gigatons
Final Results
Harrow scythes her 12th planet = >Mach 15.794
Side effects of Harrow killing her 12th planet (low end) = >51.668 megatons
Side effects of Harrow killing her 12th planet (mid end) = >3.557 gigatons
Side effects of Harrow killing her 12th planet (high end) = > 20.726 gigatons
Just to finish up, I feel this is a huge lowball (for energy in particular), as not only did she kill an entire planet, but comments on avoiding anything tectonic. In anycase if anyone has doubts, this should still serve as a good (hyper) low end.