Como você aponta a arma Starkiller?

1. Sabemos que ele pode ser direcionado e com muita precisão . Eles foram capazes de decidir destruir todo o sistema de estrelas OU uma base nele (mas deixar os outros planetas intactos).

   (com toda a justiça, este último parece contradizer o ponto # 4 abaixo. Bem-vindo ao J.J. Abrams "canon": (

   Though visibly angry, Snoke’s tone remained unchanged. “Have we located the main Resistance base?”
   Hux was clearly gratified to be the bearer of good news. “We were able to track their reconnaissance ship back to the Ileenium system. We are coordinating with our own reconnaissance craft in the area in order to lock down the specific location of their base.”
   Snoke replied with cold satisfaction. “We do not need it. Prepare the weapon. Destroy their system.”
   Collected and composed as he was, Hux was not immune to surprise. “The system? Supreme Leader, according to the most recent galographics, at least two and possibly three habitable worlds circle Ileenium. Following the destruction of the Hosnian worlds, would it not be worthwhile simply to destroy their base and claim the remainder for the Order? We will have the location of the base within a matter of hours and—”

2. Veja o que aconteceu quando eles dispararam o dispositivo. Observe a parte em negrito, o que significa que o próprio planeta estava apontando a arma, alinhando seu caminho.

   Dito isto, diz-se "linha de saída artificial", sem maiores detalhes - o que PODE significar que há pelo menos alguma flexibilidade em como essa linha é fornecida (supondo que a contenção da linha seja baseada em energia, e não simplesmente uma longa buraco estreito perfurado na crosta do planeta).

   When the weapons engineers fired the device, a breach was induced in the containment field. At incredible velocity and accelerating exponentially, the concentrated volume of quintessence escaped, transforming as it did so into a state known as phantom energy and following the artificial line of egress that had been provided. Assuming that the rotation and inclination of the planet had been taken into account, the released blast of concentrated phantom energy would travel along a perfectly linear path, punching a small Big Rip through hyperspace itself until it left the galaxy —
   — or encountered something in its path that was of sufficient mass to intercept it.

3. A arma dispara pelo hiperespaço (ou melhor, sub-hiperespaço).

   A novelização de Foster cobre detalhes da arma:

   Wexley spoke up. “They’ve built a new kind of hyperspace weapon within the planet itself. Something that can fire across interstellar distances in the equivalent of real time.” His expression showed his incredulity. “I’ve had my share of technical training, but I can’t even imagine how that’s possible.”
   This time Finn responded. “I can’t, either, but those of us assigned to the base heard rumors that it doesn’t operate in what we’d call normal hyperspace. It fires through a hole in the continuum that it makes itself. Everybody was calling it ‘sub’-hyperspace. That’s how it can arrive in moments across a distance like that between the base and the Hosnian system.

   e

   Finn nodded. “General Hux told us it’s the most powerful weapon ever built. He said that it can reach halfway across the galaxy.” Fresh murmurs of disbelief greeted this latest assertion. “And in real time. Because it doesn’t reach across the galaxy; it reaches through it.” He shook his head, which was starting to hurt from the effort of trying to explain what he had overheard but did not understand.

   E aqui está como o tiro real em Hosnian Prime é descrito:

   Traveling faster than anything ever generated by artificial means, through a torn portion of space-time whose properties were not fully understood, the concentrated glowing ball of energy lit the night sky above Republic City. ... It was as if a minuscule sun had suddenly appeared from nowhere, heading directly for the world on which she stood.

4. Ligeiramente offtopic, mas a especulação em outra resposta aqui que 4 raios separados eram para 4 alvos separados NÃO estava correta. O que destruiu outros planetas no sistema de Hosnian não foi carga separada da arma, foi a explosão de Hosnian Prime:

   ...Turning the planet into what astrophysicists called a pocket nova.

   Expanding outward from the explosion, a tremendous burst of heat tore through the Hosnian system’s other worlds, searing their surfaces clean of life and incidentally obliterating all settlements, installations, and outposts, as well as the hundreds of ships belonging to the Republic fleet. In its wake, the detonation left behind a blazing, spherical mass. The home of the Republic had become a new binary system: one utterly devoid of life.

Obviamente você não pode mudar a órbita ou o posicionamento do planeta, pelo menos sem afetar seriamente o clima, a gravidade e as condições ambientais até onde a vida no planeta é impossível ou até mesmo destruí-lo completamente ... então deve ser algum grau de controle sobre o raio disparado.

Na verdade, a cena em que quatro planetas são destruídos com um único disparo da arma incute essa idéia, pois o que inicialmente é um único feixe se divide em quatro feixes diferentes que parecem curvar levemente suas trajetórias para alcançar diferentes alvos amplamente separados.

Meu palpite é que há algum tipo de "transportadora" dentro do feixe que pode conter a energia para o impacto e guiar ou seguir um caminho determinado para o alvo.