That's [b][i][u]if[/u][/i][/b] they are limited to planets in the goldilocks zone. This is a super advanced race, I'm certain they have technology that allows them to colonize less habitable worlds. Who says they are limited to the surface? The forerunners, not humans, have hundreds upon hundreds of planets like coruscant [b][i][u]that they artificially created[/u][/i][/b] I'm saying calculate how much mass could the rest of the 99.999% of the energy destroy. That's the true potential of the halos.