Yea; 25,000 light years x 18 (number of halos last i knew) = 450,000 light years (cubed) the milky way galaxy is 126,000 light years in diameter (so A=4Pi x r^2= 4.99 x 10^10) Milky way is= 49,900,000,000 light years (roughly and only 2/3-5/8 is inhabited by the disc of the galaxy) Halo range is 9.1125x 10^16 So yea it can take out all life in the galaxy. But you should know: 450,000 or 4,500,000 times 1,000,000,000,000 (one trillion) average human life forms DOES NOT EQUAL the mass/weight OF MARS (1/3 the size of earth; 1/3 to 1/5 the mass) (4.5x10^18 average humans is barely equal to 6.39x10^20 metric tons, mass/weight of mars. Not sure if 4.5x10^18 is 450,000x 1 trillion or 4,500,000 x 1 trillion is all. I AM SURE on the rest tho)