Just look at how they shine their light brightly and spread their shine in a showery trail behind them.

Here's my idea. Comets are made up of water and carbon based molocules. We hop on one as it passes nearby with some (nuclear) device to provide heat. We melt the inside out and live inside it. We create artificial light to grow plants to live off. We split the hydrogen off the H20 to use as fuel for the engines we attach to the outside to deviate it from it's path and point it towards some other planet.

Sound fun?