The sun is getting hotter with age. The oceans will evaporate in one half to one billion years from now. No stars actually collide in a galaxy collision anyway, any more than they do now. But it will result in a huge star burst—all the dormant gas being converted into new stars suddenly, and then no more after that.
Arrrgghhh you're one of those climate change guys! No doubt all this is caused by carbon not being taxed high enough. Let's put meters on everyone's nostrils and anuses. Don't forget cow flatulence! Ban the hamburger! Everybody must be vegan by tomorrow morning! (ahem, but I thought beans cause ga. . .) OOOOHHH horrors! A denialist! Call out the tanks and planes! Bomb it out of existence! Look! It ran into the old growth forest! Burn it to the ground! It's the only way we will be sure the denialist devil won't live to spread its evil, vile climate denialism. Whatever it takes, we must root such thought out before it pollutes us! Whew! That was close. Cough, hack. Wheeze! It took only forty square miles this time. Bo y it's smokey around here. See what such thinking leads to? When will they learn how dangerous such thoughs are? We have to save the world from such insanity ever getting lose.
Sorry. . . I think I just had a linkage into a Liberal ecofreak's wet dream. . .
Mere engineering! As the Sun's increase is estimated to be .01% every million years, all that is needed is to adjust Earth's orbit correspondingly. Small matters about the Solar System equilibrium will obviously have to be taken into account but that is just basic physics.