Orangutangents

Interstellar Suns

I do like a bit of SciFi geekery as you know, and there was a wonderful article I saw on io9.com a while ago about whether we'd first notice alien life (if interstellar aliens exist of course) by their constructs. The premise of that one was pretty much along the lines of "If aliens want to travel interstellar distances would they bring their star with them?"

Now at the time there was a lot of talk about Dyson spheres (a sphere built around a star with the 'land' on the inside of the sphere), but many folk pointed out that for an earthlike star, the size of the sphere (which would need to be about the distance between Earth and our sun, 1AU) would be massive. So a great deal of material would be needed to construct something that large.

So, instead of a sphere, how about a ringworld? Yes, that would work. A ring, with smaller rings inside to simulate the moon's shadow. But still, the size of the ring would be huge. The benefit of course from the sphere, capture and transport of your own sun is that you're used to the light / radiation of your home sun, and you can use solar power as your energy source.

There are of course holes in any theorem, but another more recent article did note "Why should the star be the same as our sun?" 

If a white dwarf star (a dim stellar remnant left over after a star like our sun explodes) was used instead, then the habitable zone would be a lot closer, the sphere smaller, and thus the amounts of material used to construct a ring or Dyson sphere considerably less.

Again, there are many questions about the materials used etc, but this would be technology far in advance of our own, so we'll give the virtual aliens making it a little credit for knowing which end of a spanner to use.

But, there's a catch. With a travelling sun-like sphere, we'd possibly detect it due to sheer size or radiation. But white dwarfs are less luminous, and so the infrared emissions from a white dwarf Dyson sphere would be much harder to detect. 

As with all potential alien visitations, the first we might know is when it's a little late to do anything other than hang out the flags, put the kettle on and say 'Welcome'. 

Will Smith, a jury rigged laptop with a laughing virus, and a couple of missiles ain't gonna do much against a species that can harness a star, drag it across interstellar space and build a massive sphere around it.

"Welcome interstellar travellers."