Constructing A Dark Sun and A Dying Earth

Art by Don Dixon

Still ruminating on my Dark Sun riff, I figure first things first: that dark sun. Smith and Vance provide the prototype. As the Smith writes in the "Dark Eidolon": "...the sun no longer shone with the whiteness of its prime, but was dim and tarnished as if with a vapor of blood."

Not that it needs to be even vaguely scientific, but the usual way people give this a scientific veneer is to have the Sun (or whatever star) have turned red giant in old age. In our solar system, current theory suggests the Earth will have been scorched by the Sun's increasing luminosity billions of years before it goes red giant and consumes the planet entirely, but again fantasy. Also, even a red giant star burns white hot, so would hardly be "tarnished as if with a vapor of blood," but that's seldom concerned sci-fi writers, and shouldn't unduly concern us.

Another option, rather than the very luminous red giant, is the small, dark, and cooler red dwarf star. It is true that our Sun (or any star) won't become a red dwarf as it's dying--in fact red dwarfs are very long lived--but hey magic or sufficiently advanced science, right?

A red dwarf wouldn't typically look red in the sky either, but it's light diffused through dust or clouds would definitely be more orangish, at least, and it would be dim enough that you could look at it and see flares and things on it's surface. Dim enough, and close enough, because the habitable zone of a red dwarf would be very close to the star, so an Earth like world would be huddled in like a person around a campfire on a cold night.

The thing about being so close to the star as that it would likely mean the world was tidally locked; It might well present the same face to the star at all times and have a dayside and a nightside. This could then be a world with a scorching day time desert and a freezing night time desert, but it also offers other possibilities. Of course, the planet could have a 3:2 resonance like Mercury, rather than a 1:1 tidal lock like the Moon, too.

So doing a little bit of calculation, and a little bit of making stuff up, here's what I came up with: An world tidally locked to a dwarf star. It's day side is a scorching desert, dotted with dead cities and desiccated sea basins from before whatever happened happened. On the day side over the equator, the sun would be white and a little over 3 times as large as the Sun is in our sky.  Further from the equator and the prime meridian (not as arbitrarily placed on a world where the sun doesn't move) the sun is lower in the sky and redder in color.

Moving toward the night side, the land would become a little less dry by stages until you reached the terminator (no, not that one) where there would be forest and jungle cloaked in eternal twilight and wracked by fierce storms caused by the meeting of the hot air from dayside and the cold air of the nightside. Here be monsters.

Most of the night side, lit only by the stars, is a cold ocean. As we all know places of eternal night are havens of undead, and so must it be here. And of course, sea monsters.