Tekuo, astronomy and hard sums

My study area lies on Tekuo, an Earth-like planet inhabited by sentient hominids. Tekuo is one of six planets orbiting a class G2 sun, known as Aiu. The first three planets in the system are rocky. Tekuo is the second of these. Three gas giants lie in the outer part of the system. Tekuo lies in the habitable zone.

Aiu has 1.02 times the mass of our sun, Sol. The luminosity of a body is the cube of its mass, which makes Aiu 1.07 times as luminous as Sol.

It is surprisingly important that Aiu is brighter than Sol because Tekuo lies further from Aiu than Earth does from Sol. The distance from Aiu to Tekuo is 1.03 times the distance from Sol to Earth. This distance is the square root of Aiu’s luminosity and hence the distance at which Tekuo receives the same amount of light as Earth.

The time it takes a planet to orbit a sun is the square root of the cube of the distance between them. So Tekuo’s year is equivalent to 1.05 Earth years, that is to say, 385.33 days. A day on Tekuo lasts (in Earthly terms) for 24 hours and 15 minutes.

The radius of Tekuo is around 0.9 times that of Earth. This makes the size of the planet around 80% that of Earth.

Earth has a single moon, 0.0123 times its size. Tekuo also has a single moon, called Sũba. Sũba is around 0.011 times the size of Tekuo. It orbits its host planet in 23.5 days.

By David Johnson

Conlanger, writer and activist.


  1. I’ve added in the length of the Tekuan day, now I’m confident I can do so. I am now satisfied that the length of the day can be set independently of the other factors discussed above. It depends in part on some of the factors discussed above but also on the speed at which the planet is moving. This has, conveniently, not been mentioned.

  2. 07.07.19: I now have a full vision of the solar system. Tekuo is now the second planet out instead of the third. It only has one moon now, instead of two. This makes the calendar much easier!

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