Tag Archives: Astronomy

Astronomycast: What if Something was Different?

Astronomycast #246 deals with the question: What if something was different? What if any of the parameters of the universe was different, what if we were further out in the galaxy, what if we didn’t have gas giant, and similar topics – this is of great interest to a world-builder because it gives you a good basic framework of what does and doesn’t work in your fictional universes. AstronomyCast is a good podcast at any rate, I recommend it highly.

The Andiope Doublet (ESO)

Plot-a-Day: Ten Uses for Asteroids

Asteroids. Big lumps of rock and metal floating in the endless void of space. The Dawn probe is about to enter orbit around Vesta, where it will stay a year before moving on to Ceres.

The Andiope Doublet (Image credit: ESO)
The Andiope Doublet (Image credit: ESO)

So I was wondering: What can you actually do with Asteroids? They seem pretty useless, but here are some ideas:

  1. Prisons: Try to escape from a ball of rock a few hundred kilometers in diameter, literally out in the middle of no-where. Good luck.
  2. Mining: Some asteroids contain valuable metals or minerals or even tiny primordial black holes, and could be a source of conflict if more than one party claims them.
  3. Warfare: Use them as a military base or crash them into a planet. It ensured victory over the dinosaurs.
  4. Secret hideout: Pirates, spies, alien invaders, mad scientists, religious fanatics, the Space Mafia, rich eccentrics, anybody who wishes to remain out of the limelight for a while may set up shop on an asteroid.
  5. Space ship: Hollow them out, put in quarters and a big drive system, and ride a chunk of rock to the stars. In theory you could even use the rock of the asteroid itself as reaction mass.
  6. Waystation: Use it as a refueling and resupplying depot on your way to the outer system, or assemble your first FTL ship using that asteroid as a base.
  7. Monuments: What better place for the grave of your early space heroes than an asteroid cemetary?
  8. Natural Hazard: Very dense asteroid belts might actually pose a hazard to spaceships. The asteroid belt in the Solar System doesn’t; but it’s a staple of Space Operae to posit belts where asteroid tumble about chaotically and close enough to each other to constantly bump into one another. If a belt is created within the story’s timeframe, say by destroying a planet, it could become a new hazard to hyperspace lanes or what have you.
  9. Doomsday: In fiction, asteroids have a habit of constantly crashing into Earth or other inhabited planets. The players could either be helpless to stop it, and need to deal with a society gone wild in expectation of doomsday, or are heroic heroes that get sent into space to help Bruce Willis blow up that approaching menace.
  10. Mystery: Back in the days, people thought the asteroids might be the left-over of a fifth planet that was ripped apart. They don’t have enough mass, among other things, so this seems no longer plausible. That doesn’t mean it isn’t true in your fictional universe – and it might be the origin of asteroid belts in other systems. The players could hunt for artifacts from the fifth planet, prevent a similar fate from befalling Earth, could encounter Aliens in cold sleep, survivors from the catastrophe; or they could travel back in time to prevent the disaster (or, in a twist, cause the disaster in the first place to keep the timeline intact).

What other uses could asteroids have in adventures? How have you used asteroids in your games or stories?

Arnâron by the Numbers

GURPS Space provides a handy collection of rules, guidelines and formula to calculate all characteristics of a planet. I am not a sucker for 100% scientific accuracy, but I like to have at least some plausibility on my side when it comes to these things – I’ll at least try to avoid pulling off a Niven. Doing all these calculations was way too complicated (and quite honestly GURPS Space could use a lot of editing to make it easier to use in that chapter) so I am sure I made a mistake here or there. I won’t go through the whole process in this post, it would be boring as hell.

The Sun

Spectral class: G0V
Solar masses: 1.1 Sol
Age: 3.9 billion years
Luminosity: 1.66 Sol


Orbital Distance: 1.26 AU
Orbital period: 1.35 Earth years (492.38 Earth days)

Rotational period: 25h (Sidereal), 23.09 hours (apparent length in standard hours)
Year: 492,38 standard days, 511.81 local days
Axial tilt: 17°

Diameter: 8919.4 km (0.7x Earth)
Circumference: 28021.12 km
Surface Area: 249931591,24 km^2
Hydrographic coverage: <10%

Mean density: 6.62 g/ccm
Gravity: 0.84 Earth

Average Temperature: 314 Kelvin (40.85° Celsius)

Atmospheric pressure: 0.92 atm

Number of moons: 2

Moon 1: Orbital distance: 240,000 km, Diameter 1129km, Apparent orbit 1.26 local days

Moon 2: Orbital distance: 410,000 km, Diameter 2113km, Apparent orbit 1,09 local days


Arnâron is a world significantly smaller than Earth – only about 70% its diameter – and consequently has a lower gravity than Earth, and a thinner atmosphere. Both are perfectly within the human comfort zone, but the inhabitants of Arnâron will have more efficient lungs (or simply require less oxygen to function, or have much lower stamina…) and they’ll be somewhat weaker and more slender than Earth humans.

The sun is slightly larger and hotter than our Sun; Arnâron orbits much further out from its primary than Earth and is still much, much warmer. Luckily, the thinner atmosphere is able to retain less heat. The lack of temperating oceans means that the differences in climate between the poles and the equator will be much more severe. This was different in the past, where Arnârons now dead oceans played a much greater role in keeping certain areas habitable than they do on Earth.

The local day of 23 standard hours worked out pretty well, it won’t require much adjustment from players, readers, or displaced Terrans. The longer local year will influence local culture and customs, but won’t pose a problem to the human rhythm of life.

Arnâron will have normal, but slightly less tectonic activity than Earth (less water means less movement of the plates), and roughly the same amount of volcanism.

The moons will be very visible from the surface: With angular sizes of 16.2 minutes and 17.7 minutes, respectively, they are each seen as about half the diameter of Luna from Earth. This worked out to slightly smaller than I had intended, but if I make them much larger or closer, tidal effects will slow down the rotation of Arnâron too much – I really like to have a day that’s relatively close to 24 standard hours.

Another concern I have is that the world may be too hot. This could easily be changed by making the sun dimmer or by changing the orbit, without much effect on the overall design, so I’ll keep the current value for now.