An Orbit is a mathematically closed path about a body in space by a ship or another body.
Standard Orbits are defined as a measure of distance from a central star or stellar remnant. These are are typically measured in AU or Astronomical Units. These should not be confused with Orbital Zones which are temperature bands of importance when modelling system evolution, resources and habitability.
Other Orbits are defined relative to the nearest/largest near astronomical body.
Standard Orbit Representation
Standard orbits are represented numerically from 0 to 145. By convention orbit 3 is at 1 AU. Orbit 145 is the edge of an Astrographic Hex or Parsec and always represent the far system where Oort Clouds and the Hill Sphere are located.
Types of Orbit
When two stars are relatively close together and the orbiting body a relatively long way away, Planets and Asteroid Belts may circle not the individual stars but the centre of mass of the pair. Such bodies are in Circumbinary Orbits.
Lagrangian Orbits inc. Trojan Orbits
Where one body orbits a second, there are stable and meta-stable points relative to the smaller body that can be exploited naturally (Trojan Points) or artificially. These are shown as L1, L2, L3, L4 and L5 in the diagram above. L2 is sometimes known as a Midnight Orbit as anything there is overhead on the smaller body at midnight. L4 and L5 are Trojan Orbits and are meta-stable - meaning that they may contain naturally occurring debris or even asteroids.
These orbits are found between the upper atmosphere (if any) and the inside of the planet's radiation belt. For a Terran-sized planet, the orbital times are measured in minutes or hours. These orbits are typically affected by atmospheric drag and will naturally decay onto the planet
These orbits are found outside the planets radiation zone. These orbits may include a Geostationary Orbit (i.e. an orbit where one transit of the orbit takes teh same time as one rotation of the underlying body) only if the planet is rotating at a speed that is significantly shorter than the planetary year. e.g. Terra has a Geostationary orbit at 36,000km; there is no equivalent for Luna.
High orbits end when the attractive force of another nearby astronomical object (Star or Moon) is greater than that of the Planet
The principles are similar to Planetary Orbits (above)
Swapping/Horseshoe orbits occur when two astronomical objects occupy almost identical standard orbits. That in the lower orbit will slowly catch up with that in the higher and become attracted by it - thus raising its orbit (slowing it) and lowering the other object's (thus speeding it up) until the two have swapped tracks and are now moving away from each other again. They never pass each other in space within their shared orbit.
Star System Locations
See Orbital Zone
Terran history shows that the concepts of Orbits were first discovered by Galileo, and developed by Johannes Kepler. Geostationary Orbits (and their implications) were first described by Arthur C Clarke.
Universal world profile
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