Theoretical Orbits of Planets in Binary Star Systems
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A binary star system consists of two stars which orbit around their joint centre of mass. A large proportion of stars belong to such systems. What sorts of orbits can planets have in a binary star system?
To examine this question we use a computer program called a multi-body gravitational simulator. This enables us to create accurate simulations of binary star systems with planets, and to analyse how planets would really behave in this complex environment.
Initially we examine the simplest type of binary star system, which satisfies these conditions:-
1. The two stars are of equal mass.
2, The two stars share a common circular orbit.
3. Planets orbit on the same plane as the stars.
4. Planets are of negligible mass.
5. There are no tidal effects.
We use the following units:-
One time unit = the orbital period of the star system.
One distance unit = the distance between the two stars.
We can classify possible planetary orbits into two types. A planet may have an internal orbit, which means that it orbits around just one of the two stars. Alternatively, a planet may have an external orbit, which means that its orbit takes it around both stars.
Also a planet's orbit may be prograde (in the same direction as the stars' orbits ), or retrograde (in the opposite direction to the stars' orbits).
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Copyright 2001 S.Edgeworth