Artifexian – Lagrange Points and more Trojan Ramblings

Sick of having just one planet per orbit? Need a location for your space habitat? Want to construct an interplanetary highway linking the various worlds in your system?…Welcome to the wonderful world of Lagrange points.



Here’s a little extra bit which was excluded from the video but was discussed down in the videos comments.

For added realism, place a terrestrial planet at the L4/L5 points of a gas giant. Why? Well, for ideal stability, the ratio of the masses between the secondary object (think earth) and a lagranian planet should be roughly 25:1.

That is a lagranian companion should not exceed 4% the mass of your main planet.
4% the mass of a terrestrial planet is doable…but bordering on implausible
4% the mass of a gas giant is a whole lot more plausible.
Plus setting up a system where the earth analog is a lagranian companion of a Hot jupiter say, brings that extra level of exotica to a setting.

A knock on effect of this this 25:1 mass ratio, is that a lagranian companion world is unlikely to have its own lagranian companion. This is because, by definition, lagrange points arise out of a thing called the restricted three body problem: three bodies, no more!
An orbit with a different, yet equally massive planet every 60 degrees is, simply put, utterly implausible

Unless your watching something like Firefly…THEN EVERYTHING’S PLAUSIBLE!

Happy Christmas everyone, look forward to hearing your lagranian anecdotes down in comments.

…Edgar out!

  • John H Reiher Jr

    Speaking of Lagrange points, one theory about the origin of the Moon concerns where the planet Theia formed. One theory has it forming in the Proto-Earth’s L5 point and once it got big enough, about 10% Earth’s mass, it left the L5 point and wobbled it’s way to a collision with the early Earth.

    • This is true, and definitely has applications in scifi. Well pointed out, John.

      • One of the most common being used as orbital mines (and sometimes called Natural Resource Satellites, such examples here: ). And considering that according to the Wikipedia page John linked, it takes less energy to reach than our own Moon, it would actually be more economical and less problematic if something goes wrong ala “Armageddon” ( ) to move them at Earth’s Lagrange Points than within Earth Orbit such as the above links in the Moon’s Lagrange Points.

        Still, it kinda kills the romantic idea of asteroid fields in close proximity to Earth. But maybe that’s a good thing?

    • Bejesus, that’s fascinating!
      Does that mean there should be a huge amount of Trojans and L5 moons out there (because their formation is ‘normal’)?

      • John H Reiher Jr

        There’s just one that we know of so far: 2010 TK7. There may be more, but not many folks are looking. That may change. More on Earth’s Trojans here:

  • Paulo R. Mendes

    I would love to build a interplanetary highway (like those from Freelancer) linking the worlds of my system… 🙁

  • never really thought to much about Lagrange points. but it does open up a huge list of possibilities and potentials! 😀