Posted by drdave on September 3, 2009
|
In the vicinity of two bodies in space that orbit each other lie five Lagrange points, named after Joseph-Louis Lagrange, the French / Italian mathematician (1736-1813). Lagrange made major contributions to various branches of mathematics, and discovered the Lagrange points in 1772 while working on the three body problem, first described by Sir Isaac Newton in 1687.
The diagram at the left shows the location of the five points. The Earth-Moon system has five Lagrange points, commonly labeled EML-n, and the Sun-Earth system has five points, labeled SEL-n:
- L-1 is, as one might suspect, located between the two bodies, where the gravitational pull of each body equals the other. This point is unstable. That is, if a satellite deviates in any way from the point, it will fall into the gravity well of one or the other bodies. The Solar and Heliospheric Observatory (SOHO) is located at SEL-1 in a Halo Orbit.
- L-2 is beyond the smaller body, where the combined gravitational pull of the two bodies balances the centrifugal force of the satellite. Satellites currently at SEL-2 include the Wilkinson Microwave Anisotropy Probe, the Planck space observatory and Herschel Space Observatory. L-2 is also an unstable point, and all three satellites occupy Lissajous orbits around the Lagrange point
- L-3 lies beyond the larger body away from the smaller body. SEL-3 is on the other side of the Sun from the Earth.
- L-4 lies at the corner of an equilateral triangle whose base is between the two bodies, ahead of the direction of the orbit of the smaller body. The Trojan asteroids occupy SJL-4 and SJL-5 of the Sun-Jupiter system. Both L-4 and L-5 are stable, as shown by the gravity contours in the diagram.
- L-5 lies at the corner of an equilateral triangle whose base is between the two bodies, behind the direction of the orbit of the smaller body. EML-4 and EML-5 were popularized by G. K. Oneill as places to build human space colonies. This was the impetus for the founding of the L5 Society.
Wikipedia has an excellent article on Lagrange points in space.
|
Image from notes by Neil J. Cornish from the NASA WMAP Wilkinson Microwave Anisotropy Probe web site.
|
This entry was posted on September 3, 2009 at 11:03 am and is filed under Space, Space Exploration, Space Settlement.
Tagged: Dr. Gerald K. Oneill, Earth, Halo Orbit, Jupiter, L5 Society, Lagrange, Lissajous orbit, Moon, Satellite, Sun, Trojan asteroids. You can follow any responses to this entry through the RSS 2.0 feed.
You can leave a response, or trackback from your own site.
Post Augustine Commission – ULA Says “Fly Me to The Moon” « The National Space Society of Phoenix said
[...] Lagrange Point [...]
The Augustine Commission – Bad Day at Black Rock – And a Reprieve « The National Space Society of Phoenix said
[...] to low Earth orbit and a return by NASA to exploration. Near Earth Objects (NEO), the Lagrange points and space observatories, building and deploying propellant depots and Phobos as a destination were [...]
JWST – James Webb Space Telescope « The National Space Society of Phoenix said
[...] and Misses – Part 2Space News – September 2009Galactic Cosmic Rays (GCR) – The 800 Pound GorillaLagrange PointLunar Exploration Summer Intern Program [...]
The Augustine Commission – Final Report – Hits and Misses – Part 5 « The National Space Society of Phoenix said
[...] Posts Mind The GapLagrange PointSoyuz Launch – 10 November 2009 – Poisk to ISSJWST – James Webb Space TelescopeAugustine Commission [...]