Second Sun-Earth Lagrange Point

 The Second Sun-Earth Lagrange Point (L2) is a gravitationally stable region in space located approximately 1.5 million kilometers (about 1 million miles) directly "behind" Earth as viewed from the Sun. At this specific spot, the combined gravitational pull of the Sun and Earth provides exactly the centripetal force required for an object to orbit the Sun at the precise same rate as Earth.


  • Constant Alignment: Because an object at L2 keeps pace with Earth's orbit, it remains in a fixed position relative to the Earth and Sun.

  • Thermal Stability: L2 is ideal for infrared astronomy. A spacecraft can deploy a single sunshield to permanently block the light and heat from the Sun, Earth, and Moon, which all remain clustered in the same general direction. This allows instruments to remain incredibly cold and stable.

  • Unhindered View: Unlike in Low Earth Orbit (LEO), a telescope at L2 doesn't have the Earth continually passing in front of its targets or causing day/night thermal cycling.

  • Notable Satellites: This advantageous positioning makes L2 the current home of the James Webb Space Telescope (JWST), the Gaia space observatory, and the Euclid telescope, as well as the former home of the WMAP and Planck background radiation mapping missions.

While L2 is an equilibrium point, it is technically unstable (like balancing a ball on top of a hill). Satellites parked there must execute small, periodic orbital corrections (station-keeping) using thrusters to maintain their halo or Lissajous orbits around the exact L2 point.

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