Lagrange Points | Parking place of Spacecrafts

In astronomy, Lagrange point is also called Lagrangian point or libration point, where a small mass object like a spacecraft will remain at approximately rest, under the gravitational influence of  two large bodies like the Sun and Earth. The objects placed in those points experiences the neutral force. So, these points serves as a “Parking spots” for spacecrafts, to remain in a fixed position with minimal fuel consumption.

For any combination of two-mass orbiting objects in space, there are five Lagrange points named L1 to L5. The Lagrange points L1, L2 and L3 are unstable and lie along a line that passes through the two large bodies. Whereas the L4 and L5 points are stable and each lie at the vertex of an equilateral triangle, they have the two large bodies at the other two vertices. Let’s have a look at Lagrange points associated with the Sun and Earth in this article.

L1 Point

The L1 point lies on the line defined between the two large bodies, where the gravitational attraction of both the masses acts and produces equilibrium. It lies in about 1.5 million kilometers from Earth in the direction of the Sun.

L1 point is suitable to monitor the Sun, since the constant stream of particles ( solar winds ) strikes here, about an hour before it reaches the Earth.

At present, the Spacecrafts of L1 Points are;

L2 Point

The L2 point lies beyond the smaller body and on the line through the two large bodies. At this point, the combined gravitational forces of the Sun and Earth balance the centrifugal force on a object. Like L1 point, L2 is also located at about 1.5 million kilometers from Earth in opposite side of the Sun.

L2 point is suitable for exploring the wider universe, since the shadow of Earth is avoided here.

At present, the Spacecrafts of L2 Points are;

• Gaia Probe
• Spektr-RG
• JWST
• Euclid

L3 Point

The L3 point lies beyond the larger body and on the line defined by the two large bodies. Bodies present at this point cannot be seen from Earth. The combined pull of Earth and Sun causes the object to orbit like same as Earth.

L3 point is suitable to study the Far side of the Sun.

At present, the Spacecrafts present of L3 Points are;

• None of the objects were placed in this point.

L4 and L5 Point

The L4 and L5 point lies on the center of the two masses, such that Lagrange point in one vertex and two large bodies on the other vertexes of the equilateral triangle. Unlike the other Lagrange points, L4 and L5 are resistant to gravitational perturbations.

L4 and L5 points are suitable to study asteroids and space dust, since its free from gravitational pull.

At present, the Spacecrafts/Asteroid noted in L4 Points are;

• Asteroid 2010 TK₇ – First discovered tadpole-orbit companion to Earth, orbiting L4.
• Asteroid 2020 XL₅ – Second Earth Trojan.
• Spacecraft STEREO – Made its closest pass to L4 in Sep-2009.
• Spacecraft OSIRIS-REx – Made its closest pass to L4 in Feb-2017.

At present, the Spacecrafts/Asteroid noted in L5 Points are;

• Asteroid 2010 SO₁₆ – Horseshoe companion orbit with Earth.
• Spacecraft STEREO B- Made its closest pass to L5 in Oct-2009.
• Spitzer space telescope – Made its closest pass to L5 in between 2013-15.
• Spacecraft Hayabusa2 – Made its closest pass to L5 during the spring of 2017.