Lagrange points are special spots in space where an object remains relatively stable. At these points, gravitational forces of two big objects (for example – the Sun and Earth), perfectly balance the force required for a small object (spacecraft) to move in an orbit in a constant pattern.

In 1772, an Italian mathematician and astronomer named Joseph-Louis Lagrange, successfully tackled the general three-body problem*, and discovered these points. So, thanks to Lagrange, we know these unique places exist in the vastness of space!

There are five Lagrange spots named L1 to L5. Space scientists love these spots because if a spaceship reaches there, it doesn’t need a lot of fuel to stay in the orbit. These five points in the Sun-Earth system are shown here.

Here are some fun facts about Lagrange points:

• L1, L2 and L3 are unstable points. If a spaceship wants to stay there, it has to keep adjusting itself all the time. They all lie along the line connecting the Earth and the Sun.
• L1 is like having a front row seat providing an uninterrupted view of the Sun. In the next article, explore the journey of Aditya L1 as it makes its way to L1.
• L2 gives our telescopes a clear view of deep space because the Sun, Earth and Moon never block its view.
• L3 is always hiding behind the Sun. Scientists have dreamed about hidden planets being there.
  However, at present, it makes for good science fiction.
• L4 and L5 are stable points located close to the Earth’s orbit. These points are like being right on the apex of two big triangles in space. If a spaceship goes there, it can stay put without much effort.

*The three-body problem is a classic problem in physics and space science that involves predicting the motion of three big bodies. Each body exerts a gravitational force on the other two bodies, resulting in a constantly changing net force on each body. Also, their velocity and relative position add further complexity. Thus, it is very challenging to accurately predict their future positions and velocities. However, the Lagrange point is a wonderful discovery because if a small object is placed at the Lagrange points in a two-big-body system (such as the Sun-Earth system), the object remains relatively stable.

About the writer:  

Tulika is an alumna of NIT Jamshedpur and IIM Lucknow. She is the founder of Periodic Table Game Atomics and myschoolz.com—a platform that helps parents find the right school for their kids. Before venturing into entrepreneurship, she worked for Hewlett Packard, Alstom, and Vedanta. Her passion for writing for children stems from the belief that kids are incredibly curious and always ready to explore new things. Through her writing, she aims to foster a love for learning in the next generation.

Click here for Part 3

Sources

Aditya-L1 Mission | ISRO

What is a Lagrange point | NASA