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The James Webb telescope reaches its observing post in space – Lagrange point 2. Astronomers love this place.
Almost a month ago, the largest space telescope to date was launched into space. After a 1.5 million kilometer flight, the James Webb telescope has now arrived at its destination: Lagrange point 2.
There are five Lagrange points in the Sun-Earth system. These places are particularly exciting for space travel because they are a kind of parking lot for telescopes and satellites.
Advantages of the Lagrange points
“At a Lagrange point, you don’t need a lot of fuel to keep the mission there. That’s one of the big advantages,” says Florian Renk from the European Space Agency ESA.
At the Lagrange points, flying objects orbit the sun with almost no propulsion of their own. And no matter where you are when you are orbiting the sun, your position in relation to Earth always remains the same.
The Bernese astrophysicist Susanne Wampfler explains how this is possible: “A force is always required to keep a body on a circular path. You see that with the hammer throwers, who first spin the hammer and when they release it, it keeps going straight because there’s no more force acting.”
Would be the James Webb telescope somewhere in space, it would often have to use a lot of its own energy – or fuel – to keep its orbit around the sun. At the Lagrange points, the gravitational forces of the sun and the earth combine in such a way that a small-mass body, a satellite or a telescope, can move around the sun synchronously with the earth.
L1 for sunbathers
The fact that the telescope “parks” Lagrange point 2 has the advantage that we can communicate well with it down here on Earth, despite the great distance. In addition, the telescope can be kept cold at this most distant Lagrange point. This is crucial for the proper functioning of the infrared telescope, which is designed to detect extremely fine thermal radiation, for example from the earliest stars.
Other star observation missions such as the European GAIA telescope are also not here by chance. On the L2 you always have the sun and earth behind you and a clear view of the depths of space ahead.
The L1 Lagrange point on the opposite side of the earth facing the sun offers other advantages, says Susanne Wampfler: “L1 is mainly used for missions that study the sun, such as the Genesis mission, which studied the solar wind.”
Locations for special missions
Around a dozen active telescopes and satellites are currently sending their data back to Earth from Lagrange points. So very few compared to the 4,000+ active weather, communications, and other satellites orbiting the earth.
There is a reason for this: Lagrange missions are many times further away and correspondingly expensive. You can’t do business with it either, says Susanne Wampfler from the University of Bern: “Research missions lead to the Lagrange points, which don’t bring us television or internet reception, but rather new insights into the universe.”
The findings of the James Webb telescope are being followed with interest around the world. First data are expected for the summer.