Why do they send the James Webb telescope a million and a half kilometers?

At this distance, repair is impossible if something goes wrong. What’s so special about that exact spot in the cosmos that the James Webb super telescope is aiming for?

That the universe is full of wonders is hardly debatable, but there are points in space that border on magic. Physicist Gerard O’Neill suggested in the 1970s that humanity could one day move into floating houses located on a Lagrange point between the Earth and the Moon. These are spaces so unique that you can put something in them, a satellite, a houseboat for humanity or a super telescope like James Webb, without moving, without fleeing to the vastness of the cosmos.

One of these points was chosen to locate James Webb, the astronomical observatory which is scheduled to launch on December 24th.

They are called Lagrange points by the mathematician and astronomer. Joseph-Louis Lagrange, who discovered them, and we could imagine them as stops in the universe, rest areas. Located at these points, an asteroid, spacecraft, or dust cloud remains there, suspended by the invisible forces of gravity, and needs only a minimal amount of energy to correct its course in the event of a loss.

These points exist because celestial objects, in their ceaseless motion, attract each other and, at various specific points, the gravitational fields of two massive bodies (such as the Sun and the Earth) are balanced. This “zero” zone are the spatial “parking areas”, the Lagrange points.

There are many of these unique points in space as a result of the balance of gravitational forces from different objects in the solar system, but there are only five that result from the balance between the Earth and the Sun.

L2, James Webb’s Icy Parking Lot

One of them, the L2 point, is 1.5 million kilometers from Earth in the opposite direction from the Sun. This means that placing a satellite there, or a telescope like James Webb, allows its solar panels to be directed towards the Sun to be attracted it gets the energy it needs to correct course if necessary, and at the same time, your telescope’s spectacular mirror can be directed outward into the solar system. With the sun and Earth at your back, Webb’s gold-plated mirrors will have an unobstructed view of the universe.

The video shows how James Webb will move, as if he were tethered to the Earth in its orbit around the Sun:

There are more reasons to choose L2 over L1, which is closer to Earth. In order for Webb to function properly and to be able to collect infrared light (which is heat after all) from very faint and distant objects, the telescope must be very cold. In the shaded area of ​​L2, where the sun is strong, it will be -233 ℃. At this temperature, the super telescope is sensitive enough to detect the embers of objects that could have formed at the origin of the universe.

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From here, the telescope can see everything from planets in our solar system to the most distant galaxies. Webb will orbit too far for any astronaut to pass if the observatory breaks down. But it’s worth taking the risk for the views.

The Lagrange points have already been used in other missions, not just those that form between the Earth and the Sun. For example, NASA has just sent a probe, Lucy, to explore the Trojan asteroids that surround Jupiter. These asteroids inhabit the Lagrange point between Jupiter and the Sun.

Regarding Lagrange points in the Earth-Sun system, Sun observers as fruitful as SOHO were placed at L1. At L2 there are already several satellites, including the Wilkinson spacecraft and the Herschel and Planck space observatories. So James Webb will have to make room.

A point-to-point interspace journey

One of the real features of the Lagrange points that give the fiction more space is that the special properties of gravity make it remarkably easy for the spacecraft to move from one Lagrange point to another, pushing with minimal thrust. If we could establish habitable bases at the Lagrange points, moving from one to the other would be much easier than going up and down to the moon.

Hypothetically, a space agency could move James Webb from distant L2 to a much closer Lagrange point created by the Earth and Moon, which would be easier for astronauts to reach. At that point in Lagrange, a workshop could be established to attend to future missions and send them back to L2.

NASA had used these routes before: in the early 2000s, a spacecraft traveled In L1, between the Earth and the Sun, it picked up some particles from the solar wind and slid to L2, where it remained until fulfilling its destiny, falling in the Utah desert.

Location of the James Webb Space Telescope in relation to the Hubble Telescope’s orbit around the Earth. Credit: NASA

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