James Webb will operate at -233°C in space

The James Webb telescope will operate at temperatures very close to absolute zero. How could they prove it on Earth?

The theoretical lowest possible temperature, also known as absolute zero, is -273.15°C. When an object reaches this temperature, its internal energy level is as low as possible, its molecules stop moving completely, and it doesn’t gets more cool.

James Webb Observatory, which will be a million and a half kilometers from Earth, will operate at temperatures very close to this absolute zero. It’s ready for your mirror to work at -233°C, the average temperature of Pluto (in case anyone was thinking about choosing this planet to move to). James webb it has to be very cold to be able to pick up extremely weak thermal signals, which it can receive from the first stars and galaxies that formed at the origin of the universe.

The location where the James Webb telescope will be placed allows for an extreme thermal quirk. One part of the telescope receives radiation from the Sun, the other side, however, is always in its shadow.

The temperature difference between one side and the other is so extreme that NASA explains it this way: “The temperature difference between the hot and cold parts of the telescope is huge – you could almost boil water on the hot side and freeze! Nitrogen on the cold side! ” One part is separated from the other by an “umbrella”, a kind of umbrella that constitutes a thermal retaining wall.

The hood of the James Webb telescope is the size of a tennis court and is designed to keep optics and sensors in the shade and out of interference.

But let’s focus on the cold. James Webb will operate at -233°C. How could you prove it works?

Thermal Vacuum Chambers

The operations that James Webb must perform must be compatible with exposure to very cold temperatures, around -233ºC. Since there is no place on Earth at this temperature, scientists used thermal vacuum chambers to recreate this climate and put it to the test.

The tests were carried out in two phases, in two thermal space vacuum chambers. The top image of this report gives an idea of ​​its dimensions.

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Vacuum chambers allow you to recreate different spatial environments, controlling the physical parameters of the system, such as total pressure, gas composition, radiation and also temperature. In other words, inside these vacuum chambers, it is possible to recreate, for example, the climate of Mars, or, in this case, the “climate” of L2, the point where James Webb will remain.

To submit it for testing, you first need to place the instrument in a vacuum, like a tin can. Once reached, the chamber has systems that allow it to be cooled and heated at maximum and minimum temperatures, using gases such as nitrogen and helium.

The chamber is a cylindrical space, about 27 meters in diameter and 40 meters high, and uses liquid nitrogen and helium to lower the temperature and simulate the space environment.

Vacuum pumps achieve this within approximately one billionth of Earth’s normal atmospheric pressure.

To replicate the vacuum of space, you need to drain the chamber’s atmosphere. For this, massive mechanical pumps are used, which are essentially large versions of vacuum cleaners that people use at home. They manage to eliminate the smallest trace of air from the chamber, until reaching approximately one billionth of the normal atmospheric pressure of the Earth.

Once the vacuum is reached, it’s time to play with impossible temperatures. The James Webb telescope was subjected to a wide range of hot and cold temperatures, ranging from -148 degrees Celsius to sweltering 102 degrees Celsius.

After 116 days of thermal torture, James Webb emerged unharmed from the vacuum chamber

This temperature variation ensures that the spacecraft survives the extreme conditions it will actually experience in space. After 116 days of thermal torture, the heart of the James Webb Space Telescope, Integrated Scientific Instrument Module (ISIM) and its sensitive instruments emerged from the vacuum chamber unharmed in October 2014. It was working.

Half of the Webb Observatory, known as the “spacecraft element,” completed this test at the facility of Northrop Grumman, the mission’s main industrial partner. Webb’s other half, consisting of the telescope and scientific instruments, has successfully completed its thermal vacuum tests at NASA’s Johnson Space Center.

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