The James Webb is the most powerful space telescope ever built. It was conceived over 30 years ago to be the successor to Hubble, offering a significant increase in infrared resolution and sensitivity over its predecessor.
Its main mirror is composed of 18 hexagonal cells that together form a large golden mirror 6 and a half meters in diameter, a catchment area about 6 times larger than Hubble's.
Unlike Hubble, James Webb's optics do not favor the observation of visible light. Although it sees some orange and red, it is designed to operate in infrared. That's why your mirrors are coated with gold, because gold better reflects the infrared spectrum.
In infrared, James Webb will be able to see star formation inside dust clouds, analyze the composition of the atmosphere of exoplanets and observe space even deeper than Hubble, recording the formation of the universe's first galaxies, just a few million years after the Big Bang.
But to make observations in the infrared spectrum, the James Webb Space Telescope will need to work at a temperature below -220°C. Otherwise, the heat from the telescope could overwhelm your instruments. So, in addition to a powerful cooling system, it will also have a 5-layer solar shield, the size of a tennis court, designed to block the light and heat from the Sun, Earth and Moon.
This will only be possible because the James Webb will operate close to the Lagrange L2 point, which is about 1.5 million kilometers from Earth, in the opposite direction from the Sun. The L2 point is a stable region of space, where the summation of the Sun's and Earth's gravities, allow an object to remain in the Sun's orbit in a position synchronized with the Earth. In this position, your shield is able to shield the telescope from light and heat from the Sun, Earth and Moon at the same time, because they are both in approximately the same direction.
The only problem is that in this region of the space there are no workshops close by and you can't even tow the equipment if it needs any maintenance. That's why the James Webb has been built with strict quality control and its systems have been tested to exhaustion. The last tests were successfully completed in California, and it is now ready to be sent into space.
It will be launched from the base in Kourou, French Guiana, in an Ariane 5 rocket, considered one of the most reliable launch vehicles. If all goes well at launch, James Webb will embark on a two-week trip to the point of Lagrange L2. Along this path, it will be carefully deployed and, before starting its scientific operations, its optics will be aligned and its instruments calibrated, which should take a few more months.
Since 1997, the space telescope project has undergone two major revisions, its launch has been delayed by 14 years and its budget has gone from 500 million to more than 10 billion dollars. But it looks like it's going to be worth every day of waiting and every extra dollar invested in the James Webb, humanity's most powerful space telescope.
Digital Look
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1- James Webb Space Telescope Components. Source: NASA
2- Scale comparison between the James Webb (left) and Hubble (right) telescopes. Credits: GSFC
3- Carina Nebula recorded by Hubble. On the left, in the visible spectrum and on the right, in the infrared, where you can see the stars forming behind the dust clouds. Credits: NASA / HST
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