We needed a successor that could work for a long time and provide information deep inside the primordial fog...

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James Webb Space Telescope

James Webb Space Telescope (From Google Images) 

Some 300 million years after the Big Bang or 13.5 billion years ago, the remaining gas of the eruption created a dense primordial fog that spanned the entire, early universe. This fog allowed no light inside it to ever escape. Unfortunately for the Hubble Space Telescope, the rise of star formation started during this point. Hubble was an optical light telescope that could only capture optical light wavelengths blocked by the primordial fog.

Hubble only could see 13.2 billion light-years or 800 million years after the Big Bang. Hubble was declared dead in 2020. So we needed a successor that could work for a long and provide information deep inside the primordial fog.

Developed for 15 years and costing about $10 billion, The James Webb Space Telescope was finally launched on 25 December 2021. 

The James Webb Space Telescope is an infrared telescope. Infrared radiations capture heat. This was developed so because stars when formed exert a giant nova that is made of heat (Refer to post Star Life). And the primordial fog of the remaining gas from the Big Bang could not block infrared. Webb could see to 13.5 billion light-years or 300 million years after the Big Bang.

The orbit of JWST - Lagrange Point 2

Lagrange Points (From Google Images)

The James Webb Space Telescope is sent to a unique position in space - The Lagrange Point 2.

The Lagrange Points are points in space where the nearby bodies' gravity makes any object stable in its orbit.

L1 is between the sun and Earth. This place is used for sun-observatory satellites. However, Webb is launched to find the trickles of heat from the faraway depths of space. Meanwhile, the sun is dumping tons of heat into space. Hence, Webb is sent to the far shadows of L2.

Webb's Sun Shield

However, the heat released by the sun, earth and moon could stop Webb's sensors from functioning correctly. Hence, Webb will carry a tennis court-sized (24 x 8 m in diameter) sun shield. The material used is Kapton, a plastic type which is excellent for solar sails in space environments. To increase the thickness of the sun shield, layers of other materials are added to Kapton.

Webb's sensors need to be in supercold temperatures (7 deg. Kelvin or -267 deg. Celsius) to find the heat released by galaxies. The sun shield used would be 5 layers thick. In space, convection (the process of heat transfer by physical movement of bodies.) is not present since there is no air. But the sun's heat and the neighbouring bodies' heat are sent using Radiation (the process of heat transfer using electromagnetic waves; infrared rays). 

To tackle this problem, the layers of the sun shield are designed in such a way, that the infrared waves are sent out back into space. The outermost layer is coated with silicon to reflect most of the rays. Sunlight striking the silicon causes the layer to turn pink. Because of the spacing between each layer, conduction (the process of heat transfer by direct contact of bodies) is not a problem either. Hence, Webb's shield is doing its job well!

Webb's Primary Mirror

Let's now talk about Webb's primary mirror.

The primary mirror has 18 hexagonal mirror segments, each of them having a diameter of 1.32 meters. These segments are inclined at such an angle that, the light (and also heat) will be deflected to the secondary mirror that has a diameter of 0.74 meters which reflects the light to the passageway located In the middle of the primary mirror, which sends the waves to the sensors for analysing.

Webb's mirror is made of Beryllium which is chosen because it is a light metal and is strong for its weight. It can hold its shape in cold temperatures.

The Beryllium segments are coated with a thin layer of gold which is an excellent reflector of infrared. Hence this material.

Challenges Tackled

Webb is too large to fit in any rocket fairing. Hence, it is folded using lots of motors controlled by human-operated systems. It is shipped into the 5-meter-long diameter of the fairing of ESA (European Space Agency)'s Ariane 5 rocket. 

Webb cannot be serviced by astronauts. Hubble orbited till 2020 at a height of 547 km from the Earth's surface. But Webb is orbiting at Lagrange Point 2 which is nearly 4 times the Lunar Distance. This is too far away for any human to travel. Hence, if there is any flaw detected in the unfolding process, the entire mission is demolished. Also as Webb's sun shield is folded like a parachute, we would only know if this shape is proper at the unloading phase. But now Webb is perfectly unfolded and doing its job. Webb has a lot of motors behind the shield, mirror and other components. These are directed by systems on Earth to lock the pieces into their respective places.

Also, the chances of Webb getting struck by micrometeoroids orbiting the sun are high. Webb is already prepared and tested for its strength in surviving the impact on the ground before its launch. But recently, a huge meteorite struck one of Webb's segments of the Primary mirror which is bigger than the largest objects tested on Earth. But astronomers after research have concluded that this damage wouldn't have much effect.

Outro

Till now, Webb has clicked many images that can be found in Google Images or news articles. These pictures look brighter and crisper than Hubble's version of the same pics as the Carina Nebula. Webb is the next generation of research that fulfils the curiosity of humans to know more about the universe.

In the post Extraterrestrial Life, I mentioned the planet Proxima Centauri B as a possibility of hosting Alien life as it has an ESI (Earth Similarity Index) of 8.1. Webb is also designed to find the answer to this question. When the time comes, we shall know whether we are alone in the universe or not.

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Thank you for reading.

Aditya VN Kadiyala