Its design began in 1996 as a “Next Generation Telescope” and plans for launch had been in place since 2007, with a budget of one billion US dollars. James Webb was the second appointed administrator of NASA.
JWST has a primary mirror that consists of 18 separate sections, or “panels,” which combine to create the overall mirror’s photodetector. This arrangement allows JWST to have a large mirror with a mirror diameter of about 6.5 meters. This mirror allows light to be collected and focused for JWST’s space observations.
JWST's primary focus is on the infrared (0.6–28.3 mm) because it can see through clouds of dust and gas, giving it sharper images of objects and better resolution of distant objects. This allows it to study the first galaxies, star formation, and the detection of distant exoplanets. The telescope's ability to see in infrared light allows it to see things that the human eye cannot, and it also allows it to see thermographically through interstellar dust, allowing astronomers to look back in time further than ever before, to when the first stars and galaxies formed 13.7 billion years ago, something that was impossible for previous ground-based and space-based instruments. Another goal of the mission is to understand the formation of stars and planets, which includes directly imaging exoplanets, while it will search for signs of extraterrestrial life.
The new space telescope, much larger and more powerful than any of its predecessors, aims to advance astronomical observation from space beyond what its predecessors have achieved. The WTD is designed to fill a gap in astronomical observation without the obstacles of Earth’s atmosphere, specifically to observe the sky in the near and mid-infrared part of the spectrum. Because the most distant celestial bodies are seen with their radiation shifted toward the red, they emit light with more near-infrared radiation and can only be observed with telescopes that detect it. In addition, infrared radiation can penetrate clouds of dust and gas, revealing what lies within and behind them.
The 6.5-ton “Webb” is sensitive to very faint celestial bodies compared to the “Hubble”. In addition, it has a larger field of view, covering 15 times more of the sky. The primary mirror of the DTTG consists of 18 hexagonal sections, which unfold and adjust to form a mirror with a diameter of 6.5 meters, after launch. The mirrors are made of the very light chemical element beryllium and coated with gold, which reflects infrared light very well. The gold is responsible for their yellow color. The largest component of the DTTG is the five-layer solar shield, which reduces the solar radiation reaching the telescope by a million times and is the main reason for its large size (20 by 14 meters). At L2, on the side facing the Sun, the shield will have a temperature of 85 oC and on the other side, from where the telescope will make astronomical observations, it will have -233 oC!
Space Series E8: Το διαστημικό τηλεσκόπιο James Webb
JWST-Webb orbits the Sun at a distance of 1.5 million kilometers from Earth, at a point called the second Lagrangian point, or L2, which it will reach a month after launch. At the Lagrangian points, the gravitational pull of the Earth and the Sun is balanced by centrifugal force, so objects there can remain stable. Specifically, the L1, L2, and L3 points are unstable and require regular correction by firing course correction nozzles, but with little fuel consumption. At L2, JWST-Webb's solar shield will block both light from the Sun and light reflected from the Earth and Moon. This keeps the Webb cold, a necessary condition for an infrared telescope (radiated heat is infrared rays, which would distort the infrared signal sent by celestial bodies observed by the telescope). As the Earth orbits the Sun, the Webb will orbit with it, but remain at the same distance from the Earth and the Sun.
Among the scientific goals of "Webb" are the observation of the most distant galaxies, in order to form a better picture of the evolution of the visible universe in relation to the dominant theories that describe it, the role of supermassive black holes in the formation or evolution of galaxies. It will also make observations on the formation of stars and new planetary systems, astronomical phenomena that occur in dense clouds and are therefore rarely visible. Scientists expect the discovery of many exoplanets from "Webb". Its particular target will be brown dwarfs, celestial bodies between stars and planets, with characteristics of both, radiating mainly in the infrared.
The atmospheres of the planets of the solar system and their satellites that have atmospheres, as well as the atmospheres of the closest exoplanets that have been discovered, will be the subject of careful study by the new telescope, as the spectrometers of the WTTG will be able to analyze the light of the stars that passes through them, in order to identify the spectral signature of the chemical elements that form them. Even the rings of Saturn, Neptune, Uranus and Jupiter are much better visible in the infrared. The rings of Saturn in particular have been shown to be a system of destruction and reconstruction of satellites from the materials of previous moons, and the "Web" will show whether the same happens with the rings of other planets.
It will also make observations of Jupiter and its moons, Ganymede and Europa with possible oceans beneath the icy surface, Io with its "hidden volcanoes" of sulfur, the other outer planets and Saturn's moon Titan, which is the only other body in the solar system besides Earth that has liquid lakes and seas (even if they are not made of water).
JWST's complementary observations on the findings of the Spitzer infrared space telescope will provide more evidence regarding the discovery of water vapor in at least half of the protoplanetary nebulae known to date, providing some answers about the origin of water on Earth.
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