The launch of the James Webb telescope is one of the most important events for world astronomy. It is expected to become the successor to Hubble and, once it starts work, will reveal the secrets of galaxy creation by looking into the distant past of the universe. In addition, James Webb will discuss how Earth-like planets originate and, possibly, whether there is life on the moons of Jupiter and Saturn. The James Webb Space Telescope went into space on an Ariane 5 rocket launched from the Kourou Cosmodrome in French Guiana. It will be put into orbit around the Lagrange point L2 of the Earth-Sun system, which means that it will revolve around the Sun along with the Earth. The path to the target orbit will take about a month, and the mission itself will last from five to ten years.

James Webb is a collaboration of 17 countries led by NASA and has the highest resolution telescopes ever created by humans. Its capabilities will surpass Hubble many times over, and James Webb is often named as its successor. At the same time, the telescope has become the most expensive and complex spacecraft and, possibly, one of the most expensive devices in human history. In total, about $ 10 billion was spent on it, which is many times higher than the initial estimates. The launch date was also postponed many times: initially, in 1997, they wanted to launch the telescope around 2007, in the early 2010s, the launch was already scheduled for 2018, and it is only flying now. The scandal was also related to the choice of the name: in March 2021, an article was published in Scientific American magazine, in which it was called for to rename the telescope, since James Webb, the director of NASA in the 1960s, allegedly helped to persecute homosexuals, but the agency rejected this offer.

The James Webb main mirror is about 6.5 meters in diameter, 2.5 times that of Hubble. It is the area of ​​the collecting surface that primarily determines the resolution of the telescope. The James Webb mirror is assembled from 18 beryllium segments and will be folded during flight - otherwise the telescope would not fit under the rocket fairing. The segments have a hexagonal shape, since it is easy to assemble a relatively round object from the hexagons, and at the same time, they can pave the surface without gaps. In addition, actuators are connected to the segments, which will ensure accurate focusing of the mirror.

The mirror is not made of glass, but beryllium, for two reasons. First, it had to be light, about 10 times lighter than a Hubble mirror per unit area. Second, beryllium has a low coefficient of thermal expansion, which is important because the telescope will operate at cryogenic temperatures.

One of the most noticeable external features of the telescope is the golden color of the mirror. It is indeed coated with a thin layer of gold (48 grams per 25 m2), since this metal has good reflectivity, in particular in the infrared range.

Operation in the mid-infrared range will be one of the main differences between the telescope and Hubble. This means that James Webb devices will be able to detect the thermal radiation of cold (compared to stars) objects: brown dwarfs, planets and gas and dust clouds. And therefore, in order not to interfere, the telescope itself must remain extremely cold. For this, the space observatory will be covered with a heat shield consisting of five layers of Kapton with an aluminum coating, and the first two "hot" layers are additionally protected by silicon.

The size of the screen reaches 21 meters long and 14.5 meters wide, and therefore the heat shield will also be folded during takeoff. The thermos-like design will keep the telescope temperature below 50 Kelvin, while the outer layer of thermal protection can heat up to 383 Kelvin, more than 100 degrees Celsius. Placing the telescope at the L2 point will also allow the screen to be closed simultaneously from the Sun, Earth and Moon, which will always be on the same side. But even this is not enough for the operation of some instruments of the telescope, and therefore the observatory has a supply of helium cooler, which allows reaching temperatures below 7 Kelvin.

James Webb has four scientific instruments: a near-infrared camera, a near-infrared spectrograph, a mid-infrared instrument (which requires additional cooling), and a precision pointing sensor combined with a slitless spectrograph.

Scientist Benjamin Pope of the University of Queensland believes the space observatory will revolutionize astronomy.

“James Webb will surpass any telescope that has ever existed,” says the researcher. “He will see the first stars in the universe, billions of light years away.”

This will allow, in fact, to look into the distant past and check the existing models of the evolution of galaxies and the universe.Such observations are conveniently carried out in the infrared range, since infrared radiation passes better through interstellar dust or molecular clouds where stars are born. At the same time, infrared waves are trapped by water vapor and carbon dioxide in the earth's atmosphere, and it is for this reason that it is so important to place the telescope in space.

James Webb will detect relatively cold exoplanets in distant orbit around stars within 15 light years of Earth. He will even be able to establish the approximate composition of their atmosphere: is there water vapor, carbon dioxide or biosignatures, substances that indicate the presence of life.

The observatory will also investigate protoplanetary disks - disks of dense gas around young stars that form planets. The spectrometer will allow you to determine their chemical composition and even detect nascent rocky planets like Earth and understand what substances will fall on them. This will help scientists build more accurate models of the formation of our planet and at the same time find out how many Earth twins can be in the universe.

The telescope will not ignore the solar system either. For example, it will transmit images of asteroids, comets and minor planets in the Kuiper belt extending beyond the orbit of Neptune, as well as high-quality images of Mars and the gas giants.

But perhaps the most interesting target for James Webb in our system is the so-called water worlds, satellites of the gas giants that have an inland ocean. From Europa, the satellite of Jupiter, and Enceladus, the satellite of Saturn, many kilometers of geysers are beating, and the spectrometer of the observatory will record signs of life in them, or, at least, better understand how this water is suitable for its origin.

James Webb will be operational in about six months after launch, as it will have to set up the optical system and calibrate the scientific instruments. After that, for a start, the telescope will have to execute already selected 286 scientific applications, which will take about six thousand hours.

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