Deep space ghosts
Someone once said: the creators of Hubble need to erect a monument in every major city on Earth. He has a lot of merits. For example, with the help of this telescope, astronomers have taken a picture of the very distant galaxy UDFj-39546284. In January 2011, scientists found out that it is located further than the previous record holder - UDFy-38135539 - by about 150 million light years. Galaxy UDFj-39546284 is 13.4 billion light years distant from us. That is, Hubble saw stars that existed more than 13 billion years ago, 380 million years after the Big Bang. These objects are probably not "alive" for a long time: we see only the light of long-dead stars and galaxies.
But for all its merits, the Hubble Space Telescope is the technology of the past millennium: it was launched in 1990. Of course, technology has made great strides over the years. If the Hubble telescope appeared in our time, its capabilities would have surpassed the original version in a colossal way. This is how James Webb came about.
Why "James Webb" is useful
The new telescope, like its ancestor, is also an orbiting infrared observatory. This means that his main task will be to study thermal radiation. Recall that objects heated to a certain temperature emit energy in the infrared spectrum. The wavelength depends on the heating temperature: the higher it is, the shorter the wavelength and the more intense the radiation.
However, there is one conceptual difference between telescopes. Hubble is in low Earth orbit, that is, it orbits the Earth at an altitude of about 570 km. James Webb will be launched into a halo orbit at the L2 Lagrange point of the Sun-Earth system. It will revolve around the Sun, and, unlike the situation with the Hubble, the Earth will not interfere with it. A problem immediately arises: the farther an object is from the Earth, the more difficult it is to contact it, hence the higher the risk of losing it. Therefore, "James Webb" will move around the star in sync with our planet. In this case, the distance of the telescope from the Earth will be 1.5 million km in the opposite direction from the Sun. For comparison, the distance from the Earth to the Moon is 384,403 km. That is, if the James Webb equipment fails, it will most likely fail to be repaired (except remotely, which imposes serious technical limitations). Therefore, a promising telescope is made not only reliable, but super reliable. This is partly due to the constant postponement of the launch date.
James Webb has another important difference. The equipment will allow him to concentrate on very ancient and cold objects that Hubble could not see. This way we will find out when and where the first stars, quasars, galaxies, clusters and superclusters of galaxies appeared.
The most interesting finds that the new telescope can make are exoplanets. To be more precise, we are talking about determining their density, which will allow us to understand what type of object is in front of us and whether such a planet can be potentially habitable. With the help of James Webb, scientists also hope to collect data on the masses and diameters of distant planets, and this will open up new data about the home galaxy.
The equipment of the telescope will allow detecting cold exoplanets with surface temperatures up to 27 ° C (the average temperature on the surface of our planet is 15 ° C)."James Webb" will be able to find such objects located at a distance of more than 12 astronomical units (that is, the distance from the Earth to the Sun) from their stars and distant from the Earth at a distance of up to 15 light years. Serious plans concern the atmosphere of the planets. The Spitzer and Hubble telescopes were able to collect information about about a hundred gas envelopes. According to experts, the new telescope will be able to explore at least three hundred atmospheres of different exoplanets.
A separate point is the search for hypothetical type III stellar populations, which should make up the first generation of stars that appeared after the Big Bang. According to scientists, these are very heavy luminaries with a short lifetime, which, of course, no longer exist. These objects had a large mass due to the lack of carbon required for the classic thermonuclear reaction, in which heavy hydrogen is converted into light helium, and excess mass is converted into energy. In addition to all this, the new telescope will be able to study in detail previously unexplored places where stars are born, which is also very important for astronomy.
- Search and study of the most ancient galaxies;
- Search for earth-like exoplanets;
- Detection of stellar populations of the third type;
- Exploration of the "star cradles"
Design features
The device was developed by two American companies - Northrop Grumman and Bell Aerospace. James Webb Space Telescope is a masterpiece of engineering. The new telescope weighs 6, 2 tons - for comparison, the Hubble has a mass of 11 tons. But if the old telescope can be compared in size to a truck, then the new one is comparable to a tennis court. Its length reaches 20 m, and its height is the same as that of a three-storey building. The largest part of the James Webb Space Telescope is a huge sun shield. This is the basis of the entire structure, created from a polymer film. On one side it is covered with a thin layer of aluminum, and on the other - metallic silicon.
The sun shield has several layers. The voids between them are filled with vacuum. This is necessary to protect the equipment from "heatstroke". This approach allows you to cool ultrasensitive matrices down to –220 ° C, which is very important when it comes to observing distant objects. The fact is that, despite the perfect sensors, they could not see objects due to other "hot" details of "James Webb".
In the center of the structure is a huge mirror. This is a "superstructure" that is needed to focus beams of light - the mirror straightens them, creating a clear picture. The diameter of the main mirror of the James Webb telescope is 6.5 m. It includes 18 blocks: during the launch of the launch vehicle, these segments will be in a compact form and will open only after the spacecraft has entered orbit. Each segment has six corners to make the best use of the available space. And the rounded shape of the mirror allows for the best focusing of light on the detectors.
For the manufacture of the mirror, beryllium was chosen - a relatively hard metal of light gray color, which, among other things, is characterized by a high cost. Among the advantages of this choice is the fact that beryllium retains its shape even at very low temperatures, which is very important for the correct collection of information.
Scientific Instruments
The review of a promising telescope would be incomplete if we did not focus on its main instruments:
MIRI. This is a mid-infrared device. It includes a camera and a spectrograph. MIRI includes several arrays of arsenic-silicon detectors. Thanks to the sensors of this device, astronomers hope to consider the redshift of distant objects: stars, galaxies and even small comets. Cosmological redshift is called a decrease in radiation frequencies, which is explained by the dynamic distance of sources from each other due to the expansion of the Universe. What is most interesting is that it is not just about fixing this or that remote object, but about obtaining a large amount of data about its properties.
The NIRCam, or near infrared camera, is the main imaging unit of the telescope. NIRCam is a complex of mercury-cadmium-tellurium sensors. The working range of the NIRCam device is 0.6-5 microns. It's hard to even imagine what secrets NIRCam will help to unravel. Scientists, for example, want to use it to create a map of dark matter using the so-called gravitational lensing method, i.e. finding clots of dark matter by their gravitational field, noticeable by the curvature of the trajectory of nearby electromagnetic radiation.
NIRSpec. Without a near-infrared spectrograph, it would be impossible to determine the physical properties of astronomical objects, such as mass or chemical composition. NIRSpec can provide medium resolution spectroscopy in the 1-5 μm wavelength range and low resolution spectroscopy with 0.6-5 μm wavelengths. The device consists of many cells with individual control, which allows you to focus on specific objects, "filtering out" unnecessary radiation.
FGS / NIRISS. This is a pair consisting of a precision aiming sensor and a near infrared imaging device with a slitless spectrograph. Thanks to the precision guidance sensor (FGS), the telescope will be able to focus as accurately as possible, and thanks to NIRISS, scientists intend to conduct the first orbital tests of the telescope, which will give a general idea of its condition. It is also believed that the imaging device will play an important role in the observation of distant planets.
Formally, they intend to operate the telescope for five to ten years. However, as practice shows, this period can be extended indefinitely. And "James Webb" can provide us with much more useful and simply interesting information than anyone could imagine. Moreover, now it is impossible to even imagine what kind of "monster" will replace "James Webb" himself, and what an astronomical amount will cost its construction.
Back in the spring of 2018, the price of the project increased to an unimaginable $ 9.66 billion. For comparison, NASA's annual budget is approximately $ 20 billion, and the Hubble at the time of construction was worth $ 2.5 billion. In other words, James Webb has already gone down in history as the most expensive telescope and one of the most expensive projects in the history of space exploration. Only the lunar program, the International Space Station, the shuttles and the GPS global positioning system cost more. However, “James Webb” has everything ahead: its price may rise even more. And although experts from 17 countries participated in its construction, the lion's share of the funding still rests on the shoulders of the United States. Presumably, this will continue to be so.
