Later this year, the James Webb Telescope will be launched into space. With its large gold-coated mirror and infrared capability, the telescope will examine the formation of the first galaxies.
The universe is thought to be about 13.8 billion years old, and the James Webb Telescope (Webb) was built to see the birth of the first stars and galaxies.
Looking back in time, Webb will measure light from distant celestial bodies in the universe. Light travels at a speed of about 300,000 kilometers per second, but the light to be examined comes from celestial bodies so distant that it was still being sent for several billion years.
As the universe expands, the light moving in the universe is pulled out and has a longer wavelength. And if a celestial body moves away from the Earth at the same time as it is radiating toward us, then the wavelengths are being pulled out as well.
This means that the light webb should be measured toward and within the infrared portion of the electromagnetic spectrum, it becomes Redshift. So the web is primarily built to observe infrared light and has a sensitivity of wavelengths between 600-28500nm.
The cold side is directed towards the universe
The sun, earth, moon and even the telescope itself can create background noise in the measurements because the thermal radiation from these measurements is present in the infrared. So Webb has a great heat shield 300 square meters It is protection from thermal radiation. It consists of five layers, as thick as plastic sheets, separated from each other to avoid the transfer of heat from one layer to another.
The Webb Heat Shield gives a warm and cool side. The warm side, always facing the sun, should maintain a temperature of around 85 ° C. Here you will find, among other things, a computer, antennas, and a satellite controller.
The cold side, shielded from the sun and directed at the universe, should maintain a temperature of about -233 degrees Celsius. On the cold side, detectors and scientific instruments are available, including the large gold-plated 6.5-meter mirror that will collect light.
The main mirror It consists of 18 hexagonal gold-plated sub-mirrors made of beryllium. The concave mirror measures 25.4 square meters and can be folded together for easy portability to space. The telescope also has a secondary and a tertiary curved mirror to reduce imaging errors.
The Web Telescope completes Hubble’s research
Unlike Webb, Hubble mainly measures visible and ultraviolet wavelengths. The infrared capability gives Webb an opportunity to look back in time and see new phenomena that Hubble could not notice. The Hubble Telescope orbits Earth at a distance of 570 kilometers, which is what allows the astronauts to do so Servant Telescope several times since its launch in 1990.
Webb will be transported 1.5 million km and will be traded around another storage range point (L2). L2 is one of the five points where gravity from the Earth and the Sun take each other. This means that smaller objects, such as Webb, can have the same orbital period around the sun as the Earth. This also means that Webb and the Earth will be relatively constant with respect to each other, and the telescope can then look at the universe with the heat shield facing the interior constantly toward the sun and the earth.
One of the 18 sub-mirrors that make up the main mirror. Photo: Drew Noel
Another telescope besides Hubble paved the way for Web it Spitzerteleskopet, Also an infrared telescope orbiting L2. The Spitzer is cooled by liquid helium to avoid background noise and has a sensitivity to a different wavelength range than Webb. The telescope experiments that were discontinued in January 2020 have given an increased understanding of how research is being conducted with infrared telescopes.
Like Spitzer, Webb will study exoplanets and their atmospheres. Use Spectrum Webb will determine the content of planets’ atmospheres. When an exoplanet passes in front of a star, some of the light that reaches the web passes through the planet’s atmosphere. Different materials in the atmosphere absorb light in different wavelengths. By measuring the absorption lines, the wavelengths at which the light intensity is lower, it is possible to determine what the atmosphere contains.
Swedish researcher: “It would be very exciting”
Webb will be launched with an Ariane 5 missile from French Guiana on October 31, 2021, according to the current plan. During launch, the heat shield and mirrors fold out.
It is then revealed in stages on its way to the telescope’s orbit at L2. There are several steps that must work in order for the telescope to end in place and be able to begin collecting data.
Göran Ostlin is Professor of Astronomy at Stockholm University and investigates galaxies. In his research, he relied heavily on images from Hubble, and looked at measurement data from the Web.
– It will be very exciting. The one I’ve used the most so far is Hubble. The Hubble Telescope is great for the micrometer in the wavelength, and Webb will be able to see much longer wavelengths. There is a lot that can happen within these wavelength ranges. The advantage of infrared radiation is that the gas in galaxies becomes more transparent. Göran Ostlin says interstellar dust absorbs less infrared radiation, so it will be easy to see what is happening.
The telescope with the main mirror is folded and the heat shield evolves. Photo: NASA / Chris Jan
It has been many years since construction of the telescope began and the launch has been delayed several times. This does not mean, however, that the technology in the telescope is outdated.
The technology found in James Webb is technology that was available and mature in the early twentieth century. If they had started ten years later, in 2010, they would have chosen other technical solutions. But at the same time, there are many other benefits of being in space, which cannot be compensated from the Earth where the atmosphere is blocked, so a telescope would be very good. When it comes to space, you usually don’t take the latest developments, you want mature technology. It should be “space-qualified,” that is, it underwent several tests in a space environment, says Göran Ostlin.
What do you think will be the most we learn from the James Webb measurements?
Maybe something we didn’t expect before. These are the experiences we have from previous telescopes. We have some ideas of what we should be able to do with Webb, but the big driving force is that you should be able to look further than any other telescope, says Göran Ostlin.
Lagrange Points / Web Orbit
There are points in space where the gravitational pull of the sun and the earth takes on each other. A smaller object, such as a satellite, placed in orbit around one of these points could maintain the relative position of both the sun and the Earth. These points are called storage ranges.
There are five storage ranges. Points are solutions to the finite three-body problem and are named after Joseph Louis Lagrange, who found the last two points in the 18th century.
Webb will be transported 1.5 million km to the second storage range point (L2). In L2, Webb will follow the Earth’s orbit around the Sun. The grid and the Earth will be fixed relative to each other, which means that the telescope can look at the universe with the heat shield facing inward toward the sun and the earth.
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