We see something when the light coming from that object falls on our eyes. However, there is a limit to the speed of light. The speed at which light travels in a vacuum is about 299,792.458 kilometers per second. That is, if we look at an object at a distance of 299,792.458 km, we see the light that came from it a second ago. It takes about 8 minutes for light from the sun to reach the earth. That is, we always see the sun that was about 8 minutes before the moment we watched.
In this way, when we look at distant objects, we see light rays emitted from that object in the past. This is why a unit has been introduced to measure distance by the speed of light. It’s light years. A light year is the distance that light travels in a year at a speed of 299,792.458 kilometers per second. A light year is about nine and 12 points (9.461 × 10¹² km).
The nearest star to our solar system, Proxima Centauri, is 4.243 light-years away. That is, we see the Proxima Century star 4.423 years ago. The distance to the Andromeda galaxy is 2.5 million light-years. That is, we see the Andromeda galaxy 2.5 million years ago. In this way, if we observe more distant objects, we will be able to see more of the past. Scientists have discovered that the universe is about 13.8 billion years old.
That is, 13.8 billion years after the Big Bang. That means if we can somehow see 13.8 billion light-years away, we should be able to see the Big Bang. Although not 13.8 billion light-years away, close-ups should be able to see the first formation of stars and galaxies in the universe.
So scientists have been dreaming about this for a long time. Their dream is only a few months away from becoming a reality. The “James Webb Space Telescope”, the result of the “Next Generation Space Telescope” project, launched in 1996, is currently being prepared for launch.
In the 1980s and 1990s, NASA launched four space telescopes, the Compton, the Moon, the Hubble and the Spitzer. This program, called the Great Observatories, provided much information about the universe. So the next-generation space telescope project to launch another advanced telescope began in 1996. The Canadian Space Agency (CSA) and the European Space Agency (ESA) joined NASA in the project, and TRW won the contract to build the telescope.
The company was later acquired by Northrop Grumman and the project was continued by Northrop Grumman. The project is being managed by NASA’s Goddard Space Center, which also manufactures scientific instruments such as cameras attached to telescopes. Ball Aerospace Technologies manufactures the “telescope part” of the space telescope, and Northrop Grumman is responsible for designing and finalizing the frame of the telescope.
The most important part of a telescope is its primary mirror. This mirror system focuses light from the universe on telescope observers. The primary mirror in the Hubble Space Telescope is about 2.4 meters in diameter. The primary mirror of the James Webb telescope is about 6.5 meters. It is made of 18 gold-plated hexagonal parts made of beryllium.
It has an area of 25.4 m² to collect light. If it were made as a single mirror, it would not be able to be carried on any of the existing rockets, so it is designed as a mirror that can be folded into three parts. In addition, there are two secondary and three-dimensional mirrors to direct the light rays to the observers. It has 126 motors to turn each mirror so that it faces in the right direction.
The purpose of the Web Space Telescope is to study the first stars and galaxies in the universe that formed after the Big Bang. To observe the universe at its initial stage, one must look in the infrared region. This is the reason. After the Big Bang, the universe expanded so rapidly that all the electromagnetic waves, including the light emitted at that time, expanded. That is, the wavelength of all the waves increased. Therefore, the wavelength of the light rays emitted at that time has expanded to the infrared region.
Therefore, the James Webb Telescope, which observes the ancient universe, observes the region from orange to medium infrared waves (0.6 to 28.3 μm). But observing infrared waves is a very difficult task. This is because every object that has a temperature emits infrared rays. If the telescope’s mirror is maintained at room temperature, the infrared rays emitted by its temperature will mix with the infrared rays reflected by the mirrors and distort the star’s information. Therefore, telescopic mirrors and scientific instruments need to be cooled to minimize the amount of infrared light emitted.
It uses a 5 layer sun shield made of Kapton, as thick as a human hair. As large as 14 × 20 m, this cover can be compressed to a very small size for handling in a rocket when launched. This sunscreen blocks sunlight and keeps the telescope’s mirrors and observation equipment at a freezing temperature of -220 C.
The James Webb Telescope will operate in an orbit called the Sun-Earth L2 Halo Orbit. This is an orbit that not many people have heard of. When an object is moved 1.5 million kilometers away from the Sun from the Earth, it leaves the Earth’s gravitational field and enters a solar orbit. But on top of this the Earth’s gravity is still activating. This works in the same direction as the Sun’s gravitational pull. That is, the two gravitational forces of the Sun and the Earth combine to act on this object.
This increases the total gravitational force acting on it. Therefore, even if the object is farther away from the Sun than the Earth, the gravitational force exerted on it will increase. Therefore the orbital velocity here increases. In other words, the time it takes for an object to orbit the sun now is less than the time it takes for an object to orbit the sun alone at this location.
If this were 1.5 million kilometers away from the Sun, the time it would take for the object to orbit the Sun would be the same as the time it takes for the Earth to orbit the Sun. That is, the object is constantly at the line connecting the Earth and the Sun. This location is known as the second Lagrange point or Sun-Earth L2 point in the solar system.
However, this point is dynamically unstable. That is, if an object is pushed away from a fixed position, it will continue to move away. Because of this, the objects at this point are actually moving up or down or around that point instead of being fixed in one place. Although these are called orbits, they are a different type of orbit than normal orbits. In a normal orbit, an object moves around another object. But in these orbits, objects move around the lagrange point. Here James Webb points the telescope to an orbit called the Halo Orbit. There, the telescope will orbit around a point around Sun-Earth L2.
While in this orbit, the telescope is always exposed to sunlight. However, the sun’s cover blocks light from the earth and the sun on the same side, allowing the telescope’s mirror to cool to the required level and make infrared observations. There are solar panels and other equipment on the side facing the sun.
The James Webb Telescope is 1.5 million kilometers from Earth, so if something goes wrong, it will not be possible to repair it. So this telescope needs to be perfectly built and launched. The James Webb telescope, launched by Airanespace’s Ariane 5 rocket from the Kourou Space Center in French Guiana on December 18, will return to its orbit in about a month. During that time, the folded parts, including the sun visor and the primary mirror, will expand one by one.
