James Webb-The King of Telescopes

 

Image: wikimedia commons

The answers to every question that science discovers create many new questions. In that sense, the James Webb "Space Telescope" is a telescope sent to find answers to all the questions we have about the universe. 

This post explains the structure of the telescope, its orbit, its functions, and the purpose for which it was sent into space.

This space telescope, known as James Web, was constructed by our scientists after 25 years of work and at a cost of nearly 7400 crore rupees. The name James Webb is named after James E. Webb, the second executive director of NASA. 

Before this, the Hubble space telescope was launched into space in 1990 and has been working for more than 30 years. It is capable of photographing visible light, ultraviolet rays, and a small amount of infrared rays. 

But the James Webb telescope can only detect infrared rays. So, it is more powerful than the Hubble telescope. 

The Hubble telescope takes pictures of the dust surrounding the stars and the clouds they create. 

But because the James Webb telescope only photographs infrared light from stars, all the dust particles surrounding the star are filtered out. So, we get a clear photo.

Image: Flickr

The Hubble telescope is about the size of a school bus. But the James telescope is a huge one, about the size of a tennis court. Its area is 70×48 ft2.

The Hubble telescope orbits the Earth at a distance of 547 kilometers above Earth. But the James Webb Telescope orbits the Sun at a distance of 1.5 million kilometers from Earth.

The part called the sun shield at the bottom of James Webb is always facing the sun. 

Even if there is a malfunction in the Hubble telescope, astronauts can be sent to repair it. But we cannot repair the James Webb telescope. because it is four times farther away than the moon. Its lifetime is only 5 to 10 years. But we cannot determine the lifetime of the Hubble telescope while we repair it. 

Construction of the James Webb Telescope began in 1996. And this telescope is scheduled to be launched into space in 2007. At that time, the value of this project was only 3500 crore rupees. The telescope was named in 2003. But in 2005, many changes were made to its structure. Then,in 2016, it was completely constructed. And for this, up to 75,000 crore rupees were spent. Scientists had planned to launch it into space in 2018. But in an intervening test, a thin part of the telescope called the sunshield is torn. So that its launch was delayed. 

It was planned to launch in 2020 after fixing the minor problems. But the project was further postponed due to the Corona virus that hit the world that year. In 2021, when all the tests were completed and it was ready to be launched into space, the launch vehicle was not ready. After overcoming many problems, on December 25, 2021, this telescope launched into space. 

Image: wikimedia commons

On January 24, 2022, the telescope reached the L2 region of space and began its orbit. On July 11 of the same year, it was fully assembled in space and began its explorations.

Structure of James Webb:

The mass of this telescope is 6300 kg. This telescope has three types of mirrors, namely the primary mirror, the secondary mirror, and the tertiary mirror. All three are coated with gold. A total of 48.25 grams of gold has been used for these three glasses. The mirrors are coated with gold to a thickness of only 100 nanometers. The reason for gold plating is that gold is highly reflective. 

Image: Flickr

The diameter of this primary mirror is 21.7 feet. And it is five times larger than the Hubble telescope's primary mirror. And it is made of beryllium.

The construction of these glasses was completed between 2010 and 2012. Here, 18 hexagonal mirrors were attached to construct the primary mirror. Each hexagonal mirror has 4.3 feet of diameter. There is a gap of 150 nanometers between each of these hexagonal mirrors. And these glasses are made without human hands. Its primary mirror is slightly concave, and the secondary mirror is convex.

Another important part of this is the heat protection system called Sunshield. It is made of Kapton material. It is a blanket-like structure. Its thickness is equal to the thickness of our hair. 

The James Webb Telescope takes pictures using infrared technology. All matter above 0 K emits infrared radiation. Therefore, a sun shield is used to prevent the infrared rays emitted by the heat of the sun and the earth from hitting this telescope. This system is arranged in five rows at the bottom of the telescope mirror structure. 

Image: Flickr

The bottom of this sunshield faces the sun. So the temperature of the sunshield at the bottom is more than 100 °C. But the temperature at the top (first row) is maintained at -220 °C. The sunshield was loaded into the aircraft only after it had been folded twelve times. 

Image: wikimedia commons 

At the bottom of this shield, there is a bus-like structure that carries the entire telescope. This is called a spacecraft bus. This controls the overall performance of this telescope. Its weight is 350 kg. This bus system has the instruments for communication with Earth. 

Functions of the James Webb Telescope:

This telescope uses hydrazine and dinitrogen tetroxide as fuel.

To photograph a specific part of space, it is first turned towards that part. Light from stars, galaxies, and nebulae in that region is reflected off by 18 tiny hexagonal mirrors in the telescope's primary mirror. (Here, the 18 mirrors look at that particular area from 18 different angles.) 

This reflected light is concentrated at a single point. Because the primary mirror has a concave structure. Therefore, all the light will be concentrated in one place. Its secondary mirror is located in such a concentrated region. So this secondary mirror now captures 18 different photos into a single image. 

Light focused on this mirror is reflected into the "tertiary mirror" in the center of the primary mirror. From here, this light is sent to a system called the near infrared camera (NIRCam) on the back of the mirror. In this system, the infrared radiation in that reflacted light is extracted, converted into an infrared photo, and sent back to Earth. Those photos are converted to wavelengths that can be sensed by our eyes and published. The James Webb Telescope only takes infrared images. 

Because the infrared rays can penetrate the dust and particles in between. And they can even penetrate clouds.

The human eye can only see the light form of electromagnetic waves with wavelengths between 380 and 750 nanometers. UV rays are those with wavelengths of 100–400 nanometers. But the James Webb telescope can even see infrared patterns of electromagnetic waves with wavelengths ranging from 600 to 27900 nanometers. However, the wavelength of infrared rays ranges from 780 to 1000000 nanometers. 

Ultraviolet rays cannot travel beyond cloud clusters. The Hubble telescope can only photograph ultraviolet rays, light rays, and small amounts of infrared rays with wavelengths of 100–1800 nanometers. Ultraviolet rays and light rays are unable to penetrate clouds. Also, it can only photograph low levels of infrared radiation. 

Because of its greater sensitivity to infrared radiation penetrating cloud clusters, the James Webb Telescope gives images with better quality than the Hubble Telescope. 

Comparison between the images of james webb and hubble 
Image: PICRYL

(In this photo, the James Webb Telescope image is on the left, and the Hubble Telescope image is on the right.)

There is another reason why this infrared technology is used. That's because of the red shift. 

The universe is expanding faster than light. Therefore, every object in the universe is moving away from each other. When light from a star or a galaxy, which may be millions of light-years away, reaches Earth, the light waves emitted from it are stretched as the star is moving away from Earth due to the expansion of the universe. So their wavelength is also increased and converted to the wavelength of infrared radiation. Therefore, the light from the stars that reaches the earth from a great distance reaches it in the form of infrared radiation. This is called a red shift. 

Thus, by photographing infrared radiation, we can see even stars millions of light-years away. That's why the James Webb telescope uses infrared technology.

Now, let us have a look at the objectives for sending this telescope into space. 

Its primary objective is to find the first galaxies that formed after the Big Bang. There are many other purposes as well. They are as follows: 

• Uncovering many unknown mysteries about black holes.
• Storing a lot of information about the origin and end of a star.
• Investigating the types of atoms and molecules in the atmospheres of planets outside the solar system that may orbit some other star. 
• Making research on dark energy. 
• Making studies of quasars that may be at the center of supermassive black holes.

(Quasars are a form of energy that can be ejected from the center of a black hole in large quantities.) 

 Picture of Quasar
Image: wikimedia commons

 
How does James Webb find planets many light years away?
 
By measuring the luminosity of a star, we can find out if there is a planet orbiting it.
 
That is, if the luminosity of a star, as seen from Earth, is low for a certain period of time and then returns to its original level, it means that some object is passing by that star. 

Similarly, if the luminosity of a star keeps decreasing at regular intervals, it means that some object is repeatedly passing by that star. 

 

Such repetition can only be a planet. The time interval between the periodic decrease in the luminosity of the star is requested to be one year on that planet.

 

Small changes in the luminosity of this star cannot be seen with ordinary telescopes. But the James Webb telescope can.

Image: Flickr

In general, a planet's atmosphere absorbs a certain fraction of the infrared radiation from its star. If the planet does not absorb infrared rays, it has no atmosphere. 

 

As we have said before, a planet that has a star decreases the luminosity of the star. Perhaps if the planet had an atmosphere, it would absorb some of the infrared radiation that might have come from the star. 

Therefore, if a star's luminosity decreases with a slight decrease in infrared radiation, it means that the planet passing the star has an atmosphere. 

If the planet had no atmosphere, the star's luminosity would only decrease. There will be no change in the level of those infrared rays.

By examining these infrared rays, it is possible to know what molecules are present in the planet's atmosphere. This is how the James Webb telescope studies a planet orbiting another star.

13 countries are involved in the construction of this telescope. However, the project is led by the United States. 

The James Webb telescope is considered to be the best telescope ever invented by mankind. So there is no mistake in calling it "The King of Telescopes.".

We will cover the telescope's current research and the images it has sent in more detail in the future.