James Webb Space Telescope the Time Machine To The Past. #NASA @starspace

 JAMES WEBB SPACE TELESCOPE  

James Webb space telescope (Also known as JWST) is a reflector telescope that was launched into space with a 6.5 m giant mirror. It can detect majorly near Infrared and middle infrared wavelengths of light to be precise about 600 nm to 28,500 nm coming from outer space.

This is an International Collaborative project between the NASA(National Aeronautics and Space Administration), ESA (European Space Agency) and CSA (Canadian Space Agency) which at an approximate costed them 10 billion Dollars to build it.   

This Telescope was sent into the space on 25 th December 2021 towards Lagrange Point 2 By the European Space Agency's Ariane 5 Rocket, A heavy lifter which had enough space inside its Payload fairings to fit the James Webb Space Telescope.  

       

Ariane 5 rocket   credits :ESA 

                 Official launch of JWST               

The setup of the Whole Telescope 

credits: NASA 

The satellite can be divided into 2 parts one below the sunshield and one above it.  

 Above the sunshield is the region facing away from the sun, here temperature is kept as low as possible to capture the Infrared spectrum of the part of the universe the telescope is observing. This part includes 18 mirror segments which together form the primary mirror, the secondary mirror, and all the instruments.    

Sunshield 

This sunshield includes 5 layered sheets of that helps in reflecting all infrared waves (Heat) from the sun and other planets this system includes many moving parts which makes the complete process of deployment to critical.  

Along with the shielding system an array of radiator behind the mirrors to radiate out heat produced by various operating devices and to further cool the instruments. 

The mirror  

 The Primary mirror is made up of 18 Hexagonal Gold-plated Beryllium panels which will be focusing light on to the secondary mirror, secondary mirror will reflect the light towards the instruments.  

 

The Integrated Science Instrument Module (ISIM) has these instruments: 

• Mid-Infrared Instrument (MIRI) 

• Near-Infrared Spectrograph (NIRSpec) 

• Near-Infrared Camera (NIRCam) 

• Fine Guidance Sensor/ Near InfraRed Imager and Slitless Spectrograph (FGS-NIRISS) 

And will all this will result in a clear image of the part of space being observed. 

Below the sunshield is the sun facing side and this part has various instruments such as:  

Momentum trim Flaps help in balancing the solar pressure on the sunshield.   

Solar arrays face the sun to capture solar energy and convert it into electrical energy. 

Earth Pointing Antenna is used to send various science data towards the Earth and receive the commands from NASA’s Deep Space Network of radio telescope. 

A small telescope known as the Star Tracker uses the star pattern to orient and target the observatory(here observatory comprises of optical telescope, instruments, the sunshield, and spacecraft bus).  

 

Deployment of the telescope

Deployment of the telescope 

Why is the telescope sun-shielded ? 

The telescope is shielded because the telescope requires very less temperature to run properly since it needs to capture and detect the weak infrared waves coming from extremely far in the observable universe and not the strong infrared waves from the earth moon and mainly the sun.  

Its cooling instruments can bring temperature below 50 Kelvins enough to make almost any gas solid this temperature is very close to Absolute Zero (0 Kelvin) 

Absolute Zero is that temperature in kelvin scale at which an Ideal Gas (Hypothetical gas) would have a negligible volume. 

Kapton - A material used to make the shield sunshield  

Kapton is a material of high-performance plastic that can manage extreme temperatures like –286°C and 400°C used to make 5-layer kite shaped sun protection shield as thin as a human hair, it serves as a guard protecting the telescope from sun's heat (infrared waves emitted by sun).

These layers are coated with reflective metal to reflect the suns heat. 

All the 5-layers are coated with Aluminum and the first 2 layers facing the sun are treated with silicon. 

Why is JWST focusing mainly on the infrared and very little part of the visible light? And how is it able to see in Past?  

The main reason is that when focusing on objects extremely far away from the telescope itself that is when we are viewing objects millions of billions of light years away or in other words the light is so old that the time it was emitted it was way back in the past.
 [for instance 1 light year is the time taken by a photon of light travelling at 3×10^8 m/sec which is equivalent to about 9.46 trillion kilometers].
  This light has now red shifted just like sun light gets reddish during evenings and early mornings since light spectrum with larger wavelengths are not easily absorbed.  

Why is gold electroplated on the mirrors of the telescope?  

The mirrors of the JWST are gold plated and this is done to ensure the highest reflection of infrared light towards the instruments on it also each plate is made of beryllium then electroplated with gold such that the telescope maintains lesser weight.  
Infact the net weight of this telescope is lesser than that of the Hubble telescope which is known for the images it captures of the deep space in visible light, and small range of UV, Infrared light.

Size comparison between JWST and Hubble telescope

Range of spectrum in which JWST Hubble and Spitzer telescopes captures light

Why are the segments of the mirror hexagonal in shape?  

There are a total of 18 mirrors on the telescope made such that they maintain high filling factor and six-fold symmetry. 

High filling factor means that the segments, can align and fit together without any gaps. This kind of form factor of segmented mirrors ensures a near circular oval shape that focuses the light into the most compact region on the detectors. 

After the launch, the position of the mirror segments will be monitored by a detector named wavefront sensor (NIRCam in this case) measures for imperfections in the alignment of them.  

Through process called wavefront sensing and control corrections to the mirror segments will be made so as to aligns the mirrors to within tens of nanometers. 

This ensures a sharp and focused image.

How nanometer alignments work  

What Is L2 Point? Why Only this point in space was apt for the telescope? 

Lagrange points are positions in space where the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them. These points in space can be utilized by spacecraft to reduce fuel consumption needed to remain in position.

The Lagrange point 2 is a position in alignment of the sun, the Earth and the moon. The benefits of being at this point is that the spacecraft is close enough to readily communicate with the earth shielded by the sun's heat and hence best for deep space observation.  

This point was chosen such that the JWST’s 5-layer shield will always face the Sun blocking all heat to reach the telescopes detectors.  

Deployment of the Telescope full video 

Present Status of JWST  

Official Web site 

Where Is Webb? NASA/Webb: James Webb Space Telescope

Written by: Swapnil Pandit 

Image Courtesy : NASA ESA  

Thankyou!!