Sanuj Raj
6 min readJan 17, 2021


JWST vs The Hubble


James Webb in its basic form is an orbiting infrared observatory that will investigate the thermal radiation of space objects. It is specifically made to answer the fundamental question of where it all started, how the Big Bang created the universe?

Fundamentally JWST (James Webb Space Telescope) is considered as the successor of the legendary Hubble which was launched in 1990 but just like the Hubble, it represents the peak capability of humans at that particular moment in time. It is a monumental challenge to launch this thing as a lot of capital is at stake and there is no margin for error and more importantly, almost 30 years have passed and we haven’t gotten a true successor, so the most valuable asset time, is also on the line.

The true Scale of JWST

Recently, the JWST has passed most of its rigorous testing which ensures its safety during lift-off. The launch is scheduled for 31st October after a continuous 13 years of delay.
Let’s cross our fingers and hope that this time the launch happens.

Why do we need to have a Telescope in Space?

In simple terms, we need telescopes in space because of the clarity that they provide for taking superior-high-quality images which can’t be achieved by any telescope on the ground irrespective of the ability. If we try to capture images of the distant galaxies, the visible rays coming from infinity are distorted by the thick atmosphere and somewhat tends to be misleading, the incoming rays get scrambled between the air molecules and produce unclear images.

People over a thousand years have wondered to solve this problem but they have failed miserably but now this problem is kind of solvable as some new breakthrough technologies have made it possible to do so.
A new technique has been developed in which a beam of the laser is projected into the atmosphere from where the rays are arriving and the beam makes up for the distortion that there is and clears the sky for any aberration. This allows for good and accurate images to be captured.


James Webb is the next chapter after the Hubble in the astronomy world, the telescope is named after James E. Webb, NASA’s second administrator. It was initially scheduled to launch in the year 2012 but it is currently scheduled on 31st October 2021. There have been several launch delays prior to this launch date, it is in our best interest to hope that we get to see the telescope launch on 31st. It is NASA’s most ambitious and complex astronomical project yet.

JWST has the largest primary mirror ever to be flown in space at 6.5 meters wide, it is more than 6 times the Hubble Telescope’s primary mirror.

Overprized for a Reason:-

Due to several delays NASA, many a time decided to pull out of the project but they chose to stay as they invested heavily to make this a reality, sure the project has been many folds overprized but it will be a stupid idea not to go ahead with the launch.
Part of the reason it is overpriced because it is not meeting the standards set by NASA as unlike Hubble which was visited by astronauts several times, James Webb couldn't be accessible at all because it is going beyond the LEO (Low Earth Orbit), the farthest any human has ever been.
Everything should work in the first go, and there is no margin for error. If a mistake were to happen, the project has to be discarded or the scientists have to make the best out of it.

The outer surface of the primary mirror is covered with a very thin layer of gold consisting of only 3 grams. No wonder the surface appears to be shiny bright gold color.


1.The JWST is made up of a special type of metal called Beryllium. The outside coating is done by this metal. It mainly used for its high strength to weight ratio and is good at holding its shape across a range of temperatures which can be as low as -240°C. The property of the metal will allow the telescope to see deeper into the universe than ever before.
There are 18 Beryllium regular hexagonal panels to be precise.

Periodic Properties of the Beryllium metal and Mirror Itself

2. The visible light when traveling for billions of years tends to have a shift in the wavelength towards the red color which is referred to as “Red Shift”. The more a galaxy appears red in color the older it is and the farther it is. This is exactly what the telescope is looking for, the oldest galaxies of the universe formed just after the Big Bang.
All objects emit radiation in the infrared spectrum which remains in the pure form and doesn’t change much according to the surrounding, that is why JWST captures images in the infrared spectrum.

Range of Light

3. All the instruments have to work in super cold temperatures because it allows for little to no vibrations at the atomic level. As a matter of fact, any matter that has any heat will vibrate and when you are trying to capture light from the distant galaxies that are billions of light-years away then any minuscule vibrate becomes your enemy and you have to avoid it. That is why the JWST revolves around the SUN and not the earth to maintain super cold temperatures in the emptiness of space.

These temperatures are achieved by blocking the incoming rays of the Sun, which is done by the 5 layered Sun shield that is attached to the telescope. For reference, this is the largest Sun shield ever flown. The temperatures that we are talking about here is colder than the surface temperature of Pluto.

Time-lapse of the Sun Shield of the JWST


  1. Unlike the Hubble, it is not in Low Earth Orbit, it is at a distance of about 340k km to 1.5 million km in the opposite direction of the Sun to maintain a super low temperature.
  2. It is too large to fit in the cargo spacecraft, so it is folded like origami so that it can be housed in a 5-meter diameter fairing.
  3. JWST will revolve around the Sun and not the earth, unlike Hubble which revolves around the earth at an altitude of just 570 km. However, James Webb will move in sync with the earth to maintain strong communication. So visiting and repairing the telescope in the event of any failure is not possible. These communications are achieved by NASA’s deep space network which allows for the receiving of signals from every part of space. The antennas are located in every part of the globe which can make a strong communication with the object.
  4. Despite it being more advanced and good at doing its job, it is very light in weight, weighing only 6.2 tonnes compared to Hubble’s 11 tonnes.
  5. Unlike the Hubble, the JWST has multiple mirrors that are stacked together to form a giant primary mirror. Each individual mirrors are hexagonal in shape along with the overall structure. The Hubble had a perfectly round single primary mirror.




Sanuj Raj