Why JWST can make a drastic change in the field of Observational Astronomy

   (Image credit: NASA) 

After the recent series of breakdowns and failures of the Hubble space telescope, we are eagerly waiting for the successor of HST. Well, this is not the reason behind the development of James Webb! The idea of a such telescope came even before the launching of Hubble. As the future looked hazy after the Challenger accident, NASA's first director of the Space Telescope Science Institute (STScI) laid the groundwork for the JWST mission. This is still several years before the launch of the Hubble Space Telescope. James Webb Space Telescope finally launched on 25 December 2021, after years of delay and rigorous testing.

But the question is why JWST can revolutionize the field of observational astronomy? What JWST can do that Hubble Space Telescope can't? The answer lies in the functioning properties of and James Webb. Let's start with the second question first.

To answer this, we need to understand how actually Hubble works.

Hubble Space Telescope exploration capabilities dim beyond the borders of far-ultraviolet and optical range. Hubble’s primary capabilities lie in the borders of the ultraviolet and the visible part of the spectrum, it can observe the small portion of the infrared spectrum. It is not enough as we tend to unravel the secrets of the universe, as more distant astronomical objects are more highly red-shifted means light emitted from them will lie in the near-infrared part of the spectrum.

So why observation in the infrared range is so much necessary in astronomy?

Here is an interesting fact almost half of light from the interstellar is either absorbed or absorbed and re-emitted in the form of infrared light. Wavelengths of light contain varying amounts of information and secrets about the universe. The visible light from other stars and planets which are just farming is completely absorbed by dust clouds. Despite this, infrared light penetrates the dust cloud and provides information about the most astonishing and violent phenomenon in the universe, like the birth of stars.

James Webb is specifically designed to work primarily in the infrared region of the spectrum. Its primary mirror is a golden mirror which reflects 99% of infrared light (as gold is the most efficient reflector of infrared light followed by silver and aluminum). Telescope has specifically designed four scientific instruments installed to capture every trace of light reflected by the mirror. That makes the James Webb space telescope 1000 times more powerful than Hubble.

James Webb is going to be located at the second Lagrange point, which is 1.5 million kilometers from the earth (The distance between earth and moon is only 384,400 km ). So, James Webb has an advantage over Hubble located 570Kms above the earth, hence James Webb will have an unobstructed view of the cosmos.

Then why is 1.5 million km not somewhat close? Well, the answer lies again in the design of the telescope. To collect all the infrared photons reflected by giant honeycomb shape mirror telescope equipment needs to work in -233 C (40K).

To respond to the main question thread, Hubble is able to observe toddler galaxies when the universe is 500-550 million years old. Compared to Hubble JWST, which can observe baby galaxies, which means it can see up to 13 billion years in the past. So, we can’t say that James Webb is a replacement of Hubble, but it is a successor of Hubble. With the help of JWST, we will be able to observe our universe beyond Hubble's deep field. One thing I would like to clear here is JWST cannot see the big bang, but definitely, it can look very near to the big bang may be within 100 million years range.