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James Webb Space Telescope

Last updated date: 09th Apr 2024
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What is the James Webb Telescope?

The James Webb Space Telescope (JWST) is a space telescope primarily designed for infrared astronomy. As the largest optical telescope in space, its high infrared resolution and sensitivity allow it to see objects that the Hubble Space Telescope cannot see because they are too early, distant, or faint. This is expected to enable a wide range of astronomical and cosmological investigations, such as the observation of the first stars and the formation of the first galaxies, as well as detailed atmospheric characterization of potentially habitable exoplanets.

James Webb Telescope Power

Astronomers at NASA, the European Space Agency, and the Canadian Space Agency recently released an unprecedented view of the Tarantula Nebula, a massive region of swirling gas and dust. This nebula, which is 161,000 light-years away (relatively close in cosmic terms), is also "home to the hottest, most massive stars known." The James Webb Space Telescope, which captures unprecedented amounts of light from deep space and views wavelengths that our eyes cannot see (infrared light), revealed thousands of massive, previously unseen stars in that central cluster.

James Webb Telescope Mission

The James Webb Space Telescope has four primary objectives:

  • To look for light from the universe's first stars and galaxies after the Big Bang

  • To investigate the formation and evolution of galaxies

  • To comprehend the formation of stars and planets

  • To investigate the origins of life and planetary systems

These objectives can be accomplished more effectively by observing in near-infrared light rather than visible light. As a result, unlike the Hubble Telescope, the JWST's instruments will not measure visible or ultraviolet light, but will have a much greater capacity for infrared astronomy. JWST will be sensitive to wavelengths ranging from 0.6 to 28 m (corresponding to orange light and deep infrared radiation at around 100 K or 173 °C).

JWST could be used to gather data on the dimming light of KIC 8462852, a star discovered in 2015 with some unusual light-curve properties. It will also be able to detect methane in an exoplanet's atmosphere, allowing astronomers to determine whether or not the methane is a biosignature.

Telescope Structure

The James Webb Space Telescope is the biggest space telescope ever constructed. It is nearly double the size of the Hubble Telescope (13m long) and roughly half the Hubble’s weight (6,500kg). Its humongous sun shield stand measures 22m by 12m, almost the same dimension as a tennis court.

James Telescope’s gold-coated mirrors have a cumulative diametre of 605cm, more than twice the diameter of Hubble (240cm). In short, JWST will roughly have a fifteen times broader view than the Hubble Space Telescope.

The optical telescope components of the primary mirror have eighteen six-sided mirror segments, which are made of gold-coated beryllium. This grants the JWST a light-gathering area about 5.5 times as big as Hubble’s area.

Hubble captures images from the range of visible, ultraviolet and near-infrared spectra. On the other hand, the James Webb Space Telescope will detect objects in the range of long-wavelength normal red light and mid-infrared spectrum. This will allow the detection of high-redshift celestial bodies that are too faint, distant, and old.

The ideal working temperature of the Webb telescope is below -223 °C. By maintaining such a low temperature, it will be able to detect faint signals in the infrared spectrum without the intrusion of warmer signals of objects.

It is orbiting near the Sun-Earth L2 Lagrange area, around 1.5 million kilometres away from the Earth. A five-layered windshield guards it against the Sun’s direct heat waves.

James Webb Space Telescope

James Webb Space Telescope

Important Questions

1. How does the James Webb Space Telescope expand our understanding of galaxies?

Ans: Galaxies show us how matter is organised on a large scale in the universe. Understanding galaxies is critical if we are to comprehend the origins of the universe and its evolution over time. By analysing some of the earliest galaxies and comparing them to modern galaxies, we may be able to understand the development and evolution of galaxies. Observations from events that occurred during the universe's formation will allow scientists to solve unsolved mysteries.

2. Briefly describe the technology used in JWST.

Ans: The JWST is envisioned as an integrated telescope that incorporates features from predecessors, such as the Hubble and Spitzer telescopes. JWST's major technological innovations include:

  • Cryogenic mirrors that are lightweight

  • The process of aligning the JWST mirror segments is known as wavefront sensing and control.

  • Infrared detectors that are extremely sensitive.

  • Integrated Circuit for Cryogenic Data Acquisition.

  • To see faint infrared emissions from astronomical objects, the JWST telescope and instruments must be cooled below 50 degrees Celsius. This is done by the sunshield.

  • Microshutters

Solved Examples

1. In an astronomical telescope, the focal length of the objective lens is 100cm and the focal length of the eyepiece lens is 8cm. What is the magnifying power of the telescope?


The magnifying power of the telescope is given by:

M= -focal length of the objective lens/focal length of eyepiece lens

M= -100cm/8cm

M= -12.5

Here, the minus sign indicates that the image is inverted.

2. A simple telescope consists of two convex lenses, the objective and the eyepiece, which have a common focal point P, as shown in the figure above. If the focal length of the objective is 1.0 metre and the angular magnification of the telescope is 10, what is the optical path length between objective and eyepiece?


Magnification(M)= focal length of the objective/focal length of the eyepiece

Since M=10, focal length of the objective= 1

Focal length of eyepiece= focal length of objective/Magnification= 1/10 = 0.1

d= focal length of objective+focal length of eyepiece = 1+0.1 = 1.1 m


The JWST is the most advanced telescope in existence. It will use cutting-edge technology to offer profound insights into a vast, undiscovered universe. The observations by this telescope are likely to expand our understanding of galaxies and the formation of planets including earth. The James Webb Space Telescope (JWST) is a space telescope designed primarily to conduct infrared astronomy. As the largest optical telescope in space, its high infrared resolution and sensitivity allow it to view objects too early, distant, or faint for the Hubble Space Telescope.

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FAQs on James Webb Space Telescope

1. How is the James Webb Space Telescope different from the Hubble Telescope?

The JWST is distinct from the Hubble Telescope in several ways:

  • Wavelength: Hubble's primary capabilities are in the ultraviolet and visible ranges, whereas the James Webb telescope will primarily observe in the infrared.

  • Dimensions: The mirror area of the Webb telescope is larger than that of its predecessors. The sunshield on Webb's telescope is the size of a tennis court.

  • Orbit: The Hubble Space Telescope orbits the Earth at a height of 570 kilometres, while the JWST will remain in Earth-Sun orbit at the L2 point. 

  • Observation: The James Webb telescope would be able to see 'baby galaxies,' whereas Hubble could only see 'toddler galaxies.'

2. Why is infrared light important for astronomical observations?

Infrared light is a type of electromagnetic radiation with a wavelength longer than visible light. It is used in remote controls, burglar alarms, photography, and thermal scanning. It is more important in astronomy for the following reasons:

  • Infrared radiations can penetrate dust particles, allowing for clear observations.

  • Infrared wavelengths are simply superior for observing certain objects. Some chilly, low-energy matter bodies, such as people or young planets, emit infrared radiation but produce little visible light.

  • The redshift phenomenon is caused by Einstein's theory of general relativity, which states that the universe is expanding. As the universe is expanding, light from stars that emit shorter ultraviolet and visible wavelengths is stretched to longer wavelengths of infrared light. Thus, studying infrared radiation will help us understand the origin and evolution of the universe.

3. What are black holes? Is JWST going to study black holes?

Albert Einstein predicted black holes as part of his general theory of relativity. These are massive structures with a strong gravitational pull. They attract everything that passes through their gravitational field, including light. They are called black holes for these reasons. The study of black holes necessitates an examination of the entire electromagnetic spectrum. The JWST is a powerful telescope, but it cannot detect black holes on its own. Its data can be combined with that of other telescopes, such as the Event Horizon Telescope, the Square Kilometre Array, and other NASA missions.