Why Infrared Detectors Are Used In Webb Telescope?

The James Webb Space Telescope, the most powerful telescope ever made, was launched on December 25, 2021. It was deployed in a solar orbit near the Sun–Earth L2 Lagrange point, about 1.5 million kilometres (930,000 mi) from the Earth.

Scientists are confident that this telescope is replacing the iconic Hubble Telescope which has been taking amazing pictures for nearly 30 years.

Objective Of James Webb Telescope.

The JWST is tasked with investigating some of the most distant and difficult-to-see portions of the sky using its infrared sensors, assisting in the search for exoplanets and exploring the universe’s early days. 

Webb’s NIRCam Instrument

Webb’s primary imager will cover the infrared wavelength range of 0.6 to 5 microns and is known as the near-infrared camera (NIRCam).

The light from the earliest stars and galaxies in the process of formation, the population of stars in adjacent galaxies, as well as young stars in the Milky Way and Kuiper Belt objects, will be detected by NIRCam.

NIRCam has coronagraphs, which are instruments that allow astronomers to photograph very faint objects surrounding a bright core source, such as star systems.

The coronagraphs on NIRCam function by blocking the light from a brighter object, allowing you to focus on the view in front of you – just like covering your eyes from the sun with an upraised hand allows you to focus on the vision in front of you.

Astronomers intend to use the coronagraphs to detect the features of planets orbiting neighboring stars.

What Is Infrared?

Infrared is often known as infrared light, is a type of electromagnetic radiation (EMR) having wavelengths that are longer than visible light.

As a result, it is not apparent to the naked eye. IR wavelengths are commonly thought to range from roughly 1 millimeter (300 GHz) to the visible spectrum’s nominal red edge, around 700 nanometers (430 THz).

Longer infrared wavelengths (30m-100m) are occasionally included in the terahertz spectrum. Infrared wavelengths account for nearly all black-body radiation from objects near room temperature.

Infrared is a type of electromagnetic radiation that transmits energy and momentum and has qualities that are similar to both a wave and a particle, the photon.

Why Does The James Webb Telescope Use Infrared?

The JWST examines infrared light in two wavelength ranges:

1.) Near infrared light- Near-infrared spectroscopy (NIRS) is a spectroscopic technique that utilises the electromagnetic spectrum’s near-infrared region (from 780 nm to 2500 nm). It has wavelengths that are extremely similar to visible red light.

2.) Mid Range infrared light- The mid-infrared, or middle band, has a wavelength range of around 1,300 nm to 3,000 nm, or 1.3 to 3 microns, and a frequency range of 20 THz to 215 THz.

In comparison to the near- and far-infrared regions, this form of infrared emits modest heat and is found between the red end of the visible light spectrum and microwaves.

How Does Infrared Help?

Since heat is associated with mid-range infrared. Almost everything produces light, even humans produce light. The temperature of an object influences the wavelength of light it emits.

The shorter the wavelength of light, the hotter it gets. While light emitted in the mid-infrared spectrum cannot be seen, it can occasionally be felt. This can easily be seen by the infrared cameras.

What Is the Doppler Effect?

The Doppler effect, also known as Doppler shift, is a phenomenon that occurs when the source of waves moves in relation to an observer.

When a car passes you at a high speed, you can hear it: the sound changes frequency as the source moves toward you and then away from you.

When the vehicle is approaching you, the sound has a shorter wavelength and so a higher pitch, and when it is traveling away, the sound has a longer wavelength and hence a lower pitch.

How Can Doppler Effect Help Our Webb Telescope?

Light can also produce a Doppler effect, however, because light travels at such a fast speed (3 x 10⁸ m/s), the effect isn’t evident in many cases.

However, because the universe is expanding, nearly all of the galaxies visible from Earth are moving away from us. As a result, we perceive their light to have a longer wavelength.

We call this a redshift because the wavelengths are longer and therefore more red. The red shift is so great for really far away objects that the important material is in the infrared spectrum.

Since the JWST observes infrared light, scientists will require as much darkness as possible around the telescope. That means the telescope must be exceedingly cold to avoid releasing infrared radiation of its own.

It has a sunshield for this reason. It will keep the major instruments cool by blocking sunlight from reaching them. It will also help to remove surplus light so that the webb can pick up the exoplanets’ comparatively faint light as they orbit their much brighter host stars.

Let’s See Some Other Reasons Why JWST Is Using Infrared

One reason is that the ultraviolet and visible light released by the universe’s first luminous objects when it was young has been stretched by the expansion of the cosmos and now reaches us as infrared light, nearly 13 billion years later. Webb will be on the lookout for the first light.

Another explanation is that stars and planets are formed in gas and dust clouds, which obscure our perspective. We can see inside these clouds because infrared light penetrates them.

What Are The Advantages Of Using Infrared?

  • Observing Star Formations. Since stars and planetary systems emerge from the dusty leftovers of past generations of stars, the infrared section of the spectrum is a great ‘window’ into processes like star and planet formation. We can really see through dusty nurseries and observe new stars and their nascent planetary systems in formation because infrared light is scatter less by dust than shorter wavelengths of visible light.
  • Observing Light Wavelengths. Infrared is also the optimum light for viewing some objects. Light wavelength and temperature are inseparably linked. The shorter the wavelength of light that something emits, the hotter it is, and the longer the wavelength of light that it emits, the colder it is. Infrared light also allows us to glimpse galaxies as they were in the distant past, as previously explained.

How Will Webb Observe Exoplanets?

Planets are cooler than stars and do not emit visible light. They partially reflect visible light from their parent stars but do not emit any visible light of their own.

The planet absorbs some of the light from the parent star and re-emits it at infrared wavelengths back into space. They are brightest and “glow” in infrared wavelengths, which is interesting.

Furthermore, many compounds radiate at a variety of infrared wavelengths and absorb light at the same wavelengths.

Infrared viewing is therefore ideal for researching planets and their chemistry, not just those in our own solar system but also those orbiting nearby stars.


The Webb telescope, which is the successor to NASA’s Hubble Space Telescope, is the world’s most advanced space observatory.

The Webb telescope is planned to study unknown planets around distant stars, see the most distant objects in the universe, and offer photographs of the earliest galaxies when they were forming.

Since it is unclear how the cosmos evolved from a simpler state of hydrogen and helium to the universe we see today, the Webb telescope will glimpse distant realms of space and a period of time never seen before, assisting us in answering these crucial issues. Infrared help a lot in finding distant objects like exoplanets,stars, and even galaxies.

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