Relevance: GS-3: Awareness in the fields of Space

Key Phrases: James Webb telescope, Infrared astronomy, NASA, European Space Agency (ESA) and the Canadian Space Agency (CSA), Origins of Life, Planetary Systems, Optical telescope, Hubble Space Telescope.

Why in News?

• NASA's latest deep-space telescope continues to shock astronomers and amateurs with jaw-dropping new images captured from the outer reaches of the cosmos.

What is James Webb Space Telescope?

• The James Webb Space Telescope (JWST) is a space telescope designed primarily to conduct infrared astronomy.
• As the largest optical telescope in space, its greatly improved infrared resolution and sensitivity allow it to view objects too early, distant, or faint for the Hubble Space Telescope.
• This is expected to enable a broad range of investigations across the fields of astronomy and cosmology, such as observation of the first stars and the formation of the first galaxies, and detailed atmospheric characterization of potentially habitable exoplanets.
• It is a joint venture between the US (Nasa), European Space Agency (ESA) and the Canadian Space Agency (CSA).

Location and orbit:

• JWST operates in a halo orbit, circling around a point in space known as the Sun-Earth L2 Lagrange point, approximately 1,500,000 km (930,000 mi) beyond Earth's orbit around the Sun.

The science goals for the Webb can be grouped into four themes:

• The End of the Dark Ages: First Light and Reionization:
  • JWST will be a powerful time machine with infrared vision that will peer back over 13.5 billion years to see the first stars and galaxies forming out of the darkness of the early universe.
• Assembly of Galaxies:
  • JWST's unprecedented infrared sensitivity will help astronomers to compare the faintest, earliest galaxies to today's grand spirals and ellipticals, helping us to understand how galaxies assemble over billions of years.
• The Birth of Stars and Protoplanetary Systems:
  • JWST will be able to see right through and into massive clouds of dust that are opaque to visible-light observatories like Hubble, where stars and planetary systems are being born.
• Planetary Systems and the Origins of Life:
  • JWST will tell us more about the atmospheres of extrasolar planets, and perhaps even find the building blocks of life elsewhere in the universe. In addition to other planetary systems, JWST will also study objects within our own Solar System.

Terminologies associated with working of JWST:

• Waves and wavelength
  • Some waves need a medium to travel — sea waves need water; sound waves need air and other waves don’t need any medium to propagate.
  • Electromagnetic waves, which are waves of energy, are like that — they originate somewhere, and keep radiating through space unless halted by an object, like earth. Higher the energy, the shorter the wavelength.
  • Wavelength is the distance between two successive crests of a wave; the number of peaks per second is called ‘frequency’.
  • So, wavelength and frequency are related — the higher the wavelength, the smaller the frequency. Waves are classified according to their wavelength.
• Electromagnetic spectrum
  • Electromagnetic waves come in a variety of wavelengths, depending upon their source.
  • In the descending order of wavelengths (ascending order of frequencies), they are: radio waves, microwaves, infra-red, or IR, (further classified as far, middle and near), visible light (red, orange, yellow, blue, violet), ultra-violet, X-rays and gamma rays.
  • Visible light is a mixture of the colours mentioned; One can split a light ray through a prism, and can get a spectrum of these colours.
  • Radio waves bring music to our pocket radios; microwaves are what people use to talk to each other on the phone;
  • IR, because they come from heat, helps detect if anyone has a fever, see people in the dark, and is also used by the Webb telescope to ‘see’;
  • Visible light, ultra-violet, and X-rays; gamma rays, the shortest wavelength and the highest energy, are produced when stars explode.
• Doppler Effect and redshift
  • If the star is moving away, then, due to the Doppler Effect, the wave of the light will get elongated and the wavelength will increase. The wavelength will ‘shift’ towards the red colour, which is the longest wavelength of visible light.
  • The farther the emitting object, the more ‘red’ the spectrum will have. This is called the ‘red shift’. The extent of redshift reveals how far the emitter is.
  • If the object pulls away further, it will become invisible — it will move from optical to near IR, and further to middle and far IR.
  • Similarly, if an object is coming towards the telescope, there will have a ‘blue shift’.

How does the Webb telescope work?

• Optical telescopes, like the Hubble, pick up light from distant galaxies; Webb is designed to sense IR, which means it can receive radiation from galaxies that have moved very far.
• For example, it has taken IR radiation from galaxies that are 13.1 billion light years away - it has taken the light (now infra-red) 13.1 billion years to reach the Webb, meaning the Webb is looking at something as it was 13.1 billion years ago.
• Till now it has taken IR of 5 microns in wavelength; it can go deeper to 28 microns.
• The universe is believed to have formed 13.8 billion light years ago; Webb can see the universe as if it was just a few hundred million years old.
• While the red-shift reveals how far the source is, analysis of the spectrum can tell what the radiation has passed through because each element has its unique ‘spectral fingerprint’.
• Scientists can tell whether the source has hydrogen or sulphur or whatever. That’s how they know that an exoplanet that Webb caught has water vapour in its atmosphere.

Source: The Hindu BL

Mains Question:

Q. What is James Webb Space Telescope? Enumerate its objectives and also explain its working?