James Webb Space Telescope

The James Webb Space Telescope (JWST) is one of the most advanced and powerful astronomical observatories ever constructed. Launched on 25 December 2021, it represents an international collaboration primarily between the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and the Canadian Space Agency (CSA). Designed as the scientific successor to the Hubble Space Telescope, JWST aims to explore the universe in the infrared spectrum, offering unprecedented insights into the formation of stars, galaxies, exoplanets, and the early stages of the cosmos.

Background and Development

The conception of the James Webb Space Telescope dates back to the late 1980s and early 1990s when scientists began discussing a successor to Hubble that could see deeper into space and time. Initially called the Next Generation Space Telescope (NGST), it was renamed in 2002 in honour of James E. Webb, NASA’s administrator during the Apollo era, who was instrumental in promoting scientific research within the agency.
The telescope was developed through decades of technological innovation, with contributions from multiple countries and institutions. Its development faced several technical challenges, budget overruns, and launch delays, with costs rising from initial estimates of around $1 billion to nearly $10 billion. Despite these hurdles, JWST became a symbol of modern scientific ambition and international cooperation.

Design and Key Components

The design of JWST incorporates several cutting-edge technologies aimed at capturing faint infrared light from the earliest galaxies. The telescope measures approximately 6.5 metres in diameter, making it about 2.5 times larger than Hubble’s primary mirror.
Key components include:

• Primary Mirror: Composed of 18 hexagonal segments made from beryllium and coated with a thin layer of gold, optimised for reflecting infrared light.
• Sunshield: A five-layered structure roughly the size of a tennis court that protects the instruments from heat and sunlight, keeping them at an operational temperature of around –233°C.
• Scientific Instruments: JWST houses four main instruments — the Near Infrared Camera (NIRCam), the Near Infrared Spectrograph (NIRSpec), the Mid-Infrared Instrument (MIRI), and the Fine Guidance Sensor/Near Infrared Imager and Slitless Spectrograph (FGS/NIRISS). Together, these enable imaging, spectroscopy, and precise target tracking.
• Orbit and Location: JWST orbits the second Lagrange point (L2), approximately 1.5 million kilometres from Earth, where gravitational forces from the Earth and Sun balance, providing a stable environment for long-term observations.

Scientific Objectives

The primary scientific goals of the James Webb Space Telescope are designed to address some of the most profound questions in modern astrophysics:

• Origins of the Universe: By detecting infrared light from distant galaxies, JWST aims to observe the first luminous objects that formed after the Big Bang, roughly 13.5 billion years ago.
• Star and Planet Formation: Infrared capabilities allow JWST to penetrate dense clouds of dust where stars and planetary systems are born.
• Exoplanet Atmospheres: JWST can analyse the chemical composition of exoplanetary atmospheres, searching for molecules such as water vapour, methane, carbon dioxide, and oxygen, which could indicate potential habitability.
• Evolution of Galaxies: By tracing how galaxies change over cosmic time, the telescope contributes to understanding galactic morphology, interactions, and star formation rates.

Engineering Innovations

Several innovations distinguish JWST from its predecessors. Its segmented mirror was designed to fold for launch within the Ariane 5 rocket and then unfold in space—a process involving hundreds of precise movements. The deployment sequence, one of the most complex ever attempted, included the unfolding of the sunshield, mirror alignment, and instrument calibration.