This is a podcast episode about the James Webb Telescope
The internet recently celebrated images from far-off areas of the universe from the latest eye in the sky - James Webb Space Telescope. JWST isn’t the first time astronomers pointed a space telescope at various heavenly bodies. Years ago, Hubble Space Telescope was launched and brought back the first images of deep space, something that humans have never been able to see before.
But the history of space exploration started many centuries before JWST lifted off from the earth’s surface to bring back the images of the cosmos that broke the internet. From the time human beings started walking on the face of the earth, we have always looked up with wonder at the sky. Heavenly bodies fascinated us in many ways and became an integral part of cultures across the world.
But before we dwell into JWST’s existence and the story behind it, let us rewind some time in the past. Actually, a long time in the past, to the big daddy of all bangs - the Big Bang!
The Big Bang theory describes how the universe expanded from an initial state of high density and temperature. It is the prevailing cosmological model explaining the evolution of the observable universe from the earliest known periods through its subsequent large-scale form. The model offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure.
Big Bang theory is supported by Hubble-Lemarite law which states that further, an object is in the universe, the faster it is moving away from earth. Extrapolating this cosmic expansion backwards in time using the known laws of physics, the theory describes an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning. Detailed measurements of the expansion rate of the universe place the Big Bang singularity at around 13.8 billion years ago, which is thus considered the age of the universe.
After its initial expansion, an event that is by itself often called "the Big Bang", the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms. Giant clouds of these primordial elements—mostly hydrogen, with some helium and lithium—later coalesced through gravity, forming early stars and galaxies, the descendants of which are visible today. Besides these primordial building materials, astronomers observe the gravitational effects of an unknown dark matter surrounding galaxies.
Georges Lemaître first noted in 1927 that an expanding universe could be traced back in time to an originating single point, which he called the "primeval atom". Edwin Hubble confirmed through analysis of galactic redshifts in 1929 that galaxies are indeed drifting apart; this is important observational evidence for an expanding universe.
For several decades, the scientific community was divided between supporters of the Big Bang and the rival steady-state model which both offered explanations for the observed expansion, but the steady-state model stipulated an eternal universe in contrast to the Big Bang's finite age. In 1964, the CMB was discovered, which convinced many cosmologists that the steady-state theory was falsified, since, unlike the steady-state theory, the hot Big Bang predicted uniform background radiation throughout the universe caused by the high temperatures and densities in the distant past.
One of the most important factors supporting the Big Bang Theory is the expansion of the universe. Contrary to popular belief, Big Bang is not an explosion of matter that moves outward to fill the empty space, it is the expansion of the space itself with time, resulting in each point moving away. It is an expansion of space and not an explosion in space.
The need for James Webb came in because it turned out that Hubble wasn’t enough for more deep space investigation. To study about the universe as it existed during its formation, it was essential to be able to see deeper into space.
JWST uses infrared cameras instead of visible light that enables it to look deeper into space. Infrared light travels through the gas clouds and dust in space and enables JWST to see further and detect fainter objects than a regular visible light spectrum camera.
Since James Webb uses infrared cameras, it is important to maintain the temperature of the telescope as low as possible to avoid the images being tainted. For this reason, Webb orbits much further away from earth to avoid contamination of the images being captured. Any amount of heat would result in the contamination of images since anything that emits heat radiates infrared radiation.
As a result of this distance from earth, JWST is not serviceable like the Hubble telescope. Hubble had issues with its mirrors when it was launched and then had to be serviced to add a corrective “lens” to ensure that the images were not blurred.
Also, unlike the Hubble telescope, James Webb couldn’t be assembled in the orbit but had to b launched in one piece which would unwrap itself. This was a complicated process with many points of failure.
JWST is parked in an orbit around a point about a million kilometres from the earth where the effects of the gravitational force of the Sun and Earth act with equal force.
- James Webb was NASA’s second administrator. He lead the Apollo Moon missions
- Projected cost was $1bn which was surpassed in 2007 and crossed $10bn in 2021.
- Launched Dec 25th, 2021
- During its inception and early years, it was called Next Generation Space Telescope (NGST)
- Cold telescope in space is required for capturing the infrared radiations coming from far away objects.
- An expected lifetime of 10 years, but may last more than that
- Since Webb orbits around 1.5 million kilometres from Earth, assembly in space and servicing is impossible
- The primary mirror in Webb is about 6.5 metres in diameter with about 6 times larger area than Hubble
- Mirrors are Beryllium mirrors and are lighter than Hubble’s mirrors although bigger in size
- Five laters of sun shield with vacuum in between acting as insulator
- Located in the second Lagrange point where it is shielded from the Sun and the moon at all the times
- Webb operates at 50K which is 50 degrees above absolute zero (-223 degree C)
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