UCL Mathematical & Physical Sciences


Opinion: We have built a time machine and it will launch on Christmas eve

20 December 2021

The James Webb Space Telescope will help us understand how galaxies such as our own Milky Way came into existence, says Dr Aayush Saxena (UCL Physics & Astronomy).

Dr Aayush Saxena (UCL Physics & Astronomy)

The James Webb Space Telescope (JWST), scheduled to launch on Christmas eve, is the flagship observatory jointly developed by Nasa, the European Space Agency (ESA) and the Canadian Space Agency (CSA).

As a successor to the revolutionary Hubble Space Telescope that was launched in 1990, which transformed our understanding of the cosmos, JWST will help astronomers peer further back in time to discover some of the earliest galaxies to have formed in the universe and help us understand how galaxies such as our own Milky Way came into existence.

Operating at infrared wavelengths, the primary mirror of JWST is plated in gold and has a diameter of 6.5 meters, considerably larger than Hubble’s 2.4-metre mirror. A larger collecting area and its infrared observation capabilities make JWST a truly unique telescope, capable of making supremely sensitive observations of stars in distant galaxies as well as the atmospheres of potentially habitable planets orbiting other stars within our galaxy.

JWST’s journey from concept to launch readiness, however, has been riddled with delays and budget overruns. The telescope was initially planned to launch in 2007 with a budget of $500 million. The current launch date of December 2021 translates to over a decade of delays, with its current estimated cost being roughly touching $10 billion.

Several technical challenges had to be overcome throughout the designing and implementation of JWST, including a major redesign in 2005. As things stand, JWST is on schedule to be launched aboard an Ariane 5 rocket supplied by ESA from Kourou in French Guiana, an event for which astronomers, as well as science enthusiasts around the world, will be crossing their fingers and holding their breaths.

A successful launch is only the first step in a series of extremely complicated manoeuvres that must be executed to perfection in order to place the James Webb Telescope in position. Unlike Hubble, which orbits the Earth, JWST will be located near the second Lagrange point (L2), orbiting the sun roughly 15,00,000 km away from Earth. JWST’s carefully chosen location ensures that the telescope can always face away from the sun, which is necessary to carry out ultra-sensitive observations of the cosmos. However, this also means, unlike Hubble, JWST cannot be serviced by astronauts, making the launch and deployment of JWST one of the most challenging space missions with absolutely no margin for error.

Just over 30 minutes after launch, JWST will separate from the Ariane rocket and deploy its solar arrays, which will supply it with the power it needs to continue along its journey towards L2. As JWST cruises along its path, the massive sun shields required to keep the telescope cool begin deployment, not opening fully just yet. A week after launch, the sun shields will begin unfolding completely to a size nearly as large as a tennis court. Nearly two weeks after launch, the 6.5-meter diameter primary mirror, which was initially folded away to fit inside the Ariane launch vehicle, begins to unfold.

Finally, nearly 30 days after launch, an almost fully deployed JWST will reach L2, and final orbital corrections and placements can now commence. Once in position, the complex task of switching on the science instruments, testing and calibration can begin, which can take up to six months before any scientific observations are taken.

Once fully operational, JWST will begin to survey the cosmos in a bid to answer some of the most fundamental questions surrounding the origin of stars and black holes in galaxies as well as life on planets. Some of the key science goals that will be achieved thanks to JWST include studying the formation of galactic structure nearly 13.5 billion light-years away, at a time when the Universe was in its infancy and the first stars were only just emerging out of the darkness and bathing the Universe in light.

JWST will also perform a census of the faintest galaxies across time, helping astronomers understand how galaxies have assembled over billions of years. On slightly smaller scales, thanks to its infrared capabilities, JWST will be able to see through clouds of thick cosmic dust that obscures our vision at optical wavelengths, into regions where new stars and planetary systems are born.

The telescope will also help study the atmospheres of potentially habitable exoplanets orbiting other suns, in addition to giving a detailed view of objects within our own solar system.

A team of astronomers that I am leading has been awarded observing time on the James Webb Telescope, through a highly competitive call for proposals, to observe some of the most distant galaxies hosting supermassive black holes that are actively accreting material from their surroundings. These observations will help shed light on the complex interactions between supermassive black holes, that are postulated to exist in the centre of almost every massive galaxy, including our Milky Way, and the distribution of stars and gas within galaxies that host them.

The James Webb Space Telescope represents a giant leap forward, not only scientifically but also technologically, to gain a better understanding of the origin of the vast cosmos that we are a part of. The effort of thousands of engineers and scientists worldwide that have led to the realisation of a machine as powerful and revolutionary as JWST is a testament to what can be achieved when humanity sets aside its differences and collectively pushes towards a common goal.

JWST will truly traverse previously uncharted cosmic territory, transforming our understanding of where we came from and inspiring a new generation of scientists and astronomers in the process.

This article first appeared in India Today on 20th December 2021.