The James Webb Space Telescope has been launched and promises much

The James Webb Space Telescope (JWST) is going to look at hundreds - possibly thousands - of exoplanets in more detail than we’ve previously been capable of doing. And it’s just been successfully launched - on Christmas Day.

NASA has called it “the premier space science observatory of the next decade”. It’s a massive upgrade from the Hubble Space Telescope. “It’s going to help us unlock some of the mysteries of our universe,” says Greg Robinson, the JWST Program Director at NASA. “I want to say it’s going to rewrite the physics books.”

The James Webb Space Telescope being secured on top of the Ariane 5 rocket, 11th December 2021, before then being encapsulated inside the fairing (Credit: ESA-M.Pedoussaut)

But before any scientific observations can begin, a lot must still go right over the next nail-biting 29 days. Today’s launch - which was undoubtedly a tense time for the 1,200 people across 14 countries who built JWST - was only the beginning. It now needs to travel a million miles into space, making a series of do-or-die manoeuvres that must go exactly as planned. First, the solar array has to unfold to begin supplying electricity for the spacecraft. On its third day, the sunshield needs deploying – five enormous kite-shaped sheets, each the size of a tennis court – which will block the sun’s heat. This is to keep all of JWST’s infra-red instrumentation at low temperatures so they can properly function. No less than 700 components have to function like clockwork.

There’s a multitude of stages for all of JWST’s parts to deploy in exact time-frames. “If the secondary mirror doesn’t deploy successfully, we have no telescope,” Heidi Hammel, Vice President at the Association of Universities for Research in Astronomy, has remarked. On the 7th day, JWST’s 18 gold-plated hexagonal segments - the primary mirror of the telescope - start to unfurl. To successfully reach the correct spot in space, JWST’s thrusters must perform three mid-course corrective burns. So mission success is far from certain. A good launch was just the very beginning.

Artist’s impression of JWST in space (Credit: NASA)

From our point of view, one of JWST’s most exciting missions is to find out whether exoplanets have atmospheres and, if so, what those atmospheres are made of - a crucial step for determining whether they might be habitable. One of the most interesting star systems it will be observing is the TRAPPIST-1 exoplanet system; three of its seven planets are in the habitable zone and one may harbour liquid water.

There’s a slight chance of chemical analysis discovering biosignatures being present on an exoplanet, but observation time for this purpose is limited. Regardless, plans are already underway to design a large space telescope with the specific aim of detecting biosignatures on other Earth-like worlds - although such a successor to JWST won’t launch for decades.

It’s worth noting that in 1989, when the JWST was first proposed, exoplanets hadn’t yet been discovered. So ideas for how to use this telescope have evolved over time.

JWST will use its infra-red capabilities to directly observe a part of space and time never seen before, to learn about how the first stars and galaxies were formed over 13.5 billion years ago.

Although JWST won’t be able to “see” dark matter - which accounts for five times the mass of normal particles in the universe - it will employ gravitational lensing techniques to study the most distant galaxies and look at their rotation, to learn more about how dark matter works.

In our own solar system, JWST will map out the chemical composition of the ice giants, Neptune and Uranus, to see how they differ from the gas giants of Jupiter and Saturn. Some observation time will also be allocated to studying Pluto and the asteroid belts.

Let’s hope that the next 29 days go well, so that JWST can then get to work - and add to our growing knowledge of the universe.

Written by Victoria de las Heras, 25th December 2021