NASA’s new space telescope may revolutionise the hunt for habitable planets

If all goes to plan, the James Webb Space Telescope — a “transformational” NASA mission designed to observe worlds beyond our solar system — will become the largest and most sensitive telescope ever sent into space when it launches in the early hours of Christmas Day, furthering the hunt for habitable planets that could host alien life.

Scheduled to blast off onboard an Ariane 5 rocket at 12.20pm (UK time), from the European Space Agency’s spaceport in French Guiana, the telescope has been in development for decades at NASA, and costs $10 billion (£7.4 billion). 

Its 6.5-metre primary mirror — or the “eye” through which it will look back in time to observe some of the earliest beginnings of stars, planets, and galaxies — is so large that it has to be folded up to fit inside the rocket for launch. It will unfold during JWST’s month-long journey to a destination almost a million miles from Earth (AKA the second Lagrange point, or L2), where it will orbit the Sun.

However, JWST’s arrival at L2 in working condition isn’t a sure thing. “It’s exciting to think that after so long, we might eventually get this telescope into space. But I’m nervous because we all know that however good the rocket is, there are risks in getting there,” says Prof Martin Barstow, chair of the Space Telescope Institute Council and director of strategic partnerships at Space Park Leicester, speaking to the Guardian. “A whole lot of things have to go perfectly for us to have a working telescope.”

Even if it does avoid the potential risks, scientists will spend a further five months working on the telescope before they begin gathering data in the summer of 2022. Facing away from the Sun, it will then be used to examine alien worlds as they pass in front of other stars in the Milky Way, measuring how infrared light changes when it is filtered through the planet’s atmosphere.

These investigations will help understand how certain planets form and survive under extreme circumstances, and shed light on our own cosmic past. Unless scientists are very lucky, they’re unlikely to spot actual signs of alien life, but they may be able to identify distant worlds that are suitable for habitation.

Speaking to National Geographic earlier this month, Johns Hopkins Applied Physics Laboratory’s Kevin Stevenson (who will observe five planets with the telescope) explained: “Finding life is going to be hard, and I’m not super confident that we will detect biosignatures, but I think we will be able to say something about the atmospheres of these planets around small stars.”

Stevenson also suggests that JWST will help ascertain whether studying the atmospheres of planets as they transit their stars is a useful way to detect signs of life. “We may see that we can’t pull out the signals that we’re looking for,” he adds. “There may be a fundamental limit to what we can learn about potentially habitable planets using the transit technique. And that’s fine, because once we understand that limit, we can move on to other techniques.”

Another large space telescope with the specific purpose of detecting biosignatures on Earth-like alien worlds is already in the works, but won’t launch for decades to come. For now, the James Webb Space Telescope is the best hope scientists have of unravelling the mysteries of distant planets.

“There are thousands of astronomers waiting to use this telescope,” Barstow continues. “It’s important to remember this is a huge endeavour. There will be a lot of people around the world biting their fingernails tomorrow.”

You can watch the launch of the James Webb Space Telescope live on December 25, via the link below.