New data from the James Webb Space Telescope is advancing the search for habitable planets – here, NASA scientist Knicole Colon tells Dazed how it works, and how likely we are to meet little green men in our lifetime
It’s easy to get caught up in the stunning images of space that have been beamed back to Earth by the James Webb Space Telescope since it settled into orbit almost a million miles from our home planet earlier this month. Researchers didn’t drop $10 billion on the project just to capture some pretty pictures, though – so what is the JWST actually doing out there?
The answer isn’t so simple, because the truth is that the JWST is doing lots of things. Various experts are given chunks of time to point the telescope at space objects they’re interested in, exploring everything from the origins of the universe, to what happens when galaxies collide. However, a significant portion of this time – around a quarter – is directed at objects on a slightly smaller scale: specifically, exoplanets, or the planets that orbit distant stars. Some of these planets could be habitable; some could even contain traces of alien life.
Late last month we got our most detailed picture of the atmosphere on one of these exoplanets to date, thanks to the JWST, which was trained on a gas giant 700 light-years away, dubbed WASP-39b. By examining the light from a star as WASP-39b passed in front of it, scientists were able to determine the chemicals that make up the planet’s atmosphere.
This is exciting because it demonstrates the JWST’s unprecedented potential for gathering data about the universe, but also because it represents a step forward in the search for life beyond the Solar System. But how is the JWST revolutionising the hunt for habitable worlds and extraterrestrials, and what do we expect to find if the search is successful – are little green men really out there, waiting for us to make contact?
We asked Dr Knicole Colon, who specialises in researching exoplanets at NASA Goddard, to help clear things up.
HOW DO WE DECIDE WHICH DISTANT PLANETS ARE RIPE FOR LIFE?
Onboard the JWST are four different science instruments, Knicole explains. “Think of them like cameras. They collect data that can be transformed into what we call ‘spectra’.” Essentially, this means breaking starlight down into its individual elements and molecules as it passes through an exoplanet’s atmosphere.
“From our point of view, the telescope is looking at a star, the planet passes in front of the star, and then the starlight gets filtered through the planet’s atmosphere. When that happens, we can see what’s filtered out. That is actually what is in the planet’s atmosphere.” Essentially, this allows scientists to see the “chemical fingerprints” of a given planet’s atmosphere. If it contains things like water, carbon dioxide, and methane, that increases the chances of habitability – or that the planet may already host some kind of life.
Sometimes, it’s a case of finding out whether a planet has an atmosphere at all. Many of the exoplanets observed by NASA are small, like Earth, but orbit stars in a very different way. “We take 365 days to orbit the sun, these planets take tens of days to orbit their star,” says Knicole. Activity such as solar flares could have stripped away the atmosphere completely on planets with such a small orbit. “It all ties in... pinpointing these planets and atmospheres, and then moving into the next stage, looking for what we call the building blocks of life.”
WHAT’S SO GOOD ABOUT ABOUT THE JAMES WEBB SPACE TELESCOPE?
Before the James Webb Space Telescope successfully launched earlier this year, the only option for exploring exoplanet atmospheres was the Hubble Space Telescope, which launched into low Earth orbit in 1990. What sets the JWST apart? “It’s a combination of the power of the telescope – because it’s the largest space telescope we’ve ever launched – and [that] it’s optimised to study light that we can’t see: infrared light,” Knicole explains. When looking at starlight that’s filtered out by a planet’s atmosphere, it’s most useful to look at light on the infrared wavelength. “That’s Webb’s wheelhouse,” she adds. “That’s what it was designed for.”
The Hubble Telescope, on the other hand, was only equipped to view ultraviolet, visible, and near-infrared light. That doesn’t mean that Webb’s predecessor didn’t beam back some incredible images, but it does mean that we’re only just beginning to view exoplanet atmospheres in any detail.
WHAT ARE THE CHANCES OF THE JWST DETECTING ALIEN LIFE?
“We’re not taking pictures of little green men yet,” Knicole confirms, to my undisguisable disappointment. For now, it’s more about figuring out which planets could host life, and paving the way for future explorations. Of course, it’s “hard to say” whether JWST will come up with anything concrete in its potential 20-year life cycle.
On a more optimistic note, Knicole thinks that the number of potentially habitable planets is likely to grow with the JWST observations. “I think the number of planets that are the right size and the right temperature is going to continue to increase,” she says. “They still likely won’t be around sun-like stars, but I think Webb will at least be really good at telling us these planets are really viable targets for habitability, and so we should throw everything we’ve got at them.”
“If Webb could last 20 years, by the end we might have a nice little family portrait of these potentially habitable worlds, and molecules we’ve detected. Hopefully it inspires the development of new missions targeted just to study those planets.”
WHY ARE WE SO INTERESTED IN FINDING LIVABLE PLANETS, ANYWAY?
Until we develop the ability to travel through space much, much faster than we can today, many of the exoplanets observed by the JWST are a distant fantasy. Why are we pouring so many resources (and billions of dollars) into exploring them, if we can’t leave our own godforsaken rock to go for an intergalactic holiday, or meet any locals we might discover along the way?
For Knicole, the mission is partly about preparing our future selves. “I don’t know when we’ll have the technology to travel at some reasonable fraction of the speed of light, and try to get to these worlds,” she says. “But if we do all the legwork now, to find as many worlds as we can, then at least we have an inventory. So when we do have the technology to go, we know where we’re going.” Just as the JWST improved on the Hubble, it will also help pinpoint planets worth exploring for future telescopes, meaning that we’ll have an even clearer map by the time we’ve got our hyperdrives up and running.
“A more philosophical answer,” she continues, “is that, even if we can’t find biosignatures in the near future with Webb – and we’ll try our hardest – but we at least haven’t ruled them out. Every little bit helps us understand the age-old question: ‘Are we alone?’”
“Every little bit helps us understand the age-old question: Are we alone?” – Dr Knicole Colon
HOW IS WASP-39b A STEP TOWARD ANSWERING THAT QUESTION?
To untrained eyes, the data on WASP-39b that was shared by NASA last month looks like nothing more than “bumps and wiggles”, but Knicole reassures us that it represents a treasure trove of information. While the planet itself is a “hot Jupiter” – much too hot to sustain life – this information confirms that the JWST is doing its job, and is a reliable tool for future exploration.
“When you are able to take the data from multiple instruments and see the same exact features – we saw water and carbon dioxide, and we saw sulphur dioxide – that is really powerful, essentially, because it shows that what we’re seeing is real. We are seeing real features in this planet’s atmosphere.”
Spotting sulphur dioxide in an exoplanet’s atmosphere for the first time was also important because it’s an example of “photochemistry” – in other words, the chemical is formed through a reaction caused by starlight. “Now we have direct evidence that the molecules produced from these reactions in the atmosphere are definitely there, and that we can detect them with Webb,” Knicole says. “Now we can start to make better predictions of what else we can see with Webb, and whether that could include some kind of biosignature in the future.”
“It’s definitely the first step in a long journey.”