THE SEARCH FOR LIFE
ANOTHER EARTH
A LITTLE UNDER TWO YEARS AGO, THE JAMES WEBB SPACE TELESCOPE CHANGED OUR HORIZONS, ENABLING US TO SEE MORE THAN EVER. BUT EVEN BEFORE WEBB LAUNCHED, ITS SUCCESSORS WERE BEING DEVELOPED AND THIS NEXT GENERATION OF SPACE OBSERVATORIES WILL HAVE LIFE ON OTHER PLANETS FIRMLY IN THEIR SIGHTS
by DR STUART CLARK
Webb may have detected traces of water in the gas giant WASP-18b’s atmosphere
ILLUSTRATION: MAGIC TORCH
BBC TWO
Watch Prof Brian Cox’s new series The Planets, coming soon to BBC Two. Check Radio Times for details.
It has been just 18 months since an Ariane 5 rocket launched the James Webb Space Telescope into space. A collaboration between NASA, the European Space Agency (ESA) and the Canadian Space Agency, Webb has been widely touted as the successor to the Hubble Space Telescope. Indeed, it possesses observational capabilities that the astronomers who launched Hubble back in 1990 could only dream of.
Yet even as Webb shot into space on 25 December 2021, the astronomers watching it were already dreaming of the telescope that might succeed it. This was because they already knew the extent of Webb’s potential: the size of its mirror, the wavelengths it could observe and the capabilities of its instruments.
“Even before it was launched, we were like, ‘we need this other telescope that’s going to be bigger,” says Sarah Rugheimer, professor of astrophysics at York University, Toronto, Canada.
Big telescopes take a long time to develop – decades in most cases – and so planning starts early. “You don’t just wait to see what happens with a telescope like Webb because you already know, theoretically, what some of its limitations will be,” says Rugheimer.
In her field of astrobiology, Rugheimer is interested in looking for signs of life on planets orbiting stars other than our own. The best way to do this is to isolate the light from these exoplanets and analyse it for gases that may betray extraterrestrial metabolisms at work. Webb is able to do this for larger, gaseous planets, but those aren’t the ones where we expect life to exist. Astronomers believe that rocky Earth-sized planets are much better targets. But as powerful as Webb is, it doesn’t have the light-gathering ability to do this type of analysis for more than about five of these kinds of planets.
“When you’re thinking about finding life in the Universe and you ask someone, ‘Well, how many planets would you look at?’ They’re not gonna say five. They’re gonna say hundreds or more,” says Rugheimer.
Exoplanet GJ 486 b (illustrated here), may have an atmosphere that contains water vapour
NASA/ESO, SHUTTERSTOCK, BRET HARTMAN
So, when it comes to searching for life on exoplanets, Webb is a testing ground for a successor telescope that will be bigger and better.