by There is a distant world where quartz crystals float above a scorching, swollen atmosphere. Vaporized grains of sand, not water droplets, form the clouds that fill the sky of Wasp-107b, a planet 1,300 light years from Earth.
Then there is GJ1214, the sauna planet. With a mass eight times that of the Earth, it orbits its parent star at a distance that is one-seventieth the distance between the Earth and the Sun and appears to be covered by a thick, dense atmosphere containing large amounts of vapor.
Or there are the giant, Jupiter-sized planets of the Orion Nebula that have been discovered floating freely in space, rogue worlds that appear not to be connected to any parent star, much to the bewilderment of astronomers.
These strange and remote planets couldn’t be more diverse or dramatically different from each other, although they share one common characteristic. Its wonders are now being revealed by the James Webb Space Telescope (JWST).
Launched on Christmas Day 2021, the $10 billion robotic observatory is currently transforming our knowledge of the planets in our galaxy. “It took six months to position the telescope and get its systems working properly, meaning 2023 was its first full calendar year of operation,” said astrophysicist Dr Hannah Wakeford of the University of Bristol. “The results have exceeded all our expectations.”
The JWST consists of a 6.5 meter gold-plated mirror; a parasol the size of a tennis court; and a series of complex instruments that are cooled to temperatures just a few degrees above absolute zero. These features allow the telescope to observe the skies in infrared radiation, revealing details of the universe just after its birth in the Big Bang 13.8 billion years ago, and images of stars being born in clouds of dust.
However, JWST offers science an additional gift: infrared radiation is also ideal for studying extrasolar planets or exoplanets, as worlds orbiting other stars are known. With this, the telescope triggers an astronomical revolution.
For centuries, the only planets known to humans were the few we could see in our solar system. But was the sun family typical? scientists wondered. Were planets abundant elsewhere in the galaxy or were they rare? These questions were crucially important because the latter scenario – a cosmic shortage of planets – would mean that extraterrestrial life would likely also be scarce.
The problem for astronomers was the simple fact that the stars are very bright but the planets are much smaller and much dimmer, and cannot be detected next to their bright celestial parents. It was not until the end of the last century that a new generation of highly sensitive cameras, installed on orbiting telescopes and observatories, were able to detect the slight dimming of exoplanets as they passed in front of the stars.
After the first transit observations were made, discoveries began to multiply dramatically. Today, the total number of observed exoplanets amounts to 5,566, according to NASA’s extrasolar planet archive.
According to astronomers, several hundred of them are located relatively close to Earth and are now ready to be studied with the JWST. Wasp-107b and its quartz clouds and the rogue worlds of the Orion Nebula have already been examined along with many other exoplanets.
“Having found all of these worlds, we are now in the fortunate position of being able to study them in detail, analyze their atmospheres and even map their characteristics when, three decades ago, we didn’t know for sure if they existed,” he said. astrophysicist Professor Jayne Birkby of the University of Oxford.
One of the first targets for astronomers using JWST has been Trappist-1, a small, cool star of a type known as a red dwarf. Forty light years from Earth, it is home to a family of seven small rocky worlds, three of them located in a region known as the habitable zone. Conditions here are neither too hot nor too cold to prevent water from existing in liquid form, a primary requirement for life to flourish, astrobiologists say.
However, analyzes (using JWST) of two of the star’s innermost planets, Trappist-1b and Trappist-1c, have revealed that they have no atmosphere or only a very thin one. Further JWST studies of the rest of the system are currently being planned. “The Trappist-1 system still looks promising if we are looking for a world that could support life,” said astronomer Dr Jo Barstow of the Open University.
However, a special problem affects star studios like Trappist-1. Red dwarfs have spots. This may not seem like a terminal illness, but it has serious implications, Barstow added. “Our own sun has sunspots associated with intense solar activity, but it has relatively few. On the contrary, Trappist-1 has dozens of spots that change all the time and that makes it very difficult to differentiate them from the characteristics of a planet’s atmosphere. The Trappist-1 system is not going to reveal its secrets easily.”
Ultimately, astronomers using JWST to search for signs of extraterrestrial life are looking for a set of biological markers known as the Big Four: oxygen, carbon dioxide, water and methane. Its presence in the atmosphere of an exoplanet would be a strong signal that some type of life exists there.
“However, the exact proportions would vary,” Birkby said. “The Earth has an atmosphere that is 21% oxygen, but that would have been very different 2.5 billion years ago, when there would be very little oxygen. The great oxidation event, which occurred when cyanobacteria in the oceans began producing oxygen through photosynthesis, had not yet begun. However, at that time there was still life on Earth.”
It remains to be seen what scientists will do with a world whose atmosphere contains all of the Big Four. “At current Earth-like numbers, it would be hard not to get excited,” Birkby added.
Others, however, sound a note of caution. “Even if you get a perfect profile of gases and water vapor in an exoplanet’s atmosphere, you will only make indirect measurements, and saying that life has definitely been found based on them is difficult to justify,” Barstow said.
“Even if you were 99% sure of the claim, there would still be a lingering doubt that what you were observing was due to non-biological phenomena.”
The life of the James Webb Space Telescope promises to be intriguing and long. The flight of JWST, on an Ariane 5 rocket, from the European Space Agency’s launch pad in Kourou, French Guiana, to its current position in orbit around the sun, was almost perfect. The observatory used very little fuel to maneuver to its exact location, and that means there will be more to allow the telescope to orient itself for much longer than anticipated. Space engineers have estimated that JWST’s expected 10-year lifespan could be doubled.
“In many ways this is very good news,” said astronomer Professor Stephen Wilkins of the University of Sussex. “Now we will be able to do a lot more science with it. However, the telescope will deteriorate over the years as it is impacted by meteorites and cosmic rays. “That will slowly degrade its performance, so we need to make the most of it while running in near-optimal conditions.”
Wilkins’ own specialty is the study of galaxies and black holes. “However, I think the most interesting science that JWST will do concerns exoplanets,” he said. “We are going to learn a lot about the chemistry of their atmospheres and we are going to find very strange and bizarre worlds out there. “It’s tremendously exciting.”
