There is a distant world where quartz crystals float above a scorching hot, puffy atmosphere. Vaporized sand grains, not water droplets, form the clouds that fill the sky on 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 one-seventieth of the distance between the Earth and the sun and appears to be covered with a thick dense atmosphere containing large amounts of contains steam.
Or there are the giant, Jupiter-sized planets of the Orion Nebula that have been discovered floating in space, rogue worlds that do not appear to be connected to any parent star – much to the bewilderment of astronomers.
These strange, remote planets could not be more diverse or dramatically different from each other – although they do share one common feature. Their wonders are now revealed by the James Webb Space Telescope (JWST).
Launched on Christmas Day 2021, the $10 billion robotic observatory is currently transforming our knowledge of planets of our galaxy. “It took six months to position the telescope and get its systems functioning properly – meaning 2023 was its first full calendar year of operation,” said astrophysicist Dr Hannah Wakeford, from the University of Bristol. “The results exceeded all our expectations.”
The JWST consists of a 6.5 meter, gold-plated mirror; a sunshade the size of a tennis court; and a variety of complex instruments cooled to temperatures only a few degrees above absolute zero. These features allow the telescope to observe the heavens in infrared radiation, revealing details of the universe just after its Big Bang birth 13.8 billion years ago, and images of stars being born in clouds of dust.
However, the JWST offers science a further gift – because infrared radiation also appears to be ideal for identifying extrasolar planets, or exoplanets, such as worlds that orbit other stars. In doing so, the telescope causes an astronomical upheaval.
For centuries, the only planets known to humans were the few we could see in our solar system. But was the sun’s family typical, scientists wondered? Were planets abundant or rare elsewhere in the galaxy? These questions were crucial because the latter scenario – a cosmic shortage of planets – would mean that extraterrestrial life would also likely be rare.
The problem for astronomers was the simple fact that stars are very bright, but planets are much smaller and much dimmer, and could not be detected next to their brilliant celestial parents. Only at the end of the last century was a new generation of highly sensitive cameras, mounted on telescopes and orbiting observatories, able to detect the slight dimming of exoplanets as they pass in front of stars.
After the first few of these transit observations were made, discoveries began to multiply dramatically. Today, the total number of observed exoplanets stands at 5,566, according to Nasa’s Extrasolar Planet Archive.
Many hundreds are relatively close to Earth and are now ripe for study with the JWST, astronomers say. Wasp-107b and its quartz clouds and the rogue worlds of the Orion Nebula has already been investigated along with a host of other exoplanets.
“Having found all these worlds, we are now in the fortunate position of being able to study them in detail, analyze their atmospheres and even map their features when three decades ago we didn’t know for sure if they even existed at all. not,” said astrophysicist Prof Jayne Birkby of the University of Oxford.
An early target for astronomers using the JWST was Trappist-1, a small, cool star of a type known as a red dwarf. Forty light-years from Earth, it has a family of seven small rocky worlds, three of which lie within a region known as the habitable zone. Here, conditions are neither too hot nor too cold to prevent water from existing as a liquid, a primary requirement for live to thrivesay astrobiologists.
However, analyzes – using the JWST – of two of the star’s inner planets, Trappist-1b and Trappist-1c, have revealed that they either have no atmosphere or only a very thin one. Further JWST studies of the rest of the system are now planned. “Trappist-1’s system still looks promising if you’re looking for a world that could support life,” said astronomer Dr Jo Barstow of the Open University.
Photo: Bill Ingalls/UPI/REX/Shutterstock
However, one special problem affects studies of stars such as Trappist-1. Red dwarfs are spotted. It may not sound like a terminal condition, but it has serious implications, Barstow added. “Our own sun has sunspots associated with intense solar activity, but it has relatively few. In contrast, Trappist-1 has dozens of spots that change all the time, making it very difficult to distinguish between these and features of a planet’s atmosphere. The Trappist-1 system is not going to give up its secrets easily.”
Ultimately, astronomers using the JWST to look for signs of extraterrestrial life look for a set of biological markers known as the Big Four: oxygen, carbon dioxide, water and methane. Their presence in the atmosphere of an exoplanet would be a strong sign that life of some kind exists.
“However, the exact proportions will vary,” Birkby said. “The Earth has an atmosphere that is 21% oxygen, but it would have been very different 2.5 billion years ago when there would have been very little oxygen. The great oxidation event – which occurred when cyanobacteria in the oceans began to produce oxygen through photosynthesis – has not yet begun. However, there was still life on earth at that time.”
What scientists will make of a world whose atmosphere contains all the Big Four remains to be seen. “At present-day Earth-like quantities, 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 exoplanet atmospheres, you’ll still only be making indirect measurements, and saying you’ve definitely found life based on that is hard to justify,” Barstow said.
“Even if you were 99% certain about the claim, there would still be a nagging doubt that what you observed was due to non-biological phenomena.”
The life of the James Webb Space Telescope promises to be an intriguing one – and a long one. The JWST’s flight, on an Ariane 5 rocket, from the European Space Agency’s launch pad in Kourou in French Guiana to its current position in orbit around the sun was nearly flawless. The observatory used very little fuel to maneuver itself to its exact target location – and that means there will be extra to allow the telescope to orient itself for much longer than expected. Space engineers calculated that the JWST’s expected 10-year lifetime could be doubled.
“In many ways this is very good news,” said astronomer Professor Stephen Wilkins, of the University of Sussex. “We will now be able to do much more science with it. However, the telescope will decay as the years pass, as it is hit by meteorites and cosmic rays. This will slowly degrade its performance, so we need to make the most of it while it’s running near optimal conditions.”
Wilkins’ own specialty is the study of galaxies and black holes. “Nonetheless, I think the most exciting science that will be done by the JWST is about exoplanets,” he said. “We’re going to learn so much about the chemistry of their atmosphere and we’re going to find some very strange and bizarre worlds out there. It’s hugely exciting.”
