Launched on Christmas Day 2021, the James Webb Space Telescope (JWST) is already changing our understanding of planets in our solar system and far beyond. As a versatile satellite observatory, JWST has a clear view from its orbital position a million miles from Earth in space. This gives it a major advantage over ground-based telescopes, which have to look out into space through Earth’s hazy atmosphere.
JWST collects five times as much light as the Hubble Space Telescope (HST), allowing its spectroscopic capabilities to detect faint signals from distant worlds.
“Only a very small number of molecules, such as water, carbon monoxide and sodium, could be observed in front of the James Webb Space Telescope,” said Jérémy Leconte, an astrophysicist at the University of Bordeaux in France.
Previous missions and observations from Earth have discovered thousands of exoplanets (those outside our solar system), and astronomers are already using the JWST’s unique capabilities to study the building blocks of life in the universe.
Earlier this year, the James Webb Telescope allowed astrophysicists to observe an exoplanet orbiting a Sun-like star 700 light-years away. Starlight penetrating the atmosphere of hot Jupiter-like planet WASP-39b is giving astronomers a glimpse into the chemistry of alien skies.
From Earth, telescopes struggle to see carbon dioxide on exoplanets because they have to see through the CO2 in the planets’ atmospheres. The JWST observatory enables detection of a wider range of molecules, including carbon dioxide, in the WASP-39b sky. The presence of carbon dioxide in the atmosphere may indicate that organic life exists on the planet.
“This is really a turning point,” said Leconte. “We really need to look at planets around us near stars. This is our best chance to characterize their atmosphere.”
He is particularly interested in seven rocky planets orbiting the dwarf star TRAPPIST-1, which is 40 light-years away, and especially in their atmospheres. The planets exist in the habitable zone, which means it has the right temperatures for water to stay liquid.
When scientists make predictions about an exoplanet’s atmosphere, they usually assume that it is homogeneous—the same conditions prevail everywhere. This is probably not true.
Leconte (as part of the Horizon-funded WHIPLASH project) has developed a 3D simulator to conduct tests on simulated planets with known properties such as the presence of liquid water. Using simulated planets for these tests is like the answers at the end of a math book: tests can be run and the models’ answers compared to known properties.
Many thousands more exoplanets are likely to be discovered in the coming years – including those found with the new space telescope. Scientists want to know if their models can provide accurate insights. Some of the answers to questions about distant exoplanets may lie near our solar system, on the four largest planets – Jupiter, Saturn, Uranus and Neptune.
The Juno orbiter mission has provided spectacular views of Jupiter, while the Cassini spacecraft has revealed details about the planet Saturn. Earlier, the Voyager 2 spacecraft, which flew past Neptune and Uranus, captured images of their atmosphere.
“We captured gorgeous images of these planets, with all these swirling storm systems and candy-colored streaks depicting large-scale weather circulation patterns,” said Leigh Fletcher, a planetary scientist at the University of Leicester. “But it’s just a snapshot of their atmosphere and climate at any given point in time.”
To understand climate and weather patterns, Fletcher leads a project called GIANTCLIMES, which is piecing together scattered pieces of the puzzle of their ever-changing atmospheres. They used previous observations from telescopes on Earth to understand the natural cycles on the four giant planets over many decades. This work has prepared the ground for the highly anticipated new maps of these worlds from JWST.
Uranus and Neptune are the most distant planets in the solar system, and these so-called “ice giants” still carry an air of mystery. They consist mainly of hydrogen, helium and other gases such as methane.
“There is so much potential for brand new discoveries [with these two planets]’ Fletcher said. “Compared to the better-studied gas giants, we don’t have a good grasp of how the atmospheres of these ice giants work [Jupiter and Saturn].”
Saturn is now known to have massive storm systems, and Neptune can have methane blizzards. The key variable in weather patterns is always temperature, with freezing cold temperatures on distant Neptune and Uranus.
Progress has already been made with the publication of the first-ever maps of atmospheric temperatures high in the stratosphere of Uranus. This revealed surprising seasonal circulation systems and bright spots over the poles.
It also predicts that giant planets, often titled on their axis, will have extremely long seasons. “We see seasons that modulate atmospheric temperatures, clouds, and precipitation as we do on planet Earth,” Fletcher said, “but we also see regular natural cycles in the atmosphere that aren’t seasonal. We are just beginning to understand the weather on giant planets.”
Neptune’s atmosphere also showed significant storm and weather activity, but the team was surprised to find that the planet appears to have cooled rather than warmed over the summer.
GIANTCLIMES is a support act for the arrival of JWST. The new telescope has already observed Jupiter and will turn to Uranus and Saturn in the near future, and then Neptune in early 2023, to allow comparisons between planets.
“How the climate works on the four worlds is really at the core of what we’re trying to understand,” Fletcher said. It is expected to provide more insight into the natural cycles of climate variability as evidenced on Jupiter, Saturn, Uranus and Neptune. Their extremes may even tell us more about Earth’s own climate and weather patterns.
Studies on the four giants are also relevant to exoplanet research. “We have a collection of different planetary atmospheres in our solar system that provide a template for what we might expect around other stars,” enthused Fletcher.
“Perhaps these exoplanetary targets also exhibit similar natural cycles, and the end goal is to try to have weather forecasts or climate predictions for all planets, not just those in our solar system,” Fletcher concluded.
JWST will give scientists better insights into the skies of planets in the most remote reaches of the Solar System, but also worlds light-years away, some of which may be surrounded by protective atmospheres and terrestrial conditions conducive to extraterrestrial life.
“Two fields in astrophysics are moving fast. They’re exoplanets and cosmology, which really boils down to the question of God and life, so where does the universe come from and where do we come from,” Leconte said.
The research in this article was funded by the European Research Council (ERC) of the EU. The article originally appeared in horizonthe EU magazine for research and innovation.
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