The mighty Webb telescope doesn’t need to take great pictures to revolutionize our understanding of the cosmos.
Astronomers focused the space observatory — which this year successfully reached its outpost a million miles from Earth — on the Saturn-like exoplanet (meaning planet beyond our solar system) WASP-39 b. It is a hot gas giant that orbits a star 700 light-years away. Previously, scientists used specialized instruments aboard Webb to detect gaseous carbon dioxide in this extreme world.
Now, for the first time, they’ve discovered “a full menu” of atoms and molecules in an exoplanet’s clouds, and some are interacting. This latest discovery demonstrates that astronomers can peer into the atmospheres of strange exoplanets and decipher what is happening or being chemically produced — and whether these worlds could then contain conditions that could potentially harbor life. (On our planet, atmospheric chemistry, which is responsible for creating an insulating atmosphere and protective ozone layer, is vital for life.)
Light from a star can often fuel chemical reactions on a planet, a process called “photochemistry.” This is what is happening on WASP-39 b.
“Planets are sculpted and transformed by orbiting within the radiation bath of the host star,” Natalie Batalha, an astronomer at the University of California, Santa Cruz, who contributed to the new research, said in a statement. “On Earth, these transformations allow life to thrive.” (The five research papers showing the discovery are listed in this UC Santa Cruz news release.)
What the giant James Webb telescope will see that Hubble can’t see
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In particular, the Webb telescope has detected the presence of water vapor, sulfur dioxide, carbon monoxide, sodium and potassium, among other elements. To detect such molecules on distant planets, astronomers aim the observatory at known exoplanets in our galaxy, the Milky Way. Then, as Mashable explained earlier, they do something very profoundly clever:
They will wait for the planets to travel in front of their bright stars. This starlight passes through the exoplanet’s atmosphere, then through space, and finally into instruments called Webb’s onboard spectrographs (a strategy called “transit spectroscopy”). They are essentially hi-tech prisms, separating light into a rainbow of colours. Here’s the big trick: Some molecules, like water, in the atmosphere absorb specific types, or colors, of light. “Each molecule has a specific diet,” explained Néstor Espinoza, an exoplanet researcher at the Space Telescope Science Institute, which manages the James Webb Space Telescope.
So if that color doesn’t appear in the color spectrum observed by a Webb spectrograph, it means it has been absorbed (or “consumed”) by the exoplanet’s atmosphere. In other words, that element is present in the skies of that planet. The spectrograph produces lines (designating different types of light), not pretty pictures; but it is a wealth of invaluable information.
The particularly tantalizing detection on WASP-39b is sulfur dioxide, which is produced when light from a star hits a planet’s atmosphere. Using computers, the researchers simulated conditions in this distant atmosphere and determined that photochemistry formed this molecule in WASP-39 b’s thick, fluffy clouds.
A graph showing the chemical reactions in WASP-39’s atmosphere b.
Credit: NASA/JPL-Caltech/Robert Hurt; Center for Astrophysics-Harvard & Smithsonian / Melissa Weiss
“On Earth, these transformations allow life to thrive.”
Now, astronomers know they can use Webb to search for dynamic atmospheres on other worlds far out in space.
“We will be able to see the big picture of exoplanet atmospheres,” Laura Flagg, an exoplanet researcher at Cornell University who worked on this research, said in a statement. “It’s incredibly exciting to know that everything will be rewritten. That’s one of the best parts of being a scientist.”
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Stay tuned. The Webb telescope will peer into the atmospheres of the extremely intriguing Trappist planets, seven rocky worlds that exist in the vicinity of a solar system that is neither too hot nor too cold. On some of these spheres, water may slide across the surface.