Humans haven’t yet figured out how to travel to other star systems to study exoplanets up close. But NASA has accomplished the next best thing—recreating the atmospheres of bizarre alien worlds right here on Earth.
Researchers at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, have succeeded in cooking up a simulated version of a “hot Jupiter.” These worlds are similar in scale to Jupiter, but orbit much closer to their stars than any planet in our solar system, with years that last no longer than 10 days. As a result, the atmospheres of hot Jupiters can reach searing temperatures exceeding 2,800°C (5,000°F).
A team led by JPL research scientist Benjamin Fleury created similar conditions in a laboratory using a recipe of hydrogen and a tiny pinch of carbon monoxide gas. (Carbon and hydrogen gas are extremely common materials in planet formation.)
Fleury and his colleagues heated the mixture up to 1,100°C (2,000°F) in an oven-like contraption. The team blasted the gas with UV and optical radiation with a lamp placed next to a window into the oven. This technique was designed to probe the photochemistry—the chemical effects of light—in the atmospheres of these planets.
The results present the “first laboratory experimental simulation of photochemistry in carbon-rich exoplanet atmospheres at elevated temperatures,” according to a study by Fleury’s team published in The Astrophysical Journal.
When the simulated hot Jupiter was exposed to these high temperatures and faux-starlight beams, its brew of hydrogen and carbon monoxide partially transformed into water and carbon dioxide. This corroborates past observations of water vapor in the atmospheres of hot Jupiters, and suggests that water might be more common on these planets than previously assumed.
The photochemical reactions also catalyzed the formation of aerosols, which are thick condensates that cause atmospheric haze. Aerosols have been detected in real hot Jupiters, but their role in producing the opaque appearance and atmospheric dynamics of the exoplanets is not well-understood.
"This result changes the way we interpret those hazy hot Jupiter atmospheres," said Fleury in a JPL statement on Thursday. "Going forward, we want to study the properties of these aerosols. We want to better understand how they form, how they absorb light and how they respond to changes in the environment.”
“All that information can help astronomers understand what they're seeing when they observe these planets," Fleury added.
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