What do 'hot Jupiters' look like? Scientists say exoplanets may have clouds made of titanium or molten sand

For comparison, Earth has water vapor, and Venus has sulfuric acid and carbon dioxide


                            What do 'hot Jupiters' look like? Scientists say exoplanets may have clouds made of titanium or molten sand
(Getty Images)

Astronomers studying distant worlds or exoplanets predict that "hot Jupiters" --  which boast of extremely high temperatures  -- have exotic skies, far different from ours. These gas giants may have aluminum oxides and titanium or even molten sand hanging out in the clouds, predict scientists in a new study. For comparison, Earth has water vapor, and Venus has sulfuric acid and carbon dioxide. Hot Jupiters, known for their proximity to their stars, typically have temperatures anywhere between  800 and 3,500 degrees Fahrenheit. “The kinds of clouds that can exist in these hot atmospheres are things that we don’t really think of as clouds in the solar system,” said Peter Gao, a 51 Pegasi b Postdoctoral Fellow at the University of California, Berkeley, who is the first author of a paper describing the model in the journal Nature Astronomy.

In this study, researchers from the US, UK, and Canada have predicted the kind of clouds we can expect to see if a telescope manages to peek into the atmospheres of hot Jupiters. The team believes their work may help planetary scientists understand the atmospheres of cooler giant planets and their moons, such as Jupiter and Saturn’s moon Titan in our solar system.

Some clouds prevent scientists from probing atmosphere of distant planets 

Telescopes have peered through the atmospheres of several distant lands, providing scientists with information about them. For instance, experts have detected water, methane, carbon monoxide and carbon dioxide, potassium, and sodium gases and, in the hottest of the planets, vaporized aluminum oxide, iron, and titanium. By studying gases in an exoplanet, scientists can learn about the planet's origins and whether it can support life.

Predicted cloud altitudes and compositions for a range of temperatures common on hot Jupiter planets (UC Berkeley image by Peter Gao)

But not all distant lands are alike. Some of them have clouds that block light, preventing telescopes from picking up details about the planet. “We don’t really know what they are made of, but they are contaminating our observations, essentially making it more difficult for us to assess the composition and abundances of important molecules, like water and methane," Gao said in a statement. So Gao and team proposed these clouds may contain aluminum oxides, such as corundum, the stuff of rubies and sapphires; molten salt, such as potassium chloride; silicon oxides, or silicates, like quartz, the main component of sand; sulfides of manganese or zinc that exist as rocks on Earth; and organic hydrocarbon compounds.

They then used computer models to simulate conditions of cloudy atmospheres of planets like Jupiter. He later checked which chemicals were likely to form clouds across the temperature range of hot Jupiters. Gao and his team found that many of the proposed chemicals failed to form clouds at such high temperatures. But silicon clouds combined with oxygen is a possibility. They predict that planets at the lower temperature range may have clouds composed of hydrocarbon haze, essentially smog, while their hottest counterparts may have aluminum oxides and titanium.

Next, the team will have to confirm if hot Jupiters indeed have clouds made of these chemicals. They are hoping that NASA’s James Webb Space Telescope, scheduled to launch next year, answers the questions and perhaps shed light on the hidden cloud layers of planets closer to home.

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