Hot Jupiter snows 'sunscreen'

Learning about planets outside our Solar System gives astronomers a broader view of the Universe. One of the latest discoveries is a huge, scorching planet on which it snows the main ingredient found in suntan lotion.

An artist’s concept of Kepler-13Ab orbiting its host star Kepler-13A. In the background can be seen the star’s binary companion, Kepler-13B, and the orange dwarf star Kepler 13C.
NASA, ESA, and G. Bacon (STScI)


Exoplanet scientists have discovered a ‘hot Jupiter’ about 1,730 lightyears from Earth that snows titanium dioxide, a main ingredient found in suntan lotion.

The hot Jupiter - so-called because it is similar in size to Jupiter but much closer to its host star - is known as Kepler-13Ab. The host star Kepler-13A is part of a multi-star system including star Kepler-13B, and dwarf star Kepler 13C.


Read more about hot Jupiters from BBC Sky at Night Magazine:


The exoplanet is tidally locked, which means the same side always faces its host star, just like the Moon around Earth. On its dayside, temperatures can reach as high as 2,700°C.

Kepler-13Ab only experiences the sunscreen snow on its darker side. Scientists studying the exoplanet suggest that winds carry titanium oxide gas to the colder nighttime side, where it condenses, forms as clouds and falls as snow.

The planet’s surface gravity is six times greater than Jupiter’s, which pulls the titanium oxide snow out of the upper atmosphere and traps it in the lower atmosphere.



An illustration showing how Kepler-13Ab compares with the planets of our Solar System.
NASA, ESA, and A. Feild (STScI)


The scientists behind the study found that Kepler-13Ab's atmosphere is cooler at higher altitudes; contrary to what was expected.

They inferred that a light-absorbing, gaseous form of titanium oxide was missing from the planet’s atmosphere on its dayside.

This causes the atmospheric temperature to grow colder at higher altitudes, whereas for hot Jupiters like this, the opposite would be expected.

The study is one of many seeking to learn more about exoplanets and their weather systems. By studying star systems beyond our own, astronomers hope to get a broader idea of the characteristics of the Universe.

"In many ways, the atmospheric studies we're doing on hot Jupiters now are testbeds for how we're going to do atmospheric studies on terrestrial, Earth-like planets," says lead researcher Thomas Beatty of Pennsylvania State University.

"Hot Jupiters provide us with the best views of what climates on other worlds are like. Understanding the atmospheres on these planets and how they work, which is not understood in detail, will help us when we study these smaller planets that are harder to see and have more complicated features in their atmospheres."

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