The atmosphere of a young exoplanet didn't fit any of our existing models for what gas giants should look like. But when astronomers added huge dust clouds, it was a perfect fit, perhaps revealing a larger truth about gas giants.


The planet in question is HR 8799 b, a gas giant about seven times the mass of Jupiter. It's one of three gas giants revolving around the star HR 8799, located about 1,300 light-years away. The system was first discovered in 2008, and now astronomers have been able to perform spectroscopic analysis of the planets. These analyses are extraordinarily powerful, giving us close approximations of the planet's chemical composition, cloud properties, and even temperature.

We can figure out the temperature of an exoplanet by measuring the amount of methane in its atmosphere. According to the almost non-existence methane levels on HR 8799, its temperature couldn't be any cooler than about 1700 degrees Fahrenheit. But other metrics, such as the planet's apparent youthful age and the amount of energy it's sending out, suggest it should be about 250 degrees cooler than that, assuming our current models are right.


As it turns out, our models are wrong, or at least they didn't take into account the possibility of massive dust clouds on HR 8799 b. When those clouds are added into the equation, the data fits together perfectly and explains the 250 degree swing. Because this particular gas giant is one of the youngest we've ever observed and analyzed, it's quite possible that this extreme dustiness is just a natural part of a gas giant's infancy, which tells us something about the beginnings of our own solar system's four gas giants.

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[arXiv]