Thursday, April 30, 2020

Inbox Astronomy: No Blue Skies for Super-Hot Planet WASP-79b


No Blue Skies for Super-Hot Planet WASP-79b

Release date: Apr 30, 2020 1:00 PM (EDT)

The 1927 song, "Blue Skies,' by celebrated American composer Irving Berlin, was an instant hit, and even featured in the very first Hollywood "talking picture," the Jazz Singer.

But if Berlin lived on the planet WASP-79b, he would only have had yellow skies for inspiration. This has piqued the curiosity of astronomers because it is so peculiar. The gas giant planet was expected to show evidence for Rayleigh scattering, a phenomena where certain colors of light are dispersed by very fine dust particles in the upper atmosphere. Rayleigh scattering is what makes Earth's skies blue by dispersing the shorter (bluer) wavelengths of sunlight.

This is a moot point regarding lyricist Berlin, because WASP-79b is a hellish class of planet that is unlike anything found in our solar system, or frankly, ever imagined by most astronomers. For want of a better word, astronomers simply call these planets "hot Jupiters." They are the size of Jupiter, or larger, but are so close to their star they complete one full orbit in a matter of days – or even hours. (At a distance of about 500 million miles from the Sun, Jupiter, by comparison, takes 12 years to complete an orbit.)

The term "hot" is an understatement. The planet WASP-79b has an atmospheric temperature of 3,000 degrees Fahrenheit, the temperature of molten glass. By combing observations from the Hubble Space Telescope, the Transiting Exoplanet Survey Satellite (TESS), and the ground-based Magellan observatory, astronomers found that the seething atmosphere is quirky. It is so hot that its scattered manganese sulfide or silicate clouds might rain molten iron. That is not the big surprise. But rather, the lack of Rayleigh scattering is just "weird," say researchers. It could be indicative of unknown atmospheric processes that aren't currently understood, and may yield clues to the planet's atmospheric evolution.

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