JPL: For Hottest Planet, a Major Meltdown

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JPL: For Hottest Planet, a Major Meltdown

Post by bystander » Sat Jan 25, 2020 4:49 pm

For Hottest Planet, a Major Meltdown
NASA | JPL-Caltech | 2020 Jan 24

In the scorching atmosphere of exoplanet KELT-9b, even molecules are torn to shreds.

Artist's rendering of a "hot Jupiter" called KELT-9b, the hottest known exoplanet -
so hot, a new paper finds, that even molecules in its atmosphere are torn to shreds.
Credit: NASA/JPL-Caltech

Massive gas giants called "hot Jupiters" - planets that orbit too close to their stars to sustain life - are some of the strangest worlds found beyond our solar system. New observations show that the hottest of them all is stranger still, prone to planetwide meltdowns so severe they tear apart the molecules that make up its atmosphere.

Called KELT-9b, the planet is an ultra-hot Jupiter, one of several varieties of exoplanets - planets around other stars - found in our galaxy. It weighs in at nearly three times the mass of our own Jupiter and orbits a star some 670 light-years away. With a surface temperature of 7,800 degrees Fahrenheit (4,300 degrees Celsius) - hotter than some stars - this planet is the hottest found so far.

Now, a team of astronomers using NASA's Spitzer space telescope has found evidence that the heat is too much even for molecules to remain intact. Molecules of hydrogen gas are likely ripped apart on the dayside of KELT-9b, unable to re-form until their disjointed atoms flow around to the planet's nightside.

Though still extremely hot, the nightside's slight cooling is enough to allow hydrogen gas molecules to reform - that is, until they flow back to the dayside, where they're torn apart all over again. ...

Evidence for H2 Dissociation and Recombination Heat Transport in the Atmosphere of KELT-9b ~ Megan Mansfield et al
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