Planets that can vaporise rock (and other stories)

October is planetary science month. That’s when the American Astronomical Society’s Division for Planetary Sciences holds its annual meeting, with hundreds of researchers discussing planetary bodies large and small. Want the latest on the search for Planet 9? Here’s the place to find out. (Hint: nobody’s found it.) Wondering what counts as a planet? Forget the controversy over Pluto. Planetary science welcomes objects that would fit tidily within a football stadium.

So what did we learn in this year’s meeting?

First and foremost, the proper name is Division for Planetary Sciences. Not “science” but “sciences”, and not “of” but “for”, as DPS chair Amy Mainzer, of the University of Arizona, said in a humorous welcoming address.

Her comedic riff underscored another thing: planets are fun.

Here’s a good example: we’ve all heard of rocky planets like Earth and Mars. But exoplanet WASP 76b has a rocky atmosphere, too.

More interestingly, it’s hot enough to vaporise rock.

Scientists already knew it was hot. It orbits so close to its star that its “year” is 1.8 Earth days, and its sun is hotter than ours. They’d also discovered it’s so hot it can vaporise iron and (probably) produce iron rain.

But vaporised rock? That’s hotter yet. Nevertheless, there appears to be a lot of ionised calcium (a common constituent of rocks) in its atmosphere, says Emily Deibert, a graduate student at the University of Toronto.

“That tells us the atmosphere is even more extreme than anticipated,” she says – possibly substantially hotter than 2200°K (~1900°C). To put that in context, that’s hot enough for its air to glow red-hot.

Among other matters, the DPS meeting heard about ‘missing’ Plutos, upcoming NASA exploratory missions, binary objects in the Kuiper Belt and how a successful failure gave scientists a better look at Jupiter’s moons than they could possibly have expected.

For a full wrap of the meeting, log in to Cosmos Weekly.

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