Thursday, October 1, 2009

COROT-7b: A Planet with Weather Worse than Minnesota's

"On Alien World, It Rains Rocks" (October 1, 2009)

"On Earth, strange things, including frogs and fish, sometimes fall from the sky, but on a distant extrasolar planet, the weather could be even weirder: When a front moves in, small rocks rain down on the surface, a new study suggests.

"The exoplanet, COROT-7b, was discovered in February by the COROT space telescope launched by the French and European space agencies. Last month is became the first planet outside our solar system to be confirmed as a rocky body — most other known exoplanets are gas giants.

"The planet is nearly twice the size of Earth and about five times the mass of our world. Calculations have indicated it has a density about that of Earth's, which means it is likely made up of silicate rocks, just as Earth's crust is.

"The planet is likely much less hospitable to life though, as it is only about 1.6 million miles (2.6 million km) away from its parent star — 23 times closer than Mercury sits to the sun...."

And, on the sunward (starward?) side of COROT-7b, it's hot enough to vaporize rock. That close to the star, it's almost certainly tidally locked, with one side always facing the star. It occurs to me that it might have a resonant rotation like Mercury's. The planet closest to our star rotates once every 2/3 of its year. The article doesn't mention this possibility, so I don't know if it's an omission, or something that's 'obvious.'

Anyway, COROT-7b's atmosphere is most likely - vaporized rock. The gasses would be mostly sodium, potassium, silicon monoxide and oxygen - either atomic or molecular oxygen.

Weather on COROT-7b should be pretty much like weather on Earth. Except that when a front comes through it rains rock.

"...The rock rains form similarly to Earth's watery weather: 'As you go higher the atmosphere gets cooler and eventually you get saturated with different types of "rock" the way you get saturated with water in the atmosphere of Earth,' [Washington University, St. Louis' Bruce Jr.] Fegley [Jr.] explained. 'But instead of a water cloud forming and then raining water droplets, you get a "rock cloud" forming and it starts raining out little pebbles of different types of rock.'..."

It's sort of nice to know that there's a place with weather more extreme than here in Minnesota.

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