Hot Giants

Astronomers have discovered thousands of planets in other star systems. So far, they’ve found very few worlds that are even close to matching our own planet Earth.

But they have found a whole bunch of planets that are interesting because they’re completely different from Earth.

Among those are members of a class known as hot Jupiters. They’re at least as massive as Jupiter, the giant of our own solar system — and in some cases dozens of times heavier. But while Jupiter is almost 500 million miles from the Sun, hot Jupiters are just a few million miles out. At that range, they’re heated to thousands of degrees.

One example is Kepler-13Ab, the only planet known to orbit the star Kepler 13A. The planet is more than six times Jupiter’s mass and half-again its width. It’s only a couple of million miles from the surface of its star, which is hotter than the Sun. At that range, the planet’s cloudtops are heated to about 5,000 degrees Fahrenheit.

Kepler 13-Ab is locked so that one hemisphere always faces its star. But the atmosphere moves around the planet. On the cooler nightside, clouds of titanium dioxide form high in the sky — the main ingredient in sunscreen. Snow falls from the clouds, passing deep into the atmosphere.

As those clouds rotate into the daylight, though, they vaporize in the intense heat — a cycle that repeats over and over as this hot giant orbits its bright star.

We’ll talk about an even hotter planet tomorrow.

Script by Damond Benningfield

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