Taking Time

Getting to know an exoplanet takes time. As an example, consider a planet in the constellation Ophiuchus. Astronomers have compiled quite the dossier on the planet. But they still have a lot to learn.

Gliese 1214b orbits a red dwarf — a cool, faint cosmic ember. The system is about 48 light-years away. That’s close by astronomical standards, which is one reason the planet has attracted so much attention.

It was discovered in 2009. It passes in front of its star once every 1.6 days, blocking some of the star’s light. That’s allowed astronomers to measure its size: a little less than three times the diameter of Earth. And they’ve used another technique to figure out the planet’s mass: a bit more than eight times Earth’s mass.

As the planet passes in front of its star, some of the starlight filters through its atmosphere. That’s provided some hints about the atmosphere’s composition. But the atmosphere is topped by a thick haze, so astronomers can’t see what’s underneath.

One recent study posited that the planet itself is dense and heavy, like Earth, with a big iron core. It’s topped by an atmosphere of hydrogen and helium that’s thousands of miles thick, and could have changed little since the planet was born.

But other scientists have proposed other models — including some in which the planet has a lot of water. So it’s going to take a lot more time to really get to know Gliese 1214b.
 

Script by Damond Benningfield