Instruments track the results as high-intensity lasers set off a shock wave in a sample of magnesium oxide.
Credit: Eugene Kowaluk, University of Rochester

Cooling metal oxides could cause expanding exoplanets

At high enough temperatures, the oxides form a metal-like liquid, too.

by John Timmer – Nov 23 2012, 2:00pm EST

For many years, planetary scientists only had to worry about trying to understand the conditions that prevailed in the handful of planets in our Solar System: some small, rocky planets, a couple of ice giants, and a pair of gas giants. But we’ve now found hundreds of planets orbiting other stars, and the range of potential conditions has expanded dramatically with super-Earths, hot Jupiters, and thawed-out versions of the ice giants. If the conditions near the Earth’s core seem foreign to us, consider what it would be like at the core of a hot super-Jupiter, orbiting closer to its star than Mercury does to our Sun.

To understand the conditions that prevail on these exoplanets, we may have to rethink the properties of some of their constituent materials which will be found at pressures and temperatures unlike any we’ve seen. To get a better understanding of this, researchers have exposed a simple metal oxide (magnesium oxide, MgO) to extremely high pressures and temperatures. They found two distinct phase transitions: one that shrank the material’s volume by seven percent and a second that converted it into a metallic liquid, sufficient to drive the dynamos that generate magnetic fields.

Read more: Cooling metal oxides could cause expanding exoplanets | Ars Technica.

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