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New experiments give insight into super Earth exoplanet cores

A Super Earth planet is one larger than Earth, but smaller than Neptune, the next largest planet in our solar system. Scientists have so far discovered over 2,000 Super Earth planets and are working to gain insight into the nature of the core hidden in the planets. The key to learning about these planetary cores is to study how iron and silicon alloys react to high pressures.

Since we can not travel to these superplanets to do experiments, the work has to be done in laboratories. A Princeton University laboratory uses techniques that allow access to extreme pressures found deep inside exoplanets and measure key properties found there. The work produced the highest pressure X-ray diffraction data ever recorded, and was led by a researcher at Princeton called June Wicks.

The team says that the internal pressure of a planet above the Earth could reach more than ten times the pressure in the center of the earth. In this study, the techniques used delivered pressures of up to 1

,314 gigapascals, which is about three times higher than in previous experiments. The team finds that most experiments use diamond anvils that can generate pressures of 300 GPa.

That's about 3 million times the pressure on the earth's surface. Pressures in the Earth's core reach up to 360 GPa. In the lab, the researchers compressed two samples for a few billionths of a second, giving them time to study the atomic structure with a pulse of bright X-rays. The generated diffraction provided information about the fate and crystal structure of iron silicon.

Wicks and her team steered a short, intense laser beam at two iron samples, one of which had 7 percent by weight silicon, which should be similar to Earth's vein. Another was 15% by weight silicon, which was possible in exoplanetary cores. Using this experiment, the researchers were able to calculate the density and pressure distribution within super-earths for the first time, taking into account the presence of silicon in the core. In the future, the team will investigate how other light chemical elements affect iron under extremely high pressure conditions.

SOURCE: Princeton

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