New experiments give insight on super-Earth exoplanet cores

A super-Earth planet is one that is larger than Earth but smaller than Neptune, which is the next largest planet in our home solar system. Scientists have so far discovered over 2,000 super-Earth planets and have been working to gain insights into the nature of the core hidden away inside the planets. Key to learning about these planet cores is to study how iron and silicon alloys respond to high pressures.

Since we can't travel to any of these super-Earth planets to conduct experiments, the work has to happen in labs. A lab at Princeton University has been using techniques that allow access to extreme pressures found deep in the interior of exoplanets and measure key properties that would be found there. The work created the highest-pressure X-ray diffraction data ever recorded and was led by an associate research scholar at Princeton called June Wicks.

The team says that the interior pressure of a super-Earth planet could reach more than ten times the pressures at the center of the Earth. In this study, the techniques the team used delivered pressures up to 1,314 gigapascals, which is about three times higher than was achieved in previous experiments. The team notes that most experiments use diamond anvils able to produce pressures of 300 GPa.

That is about 3 million time the pressure at the surface of the Earth. Pressures in the core of the Earth reach up to 360 GPa. In the lab, the researchers compressed two samples for a few billionths of a second giving them enough time to probe the atomic structure using a pulse of bright x-rays. The diffraction created gave information on destiny and crystal structure of the iron-silicon allows.

Wicks and her team directed a short, intense laser beam onto two iron samples with one have 7 weight-percent silicon said to be similar to the Earth's core. Another was 15 weight-percent silicon thought to be possible in exoplanetary cores. Researchers were able for the first to calculate density and pressure distribution inside super-Earths taking into account the presence of silicon in the core thanks to this experiment. In the future, the team will investigate how other light chemical elements affect iron at ultrahigh pressure conditions.

SOURCE: Princeton