The planetary formation of super-Earths around alien suns has been recreated by scientists, using powerful lasers to model the immense heat and pressures inside these giant worlds. This research could also help astronomers understand some of the geological processes that took place during the formation of Uranus and Neptune, the two giant frozen globes within our own family of planets.
Exoplanets are likely to possess rocky cores, surrounded by subsurface oceans of liquid magma, the experiment revealed. Super-Earths contain up to 10 times as much matter as does our own home planet. This extra mass results in greater gravitational forces than we experience here, creating massive pressures, pressing into the center of the worlds.
Researchers from Lawrence Livermore National Laboratory focused a series of lasers on a small sample of stishovite, a form of silica, a common ingredient in rocky planets. The greatest amount of pressure ever applied to a material under laboratory conditions was around 100,000 gigapascals, roughly one million times average air pressure at sea level. Application of focused bursts of laser energy resulted in pressures five times greater than ever seen before. These pressures are believed to be comparable to those experienced by materials between the core and mantle of a planet five times more massive than the Earth. Researchers found that at these tremendous pressures, the melting point of silica rose dramatically, from approximately 3,000 degrees to around 14,480 degrees Fahrenheit.
"Stishovite, being much denser than quartz or fused-silica, stays cooler under shock compression, and that allowed us to measure the melting temperature at a much higher pressure," Marius Millot of Bayreuth University in Germany, said.
This research suggests that layers of molten rock may exist for long periods of time, and could potentially drive powerful planetary magnetic fields.
"Deep inside planets, extreme density, pressure and temperature strongly modify the properties of the constituent materials. How much heat solids can sustain before melting under pressure is key to determining a planet's internal structure and evolution, and now we can measure it directly in the laboratory," Millot said.
Jupiter and Saturn could also possess solid silica deep within their solid bodies, the finding revealed.
Over 1,000 planets have been confirmed orbiting other suns, exhibiting a wide range of sizes, masses and other properties, revealing a more dynamic range of possibilities than astronomers once thought possible. This new study could allow astronomers to accurately model the formation of large planets in our solar system and beyond.
The role of enormous pressures on the development of super-Earths was detailed in the journal Science.
