An international team of researchers led by Mungo Frost of the SLAC Research Center in California has gained new insights into the formation of diamond rain on icy planets such as Neptune and Uranus using the X-ray laser Europe's XFEL in Schenfeld. The results, now published in the scientific journal Nature Astronomy, also provide clues to the formation of these planets' complex magnetic fields.
In earlier X-ray laser studies, scientists have found that diamonds should form from carbon compounds found in large gas planets due to the high pressure prevalent inside them. These carbon compounds then sink further into the planet's interior, becoming a rain of gems from above.
A new experiment at Europe's XFEL has now shown that the starting pressure and temperature at which carbon compounds form diamonds are both lower than assumed. For gas planets, this means that diamond rain forms at lower depths than thought, and therefore may have a greater impact on the formation of magnetic fields. In addition, diamond rain may also form on gaseous planets smaller than Neptune and Uranus, which are called "little Neptunes". No such planet exists in the solar system, but such exoplanets do exist outside the solar system.
As diamond rain flows from the outer layer of the planet to the inner layer, it will entrain gas and ice, causing conductive ice flows. The current in a conducting fluid acts like a generator through which the planet's magnetic field is formed. "Diamond rain may have an impact on the formation of complex magnetic fields on Uranus and Neptune," Frost said.
The research team used plastic films made from the hydrocarbon polystyrene as a carbon source. Under extremely high pressure, diamond forms from the film - the same process that occurs inside planets, and which the European XFEL can mimic. Researchers used diamond extrusion units and lasers to generate the high pressure and temperature of more than 2,200 degrees Celsius that is common inside ice giant planets. The facility functions like a small pliers, with the sample squeezed between two diamonds. With the help of European XFEL X-ray pulses, the timing, conditions and sequence of diamond formation in the squeeze can be precisely observed.
The international research team also includes scientists from XFEL Europe, DESY Research Center Hamburg and the Helmholtz Center Dresden-Rosendorfer, as well as scientists from other research institutions and universities in different countries. The European XFEL Users Alliance HIBEF (including HZDR and DESY research centers) made a significant contribution to this work.
"Through this international collaboration, we have made huge progress at European XFEL and gained new insights into icy planets," Frost said.
Compiled source: ScitechDaily