The internal structure of the outer planets of the solar system is still a mystery to astronomers. In the case of Jupiter, NASA's Juno space probe is helping solve this mystery. And in the terrestrial laboratory, researchers have discovered clues that allow you to look deep inside the ice giants Neptune and Uranus. And it turned out that there can be diamond rains there.
An international team of researchers was able to show that hydrocarbon compounds are splitting inside the giant ice planets - Neptune and Uranus. This turns the carbon into a "diamond rain".
Scientists at the Helmholtz Center in Dresden-Rossendorf (HZDR), in collaboration with their German and American colleagues, were able to show that "diamond rains" form inside the ice giants of our solar system. With the help of ultra-high-power X-ray lasers and other facilities at the Stanford National Accelerator Laboratory (SLAC) in California, they simulated the internal structure of space giants. Thanks to this, scientists were able for the first time in real time to observe the decomposition of hydrocarbons and the transformation of carbon into diamond.
A solid core wrapped in dense layers of "ice" - this is how the internal structure of the planets Neptune and Uranus looks like. Such space ice is composed primarily of hydrocarbons, water and ammonia. And for a very long time, astrophysicists have been inclined to think that the extremely high pressure, which prevails here at depths of about 10 thousand kilometers, leads to the decomposition of hydrocarbons. In this case, diamonds are formed, which plunge further into the depths of the planets.
“Until now, no one has been able to observe such brilliant precipitation in a direct experiment,” says Dr. Dominik Kraus from HZDR. But it was in this that he and the international group of researchers led by him succeeded. "In the course of our research, we placed a special form of plastic - polystyrene, which is based on a mixture of carbon and hydrogen, in conditions similar to those existing inside Neptune and Uranus."
To achieve the desired effect, they sent two shock waves through the samples, excited by extremely powerful optical lasers in combination with an SLAC X-ray source called Linear Coherent Light Source (LCLS). As a result, the plastic was compressed under a pressure of about 150 Gigapascals at a temperature of about 5,000 degrees Celsius. “The first, weaker and slower wave was overtaken by the more powerful second wave,” explains Kraus. "And it is at the very moment when both waves intersect that most diamonds are formed."
Since this only lasts a fraction of a second, the researchers used high-speed X-ray defraction, which provided them with a snapshot of diamond formation and chemical processes. "Experiments show that almost all carbon atoms combine into nanosized diamond structures," sums up the scientist from Dresden. Based on the results, the authors of the study suggest that diamonds on Neptune and Uranus form significantly larger structures and slowly settle in the core of the planet over thousands and millions of years.
"From the experimental data we have received, we can also glean information that will allow us to better understand the structure of exoplanets," says Kraus of the prospects. For such space giants outside the solar system, researchers can measure only two parameters: the mass, which is determined from the positional oscillations of their parent star, and the radius, which astronomers derive from the dimming that occurs when the planet transits in front of the stellar disk. The relationship between the two values allows you to get the initial data on the chemical structure, for example, whether the planet consists of light or heavy elements.
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“And the chemical processes inside the planets tell us aspects that allow us to draw conclusions about the basic properties of these celestial bodies,” continues Kraus. “Thanks to this, we can improve and improve the planetary models already existing in science. Studies show that modeling is not yet a particularly accurate method."
But along with astrophysical knowledge, experiments can also have practical value. For example, nanodiamonds formed during experiments can be used for electronic instruments and in medical technology, as well as cutting materials in industrial production. So far, artificial diamonds are made using explosions. But making them using laser technology will make such production cleaner and more controlled.
The scientists wrote about the results of the research in an article published in the journal Nature Astronomy.