The pressure measured by recording EOS reveals the evolution of stars

Using a team of researchers and international collaborators from Lawrence Livermore National Laboratory, using the resources of the world’s highest energy laser system national ignition device, to control the highest pressure achieved in laboratory experiments so far, the experimental ability to measure the basic properties of substances, such as equation of state, was developed. < / P > < p > note: a composite image of a white dwarf in the NIF hohlraum. White dwarfs with solar mass are about the size of earth, making them one of the densest objects in space after neutron stars and black holes. These results are related to the core conditions of giant planets, the interior of brown dwarfs, the carbon envelope of white dwarfs, and many applied science programs of Lawrence Livermore National Laboratory. The authors of this group say that overlap with white dwarf inclusions is particularly important – this new study provides an experimental basis for the basic properties of matter in this system. The result will eventually lead to an improved white dwarf model, which represents the final stage in the evolution of most stars in the universe. < / P > < p > in billions of years, the sun and other low and medium mass stars will experience a series of expansions and contractions, leading to the formation of white dwarfs – stars that have run out of nuclear fuel and collapsed into a hot, ultradense mixture of carbon and oxygen. < / P > < p > in order to resolve the divergence of extreme pressures associated with white dwarfs and various laboratory research projects in the EOS model, scientists conducted the first laboratory study on a substance called & quot; hot DQ & quot; in the outer carbon layer of an abnormal white dwarf. < / P > < p > this study subjected solid hydrocarbon samples to pressures ranging from 100 to 450 MEGABARS to determine EOS in the troposphere of “hot DQ”. These are the highest pressures achieved in laboratory EOS measurements. “White dwarfs provide an important test of the physical models of stars, but the EOS models under these extreme conditions are largely untested,” said Annie kretscher, a physicist at Lawrence Livermore National Laboratory, the lead author of the paper < / P > < p > kretcher added: “NIFS can replicate conditions from the core of planets and brown dwarfs to the center of the sun.” “We are also able to infer the opacity of the shock along Hugoniot in the NIF experiment, which is an essential part of studying the evolution of stellar structures.” < p > < p > < p > the atmosphere of “hot DQ” is composed mainly of carbon, not hydrogen and helium, as most white dwarfs do, and is unusually hot and bright. Due to the magnetic field points on the surface, some sensors will also pulsate when rotating, thus providing a visible brightness change. The analysis of these variations “provides a rigorous test of the white dwarf model and provides a detailed picture of the results of the later stages of star evolution,” the researchers said However, the current EOS models associated with hundreds of millions of white dwarfs at atmospheric pressure may differ by nearly 10%, “which is a great uncertainty for stellar evolution models,” they added Kretcher said previous researchers called it “the weakest link in constitutive physics” and provided information for modeling white dwarfs. The difference can be solved by providing the first EOS data, which can reach the conditions deep in the “hot DQ” convection zone, where the model shows the greatest variability. The experimental results are consistent with the EOS model, which recognizes the extent to which the inner shell electrons can be stripped from their carbon atoms under extreme pressure, thus reducing the opacity and improving the compressibility of the ionized plasma. < / P > < p > “the nifdiscovery science program enables our diverse team of researchers from universities, national laboratories and industries to work together for a long time to understand fundamentally the behavior of substances under the most extreme pressures and temperatures.” “The NIF is the only facility in the world that can create and detect these conditions, and its expert support team is key to our success,” Falcone said. This paper highlights the power of this collaboration and provides evidence for how basic research finds applications in many fields, including astrophysics. ” < / P > < p > in the EOS experiment, the laser of nif transmits 1.1 million joules of ultraviolet light into the interior of a pencil sized hollow gold cylinder, forming a uniform X-ray “bath”, and the peak radiation temperature is close to 3.5 million degrees. X-rays are absorbed by a solid plastic ball mounted in the center. < / P > < p > the plastic is heated and ablated by X-rays, or blown away like rocket exhaust gas, which generates ablation pressure and emits a converging shock wave to the center of the target capsule at a speed of 150-220 km / s. These shocks combine into one more powerful shock, with a pressure of nearly a billion times that of the earth’s atmosphere. < / P > < p > the Hugoniot was identified using time and space resolved fringe X-ray photography. The results of the experiments at low temperature and ambient temperature and the change of laser pulse shape show consistent results. They also measured the electron temperature and ionization degree of the bulk shock material by X-ray Thomson scattering. < / P > < p > “we measured the decrease in opacity at high pressure, which is related to the significant ionization of the inner carbon shell.” “The pressure range along Hugoniot corresponds to the conditions in the carbon envelope of the white dwarf,” kretcher said. Our data are consistent with the equation of state model, including detailed electronic shell structure < / P > < p > she said that these models “show greater bending and higher maximum compression in Hugoniot” than those without an electronic case, implying a “softening” of EOS. This “pressure ionization” results in an increase in compression. < / P > < p > the researchers concluded that the experimental data can provide a better model for pulsating heat DQ stars, and more accurately determine their internal structure, pulsation characteristics, spectral evolution and complex origin. gather and watch! Huawei P40 Pro evaluation: excellent mobile phone photography elegant design, do you like it?