In the high pressure physics labs of Sandia in New Mexico, hides one of the most powerful pulsed X-ray generators in the world: the Z machine. And recently, a team of researchers used the capabilities of the instrument to simulate the temperature and pressure conditions prevailing within exoplanets known as super-Earths. The aim of this experiment was to determine the planetary conditions most favorable to the maintenance of a geophysical activity - in particular concerning the atmosphere - compatible with life. The data obtained by the physicists made it possible to draw up a list of seven candidate super-Earths deserving of further study.
The enormous forces generated by the Z machine at Sandia National Laboratories are used to replicate the gravitational pressures of "super-Earths" to determine which ones could sustain atmospheres suitable for life. Astronomers believe that super-Earths - rocky planets up to ten times the size of Earth - exist in the millions in our galaxy . “ The question before us is whether any of these super planets are actually Earth-like, with active geological processes, an atmosphere and a magnetic field, ” says Joshua Townsend, physicist at Sandia.
The work is described in the journal Nature Communications . Researchers in Sandia's Basic Science Program, working with colleagues at the Earth and Planets Laboratory at the C arnegie Institution for Science, use the forces of Sandia's powerful and unique Z machine to almost instantly apply the equivalent of enormous gravitational pressures to bridgmanite, also known as magnesium silicate, the most abundant material in solid planets.
In the high pressure physics labs of Sandia in New Mexico, hides one of the most powerful pulsed X-ray generators in the world: the Z machine. And recently, a team of researchers used the capabilities of the instrument to simulate the temperature and pressure conditions prevailing within exoplanets known as super-Earths. The aim of this experiment was to determine the planetary conditions most favorable to the maintenance of a geophysical activity - in particular concerning the atmosphere - compatible with life. The data obtained by the physicists made it possible to draw up a list of seven candidate super-Earths deserving of further study.
The enormous forces generated by the Z machine at Sandia National Laboratories are used to replicate the gravitational pressures of "super-Earths" to determine which ones could sustain atmospheres suitable for life. Astronomers believe that super-Earths - rocky planets up to ten times the size of Earth - exist in the millions in our galaxy . “ The question before us is whether any of these super planets are actually Earth-like, with active geological processes, an atmosphere and a magnetic field, ” says Joshua Townsend, physicist at Sandia.
The work is described in the journal Nature Communications . Researchers in Sandia's Basic Science Program, working with colleagues at the Earth and Planets Laboratory at the C arnegie Institution for Science, use the forces of Sandia's powerful and unique Z machine to almost instantly apply the equivalent of enormous gravitational pressures to bridgmanite, also known as magnesium silicate, the most abundant material in solid planets.
Identify super-Earths conducive to the emergence and evolution of life
The experiments gave rise to a data-driven chart showing when and within what time range a planet's interior would be solid, liquid, or gaseous under various pressures, temperatures and densities. Only a liquid core - with metals moving over each other under conditions resembling those of an Earth's dynamo - produces the magnetic fields that can deflect solar winds and cosmic rays from a planet's atmosphere, allowing life to emerge.
This critical information on the magnetic field intensities produced by the core states of super-Earths of different sizes was previously unavailable: the nuclei are well hidden within the planets, and therefore not visible by direct observation from a distance. For researchers who preferred terrestrial experiments over long-range imaging, sufficient pressures were not available until the capabilities of the Z machine were mobilized.
Further analysis of the state of gaseous and dense materials on specific super-Earths has produced a list of seven planets that may merit further study: 55 Cancri e; Kepler 10b, 36b, 80e and 93b; CoRoT-7b; and HD-219134b. The emphasis is on oversized planets rather than smaller planets, because strong gravitational pressures mean atmospheres are more likely to be sustained over the long term.
Sandia Director Christopher Seagle explains, “ These planets, which we have found to be the most likely to support life, were selected for further study because they have similar ratios to Earth at the iron level, their silicates and their volatile gases, in addition to the internal temperatures conducive to the maintenance of magnetic fields for protection against the solar wind ”.
For these experiments, the Z machine, with operating conditions of up to 26 million amperes and hundreds of thousands of volts, creates magnetic pulses of tremendous power that accelerate pieces of copper and aluminum from the size of a credit card, called "hang plates".
The Z machine generates powerful pulsed X-rays to accelerate copper and aluminum plates, with the aim of propelling them at high speed into particular targets. The waves resulting from the collision give physicists precise information about the behavior of the material under test. © Randy Montoya
These were propelled much faster than a rifle bullet into samples of bridgmanite, the most common mineral on Earth. The almost instantaneous pressure of the artificial interaction created longitudinal and transverse sound waves (similar to seismic waves) in the material, which reveal whether it remains solid or turns into a liquid or a gas. With these new results, researchers have obtained solid data on which to anchor otherwise theoretical planetary models.
The technical paper concludes that the high precision density data and unprecedented melting temperatures achieved by the Z machine provide benchmarks for theoretical calculations under extreme conditions. “ This work identifies interesting exoplanet candidates for further exploration. Z shock compression and the researchers' ability to synthesize large diameter bridgmanite provide an opportunity to obtain relevant data for exoplanets that would not be possible anywhere else,