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Insight of the stars and planets


A study conducted in the lab shows that, the behavior of some noble gases, led to pressures and temperatures that simulate the interior of a giant planet or a star, it seems different from what we knew. The results could provide an explanation of the excess heat produced by a planet like Saturn. The article was published in PNAS.
The material they are made of stars and distant planets occurs under high pressure and extreme temperatures. Among the elements that make up this matter they are also observed the members of a particular family: that of the so-called noble gases. They are part of this group helium and neon, two names rather familiar. A recent study by a group of scientists led by Alexander Goncharov of the Carnegie Institution for Science has used laboratory techniques to simulate conditions that occur inside stars and planets, and observe how they behave the noble gases in these conditions. Thanks to this study we can better understand the atmospheric chemistry and interior of these celestial objects. The article will be published this week in the Proceedings of the National Academy of Sciences.

Alpha-stelle

Credit: STSCI/NASA

The team used a diamond anvil cell, a device that allows you to generate high pressures and to study the behavior of a material under such conditions, often referred to by the initials DAC: Diamond Anvil Cell, to bring the noble gases helium, neon, argon and xenon at pressures more than 100,000 times greater than that of Earth’s atmosphere (15-52 gigapascal). It has also been used a laser to heat the gases to extreme temperatures, up to about 28,000 ° C.
The gases are called “noble” because of a kind of chemical coldness: normally these gases do not combine with other elements. Have been studied with particular interest the changes in the ability to conduct electricity to vary the pressure and temperature, because these variations can provide important information about the ways in which the noble gases interact with other materials in extreme conditions, such as those present in the atmosphere planetary or stellar.
The insulators are those materials which do not allow leading to their interior a flow of electrons. The conductors, or metals, are materials that, on the contrary, may maintain an electrical current. The noble gases, when they are at ambient pressure, are not good conductors, but their conductivity can be induced creating conditions of higher pressure.
The research team, which included Stewart McWilliams (lead author) and Douglas Allen Dalton Carnegie, as well as Mohammad Mahmood Howard University and Zuzana Konopkova the Deutsches Elektronen-Synchrotron Photon Science in Hamburg, Germany, found that helium, neon, argon and xenon are transformed from insulators to conductors visually transparent visually opaque under varying conditions of pressure and temperature to values that simulate the interiors of stars and planets.
This has several interesting implications on the behavior of noble gases in the atmosphere and in the deeper layers of planets and stars.
For example, it could help solve the mystery of why Saturn emits more heat than would be expected. This behavior is related to the ability or inability of the noble gases to dissolve in the hydrogen liquid, present in abundance in giant planets like Saturn and Jupiter.
Inside Jupiter and Saturn helium may therefore result in an insulator in the vicinity of the surface, becoming conductor in the vicinity of the core of the planet. It seems that the transition from insulator to conductor happen in conditions of pressure and temperature to which also hydrogen, the main constituent of these planets, assumes the behavior of a conductor. It is expected that in fact both planets helium is dissolved in hydrogen and that the capacity of the two gases to mix is correlated with this type of transformation insulator-conductor.
However, there is a difference in the behavior of neon led to conditions that simulate the two gas giants. The team’s results show that the neon remain insulating even in an environment similar to the core of Saturn. If so, in the deep layers of the planet may be a layer of un-dissolved neon, preventing the erosion of the core of Saturn. In the case of Jupiter, however, the core materials, such as iron, would dissolve in the hydrogen surrounding liquid.
This lack of erosion of the core may explain why Saturn produces so much heat inside than its neighbor Jupiter. The erosion of the core of a planet leads to cooling of the planet itself, since the denser materials are transported upwards during mixing, converting heat in gravitational potential energy. On Saturn, however, the denser material could be collected at the center of the planet, making possible higher temperatures. The fact that Saturn give off a large amount of heat is a longstanding mystery. These findings could provide the key to solving it.
Another implication of this study involves the white dwarfs, dense and compact objects, and the result of the collapse of a star about the size of our sun when its life ends. Despite their high density, they are weakly bright as glowing emanating off their heat. We know that in the atmospheres of white dwarfs is helium, which may be located in the outer layers of some of these heavenly bodies. The conditions simulated in the laboratory indicate that this helium should be more opaque (and conductor) than expected previously and such opacity may slow the rate of cooling of white dwarfs rich in helium, in addition to influencing their color.

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