European scientists discovered atmospheric water on a planet 124 light years from us. The planet is within what astronomers call the habitable zone, with a temperature that could allow life to thrive there.
The rocky planet is eight times the mass of Earth and is known as a super-earth. This is the name given to planets between the size of Earth and Neptune. “Super-Earths are actually the most common type of planet in our galaxy,” said Ingo Waldmann, an extrasolar planet explorer at University College London, UK. Super-Earths are also possible residences of alien life.
The first planet to orbit an active star beyond our own solar system was discovered in 1995 . Since then, the Kepler space telescope has increased the rate of discovery, with 4,000 such exoplanets now known. Initially, the large gas giants near their stars, “hot Jupiters,” seemed more common, but as more and more super-Earths accumulated, scientists were baffled by their abundance.
“The first exoplanet systems found were simple, with a hot Jupiter orbiting a star. We weren’t really expecting anything like super-Earths, but then they started showing up, “explains Waldmann.” We know next to nothing about super-Earths at this point, because they don’t exist in our own solar system. “
Diversity
Most of these mysterious planets are discovered when they pass in front of small stars and cause the starlight to dim. From this, researchers can calculate the mass and radius of the planet and the evidence suggests that these worlds are incredibly diverse in their composition.
“Super-Earths can be all kinds of things,” Waldmann clarifies. Give the example of 55 Cancri e, a planet with an ocean of lava at temperatures high enough to melt iron, and Gliese 1214 b, which is a potential ocean planet consisting mainly of water. Scientists deduce which molecules are in a planet’s atmosphere by studying the light from the stars in their path.
Knowing what goes on inside these distant planets is much more difficult. “We can look at the surface of the star to obtain clues about the chemistry and composition of a planet, which gives us clues about the amount of iron or silicon that can be in a planet”, explains Razvan Caracas, planetary mineralogist at the École Normale. Supérieure de Lyon in France.
This is important because depending on whether there is a solid core, perhaps made of nickel or nickel and iron, and an outer core of liquid metal, a planet may or may not have a magnetic field. The Earth’s magnetic field keeps most of the solar radiation away from us by diverting a stream of charged particles from reaching the surface of our planet. The researchers believe that this kind of protection would be necessary for life to emerge elsewhere.
Caracas oversaw a project called ABISSE that ran computer simulations of various iron-nickel mixtures at extremely high pressures to see how they behaved. These are the metals likely to be found in the core of super-Earths, but it is unclear whether iron and nickel would mix, separate into different layers, or become liquid under the intense pressures within the large planets.
By understanding the type of core structure that could arise from nickel and iron ratios, scientists hope to understand what might be happening inside super Earths based on what we find out about their chemical makeup.
Protection
“Two nuclei could behave differently, and one could have a magnetic field and the other could not,” explained Caracas. “A stronger magnetic field gives it better protection on the surface from the sun’s rays, and that means it can produce organic molecules that are more complex.”
Guillaume Fiquet, an experimental physicist at the CNRS and the Sorbonne University in Paris, France, is also trying to understand the interiors of the super Earth through a project called PLANETDIVE. “When people talk about the habitability of planets, it is often related to the presence of a magnetic field, which in turn is related to having some kind of metallic core or at least conductive material (in vigorous motion),” he said. .
He is investigating how materials such as iron behave under pressures within super-earths, which could be up to 1 terapascal, three times the pressure within Earth. This crushes atoms and can change the properties of materials, which means that our knowledge of how they behave on Earth may not apply to exoplanets.
“Exoplanets can be planets larger than Earth, which means that pressures and temperatures could be much higher,” says the expert. ” That forces us to try to develop new tools to access special states of matter that we do not yet know.”
Fiquet sheds light on this mystery by recreating the extreme high temperatures and pressures that can be at the heart of these exotic planets. It does so on smaller and smaller scales, firing powerful lasers at tiny pieces of metal or squeezing them between microscopic diamond anvils.
This experimental setup has helped him draw melting curves for elements like iron that are likely to be found in the core of Super Earths under intense pressure. These can then be used to refine the properties of materials that scientists use to infer what goes on inside super Earths and ultimately learn more about their bulk chemical makeup.
Meanwhile, Waldmann is leading the research to help astronomers deal with super-Earth data from future exoplanet discoveries using artificial intelligence (AI). We need artificial intelligence, Waldmann explains, “because all this data is extremely difficult to analyze and we will be at the limit of what is possible to do by hand.”
Super-Earths are the main candidates for the existence of extraterrestrial life. Its AI, developed through the ExoAI project, will help astronomers interpret observations of chemicals in the atmosphere of an exoplanet, for example, and tell them whether or not a super-Earth is interesting for further study.
“That’s the holy grail,” Waldmann added. “Finding chemical signatures in the atmosphere of a super-Earth due to life. Hopefully we will in the next few years or decades. “
Original article
This article was originally published in Horizon, the EU Research and Innovation Magazine
