About which planets can we find moons that might contain life? A team of astronomers has compiled a ranking of the top contenders.
Meanwhile there More than 5,000 exoplanets have been discovered† Planets that orbit a star other than our Sun. But in the first confirmation discover exomán – A moon around an exoplanet – we’re still waiting. After astronomers Vera Dubos (University of Groningen) and colleagues have already tried You can find it abroad Which exoplanet has the greatest chance of having a habitable moon.
Outside the habitable zone
If you want to know if life is possible on a particular planet or moon — at least, life as we know it here on Earth — you have to see if there can be liquid water. With the planets, you depend on the so-called habitable areaA ring-shaped region around a star where the weather is neither too cold nor too hot. Thus, an outer moon orbiting a planet in the habitable zone could harbor liquid water—and thus life.
But a planet outside the habitable zone could also have a habitable moon. “If the moon gets close to its planet and has an elliptical orbit, it will experience tidal forces,” says Dubos. “This leads to friction on the inside of such a moon, which leads to the release of heat.” The heat that can make liquid water is also possible.
100,000 moons per planet
To determine which planets would likely have such a habitable moon, Dubos and her team first looked at the full list of known exoplanets. They removed planets associated with Ultra-bright stars to generate energy through nuclear fusion, the overweight planets, and the planets about which we know too little to be able to say a lot of meaning about them. After that they had 4140 left.
For each of these planets, they simulated 100,000 imaginary moons with random characteristics. Then, based on the amount of energy they received, they looked at how many 100,000 moons could contain liquid water. They called the ratio between the number of habitable satellites and the total number of satellites The possibility of the moon inhabitingOr the possibility of living on the moon. In other words, if 10,000 out of 100,000 simulated moons orbiting a planet could contain liquid water, then, according to the simulations, the probability of habitation on the planet’s surface was 10 percent.
Not from top to bottom
Based on the habitability probability of any moons, the researchers then put together an arrangement that can be found at the end of their article. At the top is the planet Kepler-459b, with a probability of at least 70 percent. In second place is the Kepler-456 b (shown in the illustration above), with 69 percent. It is followed by the HD 7199 b at 60%. You can find the complete list In this pdf file on page 7†
So does that mean astronomers looking to find habitable outer moons have to work through the list from top to bottom? No, says Dubos. I left this option to the scientists who gladly read the article. “They have to determine for themselves the targets that are most suitable for them, based on the monitoring techniques they use.”
Moons as big as Earth
And what makes exomoons so interesting that we’re already talking about their habitability, even before the first specimen was found? “Anyway, it’s very exciting to find a habitable world, whether it’s a planet or a moon,” says Dubos. “And if you also include moons, you greatly increase the number of places where life can be found. The most likely scenario is that there are more moons than planets. Moreover, there is no reason to believe that those moons cannot be as large as Earth. .”
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