Exoplanet moons can help us find Earth's “habitable brothers”

Astronomers continue to study exoplanets in search of some “brother” of Earth, which has conditions for the existence of life. Now, a team of researchers suggests doing this search with a focus on exomoons, since natural satellites orbiting exoplanets can influence the habitability of those worlds — and they have identified a way to find them even in distant systems. Thus, the idea of ​​the study was not only to find these moons, but to determine their longevity, a characteristic that also influences the occurrence of conditions for life on these worlds.

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The new study featured Siegfried Eggl, professor assistant at the University of Washington, who points out that there is an average of moons orbiting the planets of the Solar System. “Thus, we suspect that moons exist around planets in other systems, as there is no reason why they should not exist,” he said. Recently, observations carried out with the Chilean Atacama Large Millimeter Array (ALMA) telescope showed what appears to be evidence of moons forming in the orbit of the planet PDS 70ç.

The PDS system , with detail that shows the planet and the circumplanetary disk that can form new moons (Image: Reproduction/ALMA/ESO/NAOJ/NRAO/Benisty)

Now, the next step is to find moons around planets with two stars, but the problem is that while planets from other star systems can be identified with large telescopes, moons are too small for that. “We know they are there, we just need to look better,” he commented. “Since it is very difficult to see them, we identified a way to detect them through the effect they have on the planet.”

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Researchers used the method of transit time variation (TTV) to search for moons in the Alpha Centauri system, made up of three stars and at least two planets. TTV collects measurements of the small forces that bodies exert on each other as they travel in their orbits; thus, when the planet passes in front of the star, it causes a small drop in its brightness. If there is another object exerting force on the planet, the time of this darkening will vary.

Also, if the planet has a moon, it will exert some force, which will cause the planet has a small movement, and this “flicker” may be enough to alter the time of dimming of the star’s light as the planet passes in front of it. Thus, if these small variations are detected, it is possible to obtain new information about the characteristics of the system. “This is indirect proof that there is a moon, because there is nothing else that can attract the planet in this way,” said the author.

To use the method, the researchers determined the resonances system orbitals they studied, and noted that when moons and planets have slightly elliptical orbits, they don’t always move at the same speed. However, they concluded that there was enough stability to motivate the search for exomoons orbiting planets in binary systems. Finally, Eggl considers that the results show that perhaps the Solar System is not as special as we like to think it is. “If we can use this method to show that there are other moons out there, there are probably other systems like ours,” he explained.

The article with the results of the study was published in The Astronomical magazine Journal.

Source: University of Illinois, Universe Today

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